text:
\section*{\large Synopsis}

\noindent {\large \bf Synopsis}

One of
the most important recent developments in string theory is the discovery
of D-branes and a deeper understanding of their properties. Among other
things, this allows one to derive for the first time noncommutative
geometry from  string theory.
The resulting noncommutative geometry has stimulated a wide range of
physical applications and has leaded to new insights into a fundamental
formulation of string theory.

\section{Noncommutative Geometry from String Theory}

The first use of noncommutative geometry in string theory appears in the
work of Witten on open string field theory \cite{witten1} where the
noncommutativity is associated with the product of open string fields.
Noncommutative geometry appears in the recent development of string
theory in the seminal work of Connes, Douglas and Schwarz \cite{cds}
where they constructed and identified the compactification of Matrix
theory on noncommutative torus.

We refer the readers to
the textbooks \cite{connes,madore,landi,bond} for general references
on noncommutative geometry,
\cite{GSW,polchinski,cvj} for an introduction to string theory. And to
the excellent reviews \cite{trieste,harvey,schwarz-review,nd,szabo}
for an in-depth discussion of the physical aspects of the modern
development of noncommutative geometry in string theory, as well as for a
more comprehensive list of references.

\head{Matrix theory compactification and noncommutative geometry}
M-theory is an eleven dimensional quantum  theory
of gravity which is believed to underlie all superstring theories.
Banks, Fischler, Shenker and Susskind proposed that the large
$N$ limit of the supersymmetric  matrix quantum mechanics of $N$
D0-branes should describe the $M$ theory compactified on a light-like
circle \cite{bfss}. See also \cite{taylor-M-review} for review.
Compactification of Matrix theory on torus  can be easily achieved by
considering the torus as the quotient space $\mathbb{R}^d/\mathbb{Z}^d$ with the
quotient conditions
\begin{equation} \label{compact}
U_i^{-1} X^j U_i = X^j + \delta}\def\D{\Delta}\def\ddt{\dot\delta_i^j 2\pi R_i, \quad i = 1, \cdots, d.
\end{equation}
Here $R_i$ are the radii of the torus.
The unitary translation generators $U_i$  generate the torus.
They satisfy $U_i U_j = U_j U_i$.
T-dualizing the D0-brane system,
the equation \eq{compact} leads to the dual description as a
$(d+1)$-dimensional supersymmetric gauge theory on the dual toroidal
D-brane \cite{taylor-compact}. A
noncommutative torus $T^d_\theta}	\def\Th{\Theta}	\def\vth{\vartheta$ is defined by the modified relations
\begin{equation} \label{nc-T}
U_i U_j = e^{i \theta}	\def\Th{\Theta}	\def\vth{\vartheta_{ij}} U_j U_i,
\end{equation}
where $\theta}	\def\Th{\Theta}	\def\vth{\vartheta_{ij}$ specify the noncommutativity.
Compactification on noncommutative torus can be easily accommodated and
leads to noncommutative gauge theory \cite{connes-rieffel}
on the dual D-brane.
The parameters $\theta}	\def\Th{\Theta}	\def\vth{\vartheta_{ij}$  can be identified
with the components $C_{-ij}$ of the 3-form potential in M-theory.

Since M-theory compactified on a circle leads to IIA string theory, the
components $C_{-ij}$ corresponds to the Neveu-Schwarz (NS) B-field $B_{ij}$
in IIA string theory. The physics of the D0-brane system in the
presence of a NS $B$-field  \cite{cheung} can also be
studied from the view of IIA string theory. This lead Douglas and Hull
to obtain the same result that a noncommutative field theory lives
on the D-brane \cite{douglas-hull}. Toroidally compactified IIA string theory has a
T-duality group $SO(d,d;\mathbb{Z})$.
The T-duality symmetry got translated into
an equivalence relation between gauge theories on noncommutative torus
\cite{cds,schwarz-T,zumino-T}:
A gauge theory on noncommutative torus $T^d_\theta}	\def\Th{\Theta}	\def\vth{\vartheta$ is equivalent to
a gauge theory on noncommutative torus $T^d_{\theta}	\def\Th{\Theta}	\def\vth{\vartheta'}$ if
their noncommutative parameters and metrics
are related by the T-duality transformation. For example,
\begin{equation} \label{mor}
\theta}	\def\Th{\Theta}	\def\vth{\vartheta' = (A\theta}	\def\Th{\Theta}	\def\vth{\vartheta +B)(C \theta}	\def\Th{\Theta}	\def\vth{\vartheta +D)^{-1}, \quad
\left(\begin{array}{cc}A & B \\ C & D \end{array} \right) \in SO(d,d;\mathbb{Z}).
\end{equation}
It is remarkable that the T-duality acts within the field theory level,
rather than mixing up the field theory modes with the string winding
states and other stringy excitations.
Mathematically \eq{mor} is precisely the condition
for the noncommutative tori $T^d_\theta}	\def\Th{\Theta}	\def\vth{\vartheta$ and $T^d_{\theta}	\def\Th{\Theta}	\def\vth{\vartheta'}$ to be Morita
equivalent \cite{connes}.

\head{Open string in $B$-field}
It was soon realized that  the D-brane is not
necessarily to be toroidal in order to be noncommutative \cite{CH}.
A direct canonical quantization of the open string
system shows that a constant $B$-field on a D-brane leads to
noncommutative geometry on the D-brane worldvolume.
Consider an open
string moving in a flat space with metric $g_{ij}$ and a constant
NS $B$-field. In the presence of a D$p$-brane, the
components
of the $B$-field not along the brane can be gauged away and thus the
$B$-field can have effects only in the longitudinal directions along
the brane.  The worldsheet (bosonic) action for this part is
\begin{equation} \label{action}
S= \frac{1}{ 4\pi\alpha'} \int_{\Sigma} d^2\sigma
\bigl( g_{ij} \del_a x^i \del^a x^j - 2 \pi  \alpha}		\def\da{{\dot\alpha}' B_{ij} \epsilon^{ab}\del_a
x^i \del_b x^j \bigr),
\end{equation}
where $i,j=0,1,\cdots, p$ is along the brane.
It is easy to see that the boundary condition
$g_{ij} \del_\sigma}	\def\S{\Sigma x^j + 2 \pi i \alpha}		\def\da{{\dot\alpha}' B_{ij} \del_\tau x^j =0$
at $\sigma}	\def\S{\Sigma=0, \pi$ is not compatible with
the standard canonical quantization $[x^i(\tau,\sigma}	\def\S{\Sigma),x^j(\tau,\sigma}	\def\S{\Sigma')] =0$
at the boundary.
Taking the boundary condition as constraints and perform the
canonical quantization, one obtains the commutation
relations
\begin{equation}  \label{cr2}
[a_m^i, a_n^j]= m G^{ ij}\delta}\def\D{\Delta}\def\ddt{\dot\delta_{m+n},
\quad [x_0^i, p_0^j]=i G^{ ij}, \quad
[x_0^i,x_0^j]= i \,\theta^{ij}.
\end{equation}
Here the open string mode expansion is
\begin{equation} \label{X-expan}
x^i(\tau,\sigma) =x_0^i + 2\alpha}		\def\da{{\dot\alpha}' (p_0^i \tau -
2\pi \alpha}		\def\da{{\dot\alpha}' (g^{-1} B)^i_j p_0^j \sigma) +
\sqrt{2\alpha}		\def\da{{\dot\alpha}'} \sum_{n\neq 0} \frac{e^{-{\rm i} n\tau}}{ n}
\bigl({\rm i} a^i_n \cos n\sigma -   2\pi \alpha}		\def\da{{\dot\alpha}' (g^{-1} B)^i_j a_n^j \sin
n\sigma \bigr).  \nonumber
\end{equation}
$G^{ij}$ and $\theta}	\def\Th{\Theta}	\def\vth{\vartheta^{ij}$ are the symmetric and
anti-symmetric parts of the  matrix $(g+2\pi \alpha}		\def\da{{\dot\alpha}'B)^{-1}{}^{ij} $,
\begin{equation} \label{Gth}
G^{ij} =  (\frac{1}{g+2\pi \alpha}		\def\da{{\dot\alpha}'B} g \frac{1}{g-2\pi \alpha}		\def\da{{\dot\alpha}'B})^{ij}, \quad
\theta}	\def\Th{\Theta}	\def\vth{\vartheta^{ij}= -(2 \pi \alpha}		\def\da{{\dot\alpha}')^2
(\frac{1}{g+2\pi\alpha}		\def\da{{\dot\alpha}'B} B \frac{1}{g-2\pi \alpha}		\def\da{{\dot\alpha}' B})^{ij}.
\end{equation}
It follows from \eq{cr2} that the  boundary coordinates
$x^i \equiv x^i(\tau,0)$ obey the commutation relation
\begin{equation}\label{boundy-cr}
[x^i,x^j] = i \theta}	\def\Th{\Theta}	\def\vth{\vartheta^{ij}.
\end{equation}
The relation \eq{boundy-cr} implies that the
D-brane worldvolume, where the
opens string endpoints live, is a noncommutative manifold.
One may also starts with the closed string Green function and let
its arguments to approach the boundary to obtain the open string Green
function
\begin{equation} \label{treeG}
\langle x^{i}(\tau)  x^{j}(\tau')  \rangle
= -\alpha}		\def\da{{\dot\alpha}' G^{ij} \ln (\tau-\tau')^2
+ \frac{i}{2} \theta}	\def\Th{\Theta}	\def\vth{\vartheta^{ij} \epsilon(\tau-\tau'),
\end{equation}
where $\epsilon(\tau)$ is the sign of $\tau$.
From \eq{treeG},
Seiberg and Witten \cite{SW} extract the commutator \eq{boundy-cr} again.
$G_{ij} = g_{ij} - (2\pi \alpha}		\def\da{{\dot\alpha}')^2 (Bg^{-1} B)_{ij}$
is called the  open string metric since it
controls the short distance behaviour of open strings.
In contrast, the short distance behaviour for closed strings
is controlled by the closed string metric $g_{ij}$.
One may also treat the boundary $B$-term in \eq{action}
as a perturbation to the open string conformal field theory and
from which one may extract \eq{treeG}
from the modified operator product expansion of the open string vertex
operators \cite{schomerus}.

D-branes in Wess-Zumino-Witten model provides another example of
noncommutative geometry. In this case, the background is not flat since
there is a nonzero $H = dB \sim k^{-1/2}$, where $k$ is the level.
Examining the vertex operator algebra, \cite{ars} obtains that
D-branes are described by nonassociative deformation of fuzzy spheres
with nonassociativity controlled by $1/k$.

\head{String amplitudes and effective action}
The effect of the $B$-field on the open string amplitudes is
simple to determine since only the $x_0^i$ commutation
relation is affected nontrivially.
For example the {\it noncommutative gauge theory} can be
obtained from the tree level string amplitudes readily \cite{ncsym,SW}.
For tree and one loop
\cite{1loop},
we can use
the vertex operator formalism. Generally the vertex operator can
be inserted at either the $\sigma}	\def\S{\Sigma=0$ or $\sigma}	\def\S{\Sigma=\pi$ border, where the string
has the zero mode parts $x_0^i$ and
$y_0^i \equiv x_0^i - (2\pi \alpha}		\def\da{{\dot\alpha}')^2 (g^{-1} B)^i_j p_0^j$
respectively.  The commutation relations are
\begin{equation} \label{xy-cr}
[x_0^i,x_0^j] = i \theta}	\def\Th{\Theta}	\def\vth{\vartheta^{ij},\quad
[x_0^i,y_0^j] =0,\quad [y_0^i,y_0^j] = - i \theta}	\def\Th{\Theta}	\def\vth{\vartheta^{ij}.
\end{equation}
The difference in the commutation relation for $x_0$ and $y_0$
implies that the two borders of the open string has opposite
commutativity. This fact
is not so important for tree level calculations
since one can always choose to put all the interactions at, for
example,  the  $\sigma}	\def\S{\Sigma=0$ border. Collect all these zero mode parts of the
vertex operators, one obtain a phase factor
\begin{equation} \label{phase}
e^{i p^1 x_0} e^{i p^2 x_0} \cdot  e^{i p^N x_0} =
e^{i \sum p^a x_0} e^{ -\frac{i}{2} \sum_{I<J}^N p^I \theta}	\def\Th{\Theta}	\def\vth{\vartheta p^J},
\end{equation}
where the external momenta $p^a$ are ordered cyclically on the circle
and  momentum conservation has been used.
The computation of the oscillator part of  the amplitude is the same
as in the $B=0$ case, except that the metric $G$ is employed in
the contractions.  As a result, the effect of $B$-field on the tree
level string amplitude is simply to
multiply the amplitude at $B=0$ with the  phase factor and
to replace the metric by the metric $G$.
A generic term in the tree level effective action simply becomes
\begin{equation} \label{replace}
\int d^{p+1} x \sqrt{-\det g}\; \mbox{tr} \del^{n_1} \Phi_1  \cdots
\del^{n_k} \Phi_k
\to \int d^{p+1} x \sqrt{-\det G}\; \mbox{tr} \del^{n_1} \Phi_1 * \cdots
 * \del^{n_k} \Phi_k.
\end{equation}
Here the star-product, also called the Moyal product is defined by
\begin{equation}
(f * g) (x) = e^{i \frac{\theta}	\def\Th{\Theta}	\def\vth{\vartheta^{\mu\nu}}{2}
\frac{\del}{\del x_1^\mu} \frac{\del}{\del x_2^\nu}
} f(x_1) g(x_2) |_{x_1=x_2}.
\end{equation}
The star-product is associative,  noncommutative and satisfies
$\overline{f * g} = \bar{g} * \bar{f}$
under complex conjugation. Also for functions vanish rapidly enough at infinity,
it is
\begin{equation} \label{integ}
\int f*g = \int g*f = \int f g.
\end{equation}
An interesting consequence of the nonlocality
as expressed by the noncommutative geometry \eq{boundy-cr}
is the existence of dipole excitation \cite{dipole}
whose extent is proportional to its momentum, $\Delta x = k \theta}	\def\Th{\Theta}	\def\vth{\vartheta$ .
This relation is at the heart of the {\it IR/UV mixing phenomena}
(see below) of noncommutative field theory.
Moyal product in string theory has also appeared earlier in the works
\cite{earlier}.

At  one (and higher) loop level, the
different noncommutativity for the opposite boundaries of open
string becomes essential and give rises to new effects \cite{reggeon}.
In this case non-planar
diagrams require to put vertex operators at the two different
borders $\sigma}	\def\S{\Sigma=0,\pi$. A more complicated phase factor
which involves internal as well as external momentum is resulted.
This leads to the
IR/UV mixing in the noncommutative quantum
field theory. The
different noncommutativity for the opposite boundaries of open
string \eq{xy-cr} is the basic reason  for the  IR/UV
mixing in the noncommutative quantum field theory.
The commutation relations \eq{cr2} are valid at all loops and
therefore one can use them to construct the higher loop
string amplitudes from the first principle \cite{reggeon}. The effect of the
$B$-field on the string interaction can be easily implemented
into the Reggeon vertex and the complete higher loop amplitudes
in B-field have been constructed.

\head{Low energy limit: the Seiberg-Witten limit and the NCOS limit}
The full open string system is still quite complicated.
One may try to decouple the infinite number of massive
string modes to obtain a low energy
field theoretic description by taking the limit $\alpha}		\def\da{{\dot\alpha}' \to 0$.
Since open string are sensitive to $G$ and $\theta}	\def\Th{\Theta}	\def\vth{\vartheta$,
one should take the limit such that $G$ and $\theta}	\def\Th{\Theta}	\def\vth{\vartheta$ are fixed.
For the magnetic case $B_{0i} =0$,
Seiberg and Witten \cite{SW} showed that  this can be achieved with the
following double scaling limit
\begin{equation}
\alpha}		\def\da{{\dot\alpha}' \sim \epsilon^{1/2}, \quad g_{ij} \sim \epsilon \to 0
\end{equation}
with $B_{ij}$ and everything else  kept fixed. Assuming $B$ is of rank
$r$, then \eq{Gth} becomes
\begin{equation} \label{Gth-limit}
G_{ij} = -(2\pi \alpha}		\def\da{{\dot\alpha}')^2 (B g^{-1} B)_{ij},\quad
\theta}	\def\Th{\Theta}	\def\vth{\vartheta^{ij} = (B^{-1})^{ij}, \quad \mbox{for} \;\; i,j = 1,\cdots, r.
\end{equation}
Otherwise $G_{ij} = g_{ij}$, $\theta}	\def\Th{\Theta}	\def\vth{\vartheta^{ij} =0$. One may also argue that
closed string decouples in this limit.
As a result, we obtain  at the low energy limit
a greatly simplified noncommutative Yang-Mills action $F*F$.
See below for more discussion of this field theory.

For the case of a constant  electric field background, say $B_{01}
\neq 0$, there is a critical electric field beyond which open string
become unstable and the theory does not make sense.
Due to the presence of this upper
bound of the electric field, one can show that there is no decoupling
limit where one can reduce the string theory to a field theory on a
noncommutative spacetime.  However one can consider a different
scaling limit where one takes the closed string metric is
scale to infinity appropriately as the electric field approaches the
critical value.  In this limit, all  closed string modes
decoupled. One obtains a novel noncritical string theory
living on a noncommutative spacetime
known as Noncommutative Open String (NCOS). For more details, see
\cite{ncos1,ncos2}

\section{Noncommutative Quantum Field Theory}

Field theory on noncommutative spacetime are defined using the star-product
instead of ordinary product of the fields. To illustrate the general
ideas, let us consider a single real scalar field theory with the action
\begin{equation}
S  = \int d^D x \left[ \frac{1}{2} (\del \phi)^2 - \frac{m^2}{2} \phi^2 -
V(\phi) \right], \quad V(\phi) = \frac{g}{ 4!} \phi^{*4}.
\end{equation}
Due to the property \eq{integ},  free noncommutative field theory is the
same as an ordinary field theory. Treating the interaction term as
perturbation, one can perform the usual quantization and obtain the
Feynman rules: the propagator is unchanged and the interaction vertex in
the momentum space is given by $g$ times the phase factor
\begin{equation} \label{vtx}
 \exp \left(- \frac{i}{ 2} \sum_{1\leq a<b\leq 4} p^{a} \times p^{b}
\right).
\end{equation}
Here $p\times q \equiv p_\mu}	\def\n{\nu \theta}	\def\Th{\Theta}	\def\vth{\vartheta^{\mu}	\def\n{\nu\n} q_\n$. The theory is nonlocal due
to the infinite order of derivatives that appear in the interaction.

\head{Planar and non-planar diagrams} The factor \eq{vtx} is
cyclically symmetric but not permutation symmetric. This is analogous to
the situation of a matrix field theory. Using the same double line
notation as introduced by 't Hooft, one can similarly classify the Feynman
diagrams of noncommutative field theory according to its genus. In
particular the total phase factor of a planar diagram behaves quite
differently from that of a non-planar diagram.
It is easy to
show that a planar diagram will have the phase factor
\begin{equation} \label{planar-V}
V_{\rm p}(p^1, \cdots, p^n) = \exp \left( - \frac{i}{ 2}
\sum_{1\leq a<b\leq n} p^{a} \times p^{b}
\right) ,
\end{equation}
where $p^1, \cdots, p^n$ are the (cyclically ordered)
external momenta of the graph. Note that the phase factor \eq{planar-V} is
independent of the internal momenta. This is not the
case for a non-planar diagram. One can easily show that a non-planar diagram
carries an additional phase factor \cite{filk}
\begin{equation}\label{nonplanar-V}
V_{\rm np} = V_{\rm p} \exp \left(  - \frac{i}{ 2}
\sum_{1\leq  a<b\leq n} C_{ab} p^{a} \times p^{b}
\right),
\end{equation}
where the $C_{ab}$ is the signed intersection matrix of the graph,
whose $ab$ matrix element counts  the number of times the $a$-th
(internal or external) line crosses the $b$-th line. The matrix $C_{ab}$
is not uniquely determined by the diagram as different ways of drawing
the graph could lead to different intersections. However the phase factor
\eq{nonplanar-V} is unique due to momentum conservation.

This different behaviour of the planar and non-planar phase factor has
important consequences.

{\tt 1.} Since the phase factor \eq{planar-V} is independent of the
internal momenta,  the divergences and renormalizability of the
planar diagrams will be (simply) the same as in the commutative theory
and can be handled with standard renormalization techniques.
This is sharply different for the non-planar diagrams. In fact due to the
extra oscillatory internal
momenta dependent phase factor, one can expect the non-planar diagrams
to have an improved ultraviolet (UV) behaviour. It turns out
that planar and non-planar diagrams also differ sharply in their
infrared (IR) behaviour due to
the IR/UV mixing effect.

{\tt 2.} Moreover at  high energies, one can expect
noncommutative field theory will
generically  become planar since the non-planar diagrams will be
suppressed  due to the oscillatory phase factor.

{\tt 3.} In the limit $\theta}	\def\Th{\Theta}	\def\vth{\vartheta\to\infty$,
the non-planar sector will be totally suppressed since the
rapidly oscillating phase factor will cause the non-planar
diagram to vanish upon integrating out the momenta.
Thus generically the large $\theta}	\def\Th{\Theta}	\def\vth{\vartheta$ limit
is analogous to the large $N$ limit where only the
planar diagrams contribute.  However these
expectations do not apply for noncommutative gauge theory since one need to
include {\it open Wilson line} (see below) in the construction of gauge invariant
observables, and the open Wilson line grows in extent with energy and $\theta}	\def\Th{\Theta}	\def\vth{\vartheta$.

\head{IR/UV mixing}
Due to the nonlocal nature of noncommutative field theory, there
is generally  a
mixing of  the UV and IR scales \cite{iruv1}.
The reason is roughly the follow.
Non-planar diagrams generally has phase factors like
$\exp (i k\theta}	\def\Th{\Theta}	\def\vth{\vartheta p)$ , with $k$ a loop momentum, $p$ an external momentum.
Consider
a non-planar diagram which is UV divergent when $\theta}	\def\Th{\Theta}	\def\vth{\vartheta=0$,
one can expect that for very
high loop momenta, the phase factor will oscillate rapidly and
renders the integral finite.  However this is only valid for a
non-vanishing external momentum $\theta}	\def\Th{\Theta}	\def\vth{\vartheta p$, the infinity will come back as
$\theta}	\def\Th{\Theta}	\def\vth{\vartheta p \to 0$. However this time it appears as an IR singularity. Thus
an IR divergence arises
whose origin is from the UV region of the momentum integration and this
is known as the IR/UV mixing phenomena.

To be more specific, consider the $\phi^4$ scalar theory in $D=4$
dimensions.
The one loop self energy has a non-planar contribution given by
\begin{equation} \label{two-point}
\Gamma_{\rm np} = \frac{g}{6 (2\pi)^4} \int \frac{d^4 k}{ k^2 +m^2}
e^{i k\theta}	\def\Th{\Theta}	\def\vth{\vartheta p} \sim \frac{g}{3 (4\pi^2)^{2}} (\L_{\rm eff}^{2} + \cdots),
\end{equation}
where $\L_{\rm eff}^2 = (1/ \L^2 + (\theta}	\def\Th{\Theta}	\def\vth{\vartheta p)^2)^{-1}$.
One can see clearly the IR/UV mixing:
$\Gamma_{\rm np}$ is UV finite as long as $\theta}	\def\Th{\Theta}	\def\vth{\vartheta p \neq 0$;
when $\theta}	\def\Th{\Theta}	\def\vth{\vartheta p =0$, the quadratic UV divergence is recovered,
$\Gamma_{\rm np} \sim \L^{2}$. For supersymmetric theory,
we have at most logarithmic IR
singularities from IR/UV mixing.

IR/UV mixing has a number of interesting consequences.

{\tt 1.} Due to the IR/UV mixing, noncommutative theory does not appear
to have a consistent Wilsonian  description since it will require that
correlation functions computed at finite $\L$
differ from their limiting values by terms of order $1/\L$ for all
values of momenta. However this is not true for theory with IR/UV
mixing. For example, the two point function \eq{two-point} at finite
value of $\L$ differs from its value at $\L =\infty$ by the amount
$ \Gamma_{\rm np}^\L - \Gamma_{\rm np}^{\L = \infty}
\propto 1/(\theta}	\def\Th{\Theta}	\def\vth{\vartheta p)^2$,
for the range of momenta $(\theta}	\def\Th{\Theta}	\def\vth{\vartheta p)^2 \ll 1/\L^2$. It has been
argued that  the IR singularity may be associated with
missing light degrees of freedom in the theory. With new degrees of
freedom appropriately added, one may
recover a conventional Wilsonian description. Moreover it
has been suggested
that to identify these degrees of freedom with the closed string modes
\cite{iruv1}.
However the precise
nature and origin of these degrees of freedom is not  known.

{\tt 2.} The renormalization of the planar diagrams is straight
forward, however it is more subtle for the non-planar diagrams since
the IR/UV-mixed IR singularities may mix with other divergences
at higher loops and render the proof of renormalizability much
more difficult.
IR/UV mixing renders certain large $N$ noncommutative field theory
nonrenormalizable \cite{largeN}.
However for theories with a fixed set of degree of freedoms to start with,
it is believed that one can have sufficiently good control of the IR
divergences and prove renormalizability.
An example of renormalizable noncommutative
quantum field theory is the noncommutative  Wess-Zumino model \cite{wzw}
where IR/UV mixing is absent.
However a general proof is still lacking despite the progress made in
\cite{renorm}.

{\tt 3.} One can show that IR/UV mixing in timelike noncommutative
theory ($\theta}	\def\Th{\Theta}	\def\vth{\vartheta^{0i} \neq 0$) leads to breakdown of perturbative
unitarity \cite{u1,u2,u3}.
For theory without IR/UV mixing, unitarity will be respected even if
the theory has a timelike noncommutativity \cite{u3}. Theory with
lightlike noncommutativity is unitary \cite{u4}.

\section{Noncommutative Gauge Theory}

Gauge theory on noncommutative space is defined by the action
\begin{equation} \label{ncym}
S =-\frac1{4g^2}\,\int d x~\mbox{tr}\Bigl(F_{ij}(x)*  F^{ij}(x)\Bigr) ,
\end{equation}
where the gauge fields $A_i$ are $N\times N$ Hermitian matrices,
$F_{ij}$  is the noncommutative field strength
$ F_{ij}=\partial_i A_j-\partial_j A_i-i [A_i, A_j]_* $
and $\mbox{tr}$ is the ordinary trace over $N\times N$ matrices.
The theory is invariant under the star-gauge transformation
\begin{equation} \label{nct1}
 A_i \to g*A_i*g^\dagger - i g * \del_i g^\dagger,
\end{equation}
where the $N\times N$ matrix function $g(x)$ is unitary with respect
to the star-product $ g* g^\dagger = g^\dagger * g = I$. The solution is
$g =e_*^{i \lambda}	\def\L{\Lambda}$ where $\lambda}	\def\L{\Lambda$ is Hermitian.
In infinitesimal form,
$ \delta}\def\D{\Delta}\def\ddt{\dot\delta_\lambda}	\def\L{\Lambda A_i = \del_i \lambda}	\def\L{\Lambda + i [\lambda}	\def\L{\Lambda, A_i]_*$ .
The noncommutative gauge theory has $N^2$ Hermitian gauge fields.
Because of the star-product, the $U(1)$ sector of the theory is not free
and does not decouple from the $SU(N)$ factor as in the
commutative case.
Note that this way of defining noncommutative gauge theory does not work
for the other Lie group since the star-commutator generally involves
commutator as well as anti-commutator of the Lie algebra, and hence the
expressions above  generally involve the enveloping algebra
of the underlying Lie group. With the help of the
{\it Seiberg-Witten map} (see below),
one can  construct an enveloping algebra valued gauge theory
which has the same number of independent gauge fields and gauge
parameters as the ordinary Lie algebra valued gauge theory \cite{wess}.
However the quantum properties of these theories are much less
understood.
One may also introduce certain automorphism in the
noncommutative $U(N)$ theory
to  restrict the dependence of the
noncommutative space coordinates of the field configurations and obtain a
notion of noncommutative theory with orthogonal and symplectic
star-gauge group \cite{sosp}.  However the theory does not reduce to the
standard gauge theory in the commutative limit $\theta}	\def\Th{\Theta}	\def\vth{\vartheta \to 0$.

\head{Open Wilson line and gauge invariant observables}
One remarkable feature of noncommutative gauge
theory is the mixing of  noncommutative
gauge transformation and spacetime translation, as can be seen from
the following identity
\begin{equation} \label{transl-prop}
e^{i kx} * f(x) * e^{-ikx} = f(x+ k\theta),
\end{equation}
for any function $f$. This is analogous to the situation in general
relativity where translations are also equivalent to
gauge transformations (general
coordinate transformations). Thus as in general relativity,
there are no local gauge invariant
observables in noncommutative gauge theory.
The unification of spacetime and gauge fields in
noncommutative gauge theory can also be seen from the fact that
derivatives can be realized as commutator
$\del_i f \to -i [ \theta}	\def\Th{\Theta}	\def\vth{\vartheta^{-1}_{ij} x^j, f]$
and get absorbed into the vector potential in
the covariant derivative
\begin{equation} \label{cov-D}
D_i  = \del_i + i A_i \to  -i  \theta}	\def\Th{\Theta}	\def\vth{\vartheta^{-1}_{ij} x^j + i A_i.
\end{equation}
Equation \eq{cov-D} clearly demonstrates the unification of spacetime and
gauge fields. Note that the field strength takes the form
$F_{ij} = i [D_i,D_j] + \theta}	\def\Th{\Theta}	\def\vth{\vartheta^{-1}_{ij}$.

The Wilson line operator for a path $C$
running from $x_1$ to $x_2$ is defined by
\begin{equation}
W(C) =
P_* \exp(i \int_{C} A).
\end{equation}
$P_*$ denotes the
path ordering with respect to the star-product, with $A(x_2)$ at
the right. It transforms as
\begin{equation} \label{W-transf}
W(C) \to g(x_1)*W(C)*g(x_2)^\dagger.
\end{equation}
In commutative gauge theory,
the Wilson line operator for closed loop (or its Fourier transform)
is gauge invariant.
In noncommutative gauge theory, the closed Wilson loops are no longer gauge
invariant.  Noncommutative
generalization of the  gauge invariant Wilson loop operator can be
constructed most readily by deforming the  Fourier transform of the
Wilson loop operator.
It turns out that the closed loop has to open in a specific way to
form an open Wilson line in order to be gauge invariant \cite{wilson-line}.
To see this, let us consider a path $C$
connecting points
$x$ and $x +l$. Using \eq{transl-prop}, it is easy to see that
the  operator
\begin{equation} \label{open-w}
\tilde{W}(k) \equiv \int dx\; \mbox{tr} W(C) *  e^{i k x}, \quad
\mbox{with} \quad l^{j}=k_i \theta^{ij},
\end{equation}
is gauge invariant.
Just like Wilson loops in ordinary gauge theory, these operators also
constitute an over complete set of gauge invariant operators
parametrized by the set of curve $C$. When $\theta}	\def\Th{\Theta}	\def\vth{\vartheta=0$, $C$
become a closed loop and we re-obtain the (Fourier transform)
usual closed Wilson loop in commutative gauge theory.
Noncommutative version of the loop equation for closed Wilson loop
has been constructed and involves open Wilson line \cite{loopeqn}.
The open Wilson line is instrumental in the construction of gauge invariant observables
\cite{rey-w1,gross-obs,rey-w2,DW}. An important application  is in the construction
of various couplings of
the noncommutative D-brane to the bulk supergravity fields
\cite{sugra13}. The
equivalence of the commutative and noncommutative couplings to the
RR-fields has leaded to
the exact expression for the Seiberg-Witten map \cite{liu-exact}.
It is remarkable that the one-loop nonplanar effective action for
noncommutative scalar theory \cite{eff-s1}, gauge theory
\cite{eff-g1a,eff-g1b,eff-g1c}
as well as the two-loop effective action for scalar \cite{eff-s2}
can be written compactly in terms of open Wilson line.
Based on this result, the physical origin of the IR/UV mixing has been
elucidated. One may identify the  open Wilson line
with the dipole excitation generically presents
in noncommutative field theory \cite{eff-s1,eff-s2} and hence
explain the presence of the IR/UV mixing.
IR/UV mixing may also be identified with
the instability \cite{eff-g1a,eff-g1b} associated
with the closed string exchange of the noncommutative D-branes.

\head{The Seiberg-Witten map}
The open string is coupled to the one-form $A_i$ living on the
D-brane through the coupling $\int_{\del \S} A$.  For slowly varying fields,
the effective action for this gauge potential can be determined from
the S-matrix and is given by the
Dirac-Born-Infeld (DBI) action. In the presence of $B$-field, the discussion
above \eq{replace} leads to the noncommutative DBI Lagrangian
\begin{equation} \label{DBI1}
L_{NCDBI}(\hat{F}) = G_s^{-1} \mu_p \sqrt{- \det (G + 2\pi \alpha}		\def\da{{\dot\alpha}' \hat{F})} ,
\end{equation}
where $\mu_p = (2\pi)^{-p} (\alpha}		\def\da{{\dot\alpha}')^{-(p+1)/2}$ is the D-brane tension
and $\hat{F}$ is the noncommutative field strength.
However one may also exploit the tensor gauge invariance on the
D-brane (that is, the string sigma model is invariant under
$A \to A- \L, B \to B + d \L$) and consider
the combination $F+B$ as a whole. In this case it is like having the
open string coupled to  the boundary gauge field strength $F+B$ and
there is no $B$ field. And we have the usual DBI Lagrangian \cite{DBI12}
\begin{equation} \label{DBI2}
L_{DBI}(F) = g_s^{-1} \mu_p  \sqrt{- \det (G + 2\pi \alpha}		\def\da{{\dot\alpha}' (F+B))} .
\end{equation}
In \eq{DBI1} and \eq{DBI2}, $G_s$ and $g_s$ are the effective open
string couplings in the noncommutative and commutative descriptions.
Although looks quite different, Seiberg and
Witten showed the commutative and noncommutative DBI actions
are indeed equivalent if the open string couplings are related by
$g_s =G_s \sqrt{\det (g+ 2\pi \alpha}		\def\da{{\dot\alpha}' B)/\det G} $
and there is a field redefinition that relate the
commutative and noncommutative gauge fields. The map
$\hat{A} = \hat{A} (A)$ is called the Seiberg-Witten map \cite{SW}.
Moreover, the noncommutative gauge symmetry is equivalent to the
ordinary gauge symmetry in the  sense that they have the same set of
orbits under gauge transformation:
\begin{equation}
\label{swmap-def}
\hat A(A) + \hat\delta_{\hat\lambda}	\def\L{\Lambda} \hat A(A) =
\hat A(A + \delta_\lambda}	\def\L{\Lambda A) .
\end{equation}
Here $\hat A_i$ and  $\hat\lambda}	\def\L{\Lambda$ are the  noncommutative gauge field and
noncommutative gauge transformation parameter,
$A_i$ and  $\lambda}	\def\L{\Lambda$ are the  ordinary gauge field and  ordinary
transformation parameter.
The map between $\hat A_i$ and $ A_i$ is called the Seiberg-Witten map.
\eq{swmap-def} can be solved only if the transformation parameter
$\hat\lambda}	\def\L{\Lambda = \hat \lambda}	\def\L{\Lambda (\lambda}	\def\L{\Lambda, A)$ is field dependent.
The Seiberg-Witten map is characterized by the Seiberg-Witten
differential equation,
\begin{equation}
\delta \hat A_i(\theta ) = -\frac{1}{4}\delta\theta^{kl} \big[\hat A_k*
(\partial_l \hat A_i + \hat F_{li}) + (\partial_l \hat A_i +\hat
F_{li})* \hat A_k \big] .
\end{equation}
An  exact solution for the Seiberg-Witten map can be written down with
the help of the  open Wilson line.
For the case of $U(1)$  with constant $F$, we have the exact
solution
$ \hat{F} = (1+ F \theta}	\def\Th{\Theta}	\def\vth{\vartheta)^{-1} F$.

That there is a field redefinition that allows one to write the
effective action in terms of different fields with different gauge
symmetries may seems puzzling in the first instant. However it has a
clear physical origin in terms of the string worldsheet. In fact there
is different possible schemes to regularize the short distance
divergence on the worldsheet. One can show that the Pauli-Villar
regularization gives the commutative description, while the point
splitting regularization gives the noncommutative description. Since
theories defined by different regularization schemes are related by a
coupling constant redefinition, this implies the commutative and
noncommutative description are related by a field redefinition because
the couplings on the worldsheet are just the spacetime fields.

Despite this formal equivalence, the physics of the noncommutative
theories is generally quite different from the commutative one.
First it is clear that generally the Seiberg-Witten map may
take nonsingular configurations to singular configurations.
Second, the observables one is interested in are also generally different.
Moreover the two descriptions are generally good for different regimes:
the conventional gauge theory description is simpler for small $B$ and
noncommutative  description is simpler for large $B$.

\head{Perturbative gauge theory dynamics}
The noncommutative gauge symmetry \eq{nct1}
can be fixed as usual by employing the
Fadeev-Popov procedure, resulting in Feynman rules that are similar to
the conventional gauge theory. The important difference is that
now we have to
amend to the structure constant the phase factors
\eq{planar-V} and \eq{nonplanar-V}.
It turns out that the non-planar
$U(N)$ diagrams contribute (only) to the $U(1)$ part of the theory. As a
result, unlike the commutative case, the $U(1)$ part of the theory
is no longer decoupled and free \cite{armoni}.
Noncommutative gauge theory is one-loop renormalizable \cite{renorm-gauge,renorm-gaugeN}.
The beta-function is determined
solely by the planar diagrams and, at one loop, is given by
\cite{renorm-gauge,renorm-gaugeN,iruv2}
\begin{equation}
\beta(g) = -\frac{22}{ 3} \frac{N g^3}{16 \pi^2}, \quad
\mbox{for $N \geq 1$}.
\end{equation}
Note that the beta function is independent of $\theta}	\def\Th{\Theta}	\def\vth{\vartheta$,
the noncommutative $U(1)$ is asymptotically free and
does not reduce to the commutative theory when $\theta}	\def\Th{\Theta}	\def\vth{\vartheta \to 0$.
Noncommutative theory beyond  the tree level
is generally not smooth in the limit $\theta}	\def\Th{\Theta}	\def\vth{\vartheta \to 0$.
Discontinuity of this kind was also noted for the Chern-Simon system
\cite{CS}.

Gauge anomalies can be similarly discussed \cite{anom1,anom2,anom3} and satisfy the
noncommutative generalizations of the Wess-Zumino consistency
conditions \cite{anom3}. In $d=2n$ dimensions, the anomaly involves the combination
$\mbox{tr} (T^{a_1} T^{a_2} \cdots T^{a_{n+1}})$ rather than the usual symmetrized trace
since the phase factor is
not permutation symmetric. As a result, the usual
cancellation of anomaly does not work and is the main obstacle to the
construction of noncommutative chiral gauge theory.

There is a number of interesting features to mention for the
IR/UV mixing \cite{iruv2,iruv3}  in noncommutative gauge theory:
{\tt 1.} IR/UV mixing generically yields pole like  IR
singularities. Despite the appearance of IR poles,
gauge invariance of the theory is not endangered \cite{iruv3}.
{\tt 2.} One can show that only the $U(1)$ sector is affected
by IR/UV mixing.
{\tt 3.} As a result of IR/UV mixing,  noncommutative $U(1)$ photons
polarized in the noncommutative
plane will have different dispersion relations from those which are not \cite{iruv3}.
Strange as it is, this is consistent with gauge invariance.

\section{Noncommutative Solitons, Instantons and D-branes}

Solitons and instantons play important roles in the nonperturbative
aspects of field theory. The nonlocality of star-product gives noncommutative
field theory a stringy nature.
It is remarkable that this applies to the nonperturbative sector as well.
Solitons and instantons in the noncommutative gauge theory
reproduce amazingly the properties of D-brane in the string. The reviews
\cite{trieste, harvey} are recommended.

\head{GMS solitons}
Derrick theorem says that commutative scalar field theories in
two or higher dimensions
do not admit any finite energy classical solution. This follows from a
simple scaling argument, which will fail when the theory becomes
noncommutative
since noncommutativity introduce a fixed length scale $\sqrt{\theta}	\def\Th{\Theta}	\def\vth{\vartheta}$.
Noncommutative solitons in pure scalar theory can be easily constructed
at the limit $\theta}	\def\Th{\Theta}	\def\vth{\vartheta = \infty$. For example, consider a (2+1)-dimensional
single scalar theory with a potential $V$ and noncommutativity
$\theta}	\def\Th{\Theta}	\def\vth{\vartheta^{12} =\theta}	\def\Th{\Theta}	\def\vth{\vartheta$. In the limit $\theta}	\def\Th{\Theta}	\def\vth{\vartheta = \infty$,
the potential term dominates and
the noncommutative solitons are determined by the equation
\begin{equation} \label{Vs}
\del V / \del \phi =0.
\end{equation}
Equation \eq{Vs} can be easily
solved in terms of projector. Assuming $V$ has no linear term,
the general soliton (up to unitary equivalence) is
\begin{equation}\label{nc-soliton}
\phi = \sum_i \lambda}	\def\L{\Lambda_i P_i,
\end{equation}
where $\lambda}	\def\L{\Lambda_i$ are the roots of $V'(\lambda}	\def\L{\Lambda) =0$ and
$P_i$ is a set of orthogonal projectors. For
real scalar field theory, we have to restrict the sum to real roots only.
These solutions are known as the Gopakumar-Minwalla-Strominger (GMS)
solitons \cite{gms}.
A simple example of projector is  given by $P =  \ket{0}\bra{0}$,
which corresponds to a Gaussian profile in the $x^1, x^2$ plane with width
$\sqrt{\theta}	\def\Th{\Theta}	\def\vth{\vartheta}$. The soliton continues to exist until $\theta}	\def\Th{\Theta}	\def\vth{\vartheta$ decreases below a
certain critical $\theta}	\def\Th{\Theta}	\def\vth{\vartheta_c$.

New solution can be generated from known one using the so called
solution generating technique.
If $\phi$ is a solution of \eq{Vs}, then
\begin{equation}
\phi' = T^\dagger \phi T
\end{equation}
is also a solution provided that $T T^\dagger =1$.
In an infinite dimensional Hilbert space, $T$ is not necessary to be
unitary, i.e. $T^\dagger T \neq 1$.
In this case, $T$ is said to be a partial isometry. The
new solution $\phi'$ is different from $\phi$ since they are
not related by  global transformation of basis.

\head{Tachyon condensation and D-branes}
A beautiful application of the noncommutative soliton is in the
construction of D-brane as solitons of the tachyon field in
noncommutative open string theory
\cite{soliton-d}
For the bosonic string theory, one may consider it a space filling
D25-brane. Integrating out the massive string modes lead to an effective
action for the tachyon and the massless gauge field $A_\mu}	\def\n{\nu$.
We remark that different from the pure scalar case,
noncommutative soliton can be constructed exactly for finite $\theta}	\def\Th{\Theta}	\def\vth{\vartheta$ in a
system with gauge and scalar fields \cite{ncsol-exact}.
Although the detailed form of the effective action is unknown,
one has enough confidence to say what the true vacuum configuration is
according to the Sen conjecture. See for example, \cite{TZ-rev}
for excellent review
on this subject. One can then apply the
solution generating technique to generate new soliton solution.
With a $B$-field of rank $2k$, one can construct this way solutions which are
localized in $\mathbb{R}^{2k}$ and represents a D$(25-2k)$-brane. This is
supported by the  matching of the tension and the spectrum of
fluctuation around the soliton configuration.
Similar ideas can also be applied to construct D-branes in type II
string theory. Again the starting point is an unstable brane configuration
with tachyon field(s). There are two types of unstable D-branes:
non-BPS D$p$-branes ($p$ odd in IIA theory and $p$
even in IIB theory) and
BPS branes anti-branes D$p$-$\overline{{\rm D}p}$ system.
A similar analysis
allows one to identify the noncommutative soliton with the
lower dimensional BPS D-branes which arises from tachyon condensation.

One main motivation for studying tachyon condensation in open string
theory is the hope that open string theory may provide a fundamental
nonperturbative formulation of string theory. It may not be too
surprising that D-branes can be obtained in terms of open string fields.
However to describe closed string and NS-branes in terms of open string
degree of freedom remain an obstacle.

\head{Noncommutative instanton and monopoles}
Instantons on noncommutative $\bf{R}_\theta}	\def\Th{\Theta}	\def\vth{\vartheta^4$ can be constructed readily
using the ADHM formalism by  modifying the
ADHM constraints with a constant additive term \cite{ns-ins}.
The result is that
the self-dual (resp. anti-self-dual) instanton moduli space depends only on the
anti-self-dual (resp. self-dual) part.
The construction go through even in the $U(1)$ case. Consider a self-dual
$\theta}	\def\Th{\Theta}	\def\vth{\vartheta$, the ADHM constraints for the
self-dual instanton is the
same as in the commutative case, and there is no  nonsingular
solution. On the other hand, the ADHM constraints for the
anti-self-dual instanton get modified and admit nontrivial solution. This
noncommutative  instanton solution is nonsingular with size
$\sqrt{\theta}	\def\Th{\Theta}	\def\vth{\vartheta}$.  Although ADHM method does not
give a self-dual instanton, a direct construction can be applied to
obtain  non ADHM self-dual instantons. Recall that the
gauge field strength can be written as
$F_{ij} = i [D_i,D_j] + \theta}	\def\Th{\Theta}	\def\vth{\vartheta^{-1}_{ij}$,
where $D_i$ is given by the function on the right hand side of \eq{cov-D}.
Thus a simple self-dual solution can be constructed with
\begin{equation}
D_i =  i \theta}	\def\Th{\Theta}	\def\vth{\vartheta^{-1}_{ij} T^\dagger x^j T ,
\end{equation}
where $T$ is a partial isometry which satisfies $T T^\dagger =1$, but
$T^\dagger T =1 -P$ is not necessarily the identity. It is clear
that $P$ is a projector. The field strength
\begin{equation}
F_{ij} = \theta}	\def\Th{\Theta}	\def\vth{\vartheta^{-1}_{ij} P
\end{equation}
is self-dual and has an instanton number $n$ where $n$ is the rank of
the projector.
The noncommutative instanton represent a D$(p-4)$-brane within a D$p$-brane.
The ADHM constraints are just the D-flatness condition for
the D-brane worldvolume  gauge theory.
The additive constant to the ADHM constraints also has a simple
interpretation as a Fayet-Illiopolous parameter which appears
in the presence of $B$-field.

On noncommutative $\mathbb{R}^3$  (say $\theta}	\def\Th{\Theta}	\def\vth{\vartheta^{12}= \theta}	\def\Th{\Theta}	\def\vth{\vartheta$),
BPS monopoles satisfy the Bogomolny equation \cite{mono}
\begin{equation}
\nabla_i \Phi = \pm B_i, \quad i =1,2,3
\end{equation}
and can be obtained by solving the Nahm equation
\begin{equation}
\del_z T_i = \epsilon_{ijk} T_j T_k + \delta}\def\D{\Delta}\def\ddt{\dot\delta_{i3} \theta}	\def\Th{\Theta}	\def\vth{\vartheta.
\end{equation}
$T_i$ are
$k\times k$ Hermitian matrices depending on an auxiliary variable
$z$ and  $k$ gives the charge of the monopole.
Noncommutativity modifies the Nahm equation
with a constant term, which can be absorbed by a constant
shift of the generators. Therefore unlike the case of instanton, the
monopole moduli space is not modified by noncommutative deformation.
The Nahm construction has clear physical meaning in string theory.
The monopole (electric charge)
can be interpreted as a D-string (fundamental string) ending on a D3-brane.
One can also suspend $k$ D-string between a collection of $N$ parallel
D3-branes, this would correspond to a charge $k$ monopole in a
Higgsed $U(N)$ gauge theory. The matrices $X^i$ correspond to the
matrix transverse coordinates of the D-strings which lie within the
D3-branes.

\section{ Further Topics}

Finally we include a brief discussions of some further topics of
interests.

\noindent{\sf 1.} The  noncommutative geometry we discuss here is
of canonical type. Other deformations exists, for example,
kappa-deformation \cite{kappa} and fuzzy sphere which are of the Lie-algebra type,
quantum group deformation \cite{QG} which is a quadratic type deformation:
$ x^i x^j = q^{-1} \hat{R}^{ij}_{kl} x^k x^l$, whose
consistency is guaranteed by the Yang-Baxter equation. It is
interesting to see whether these noncommutative geometries arise from
string theory. Another natural generalization is to consider
noncommutative geometry of superspace. A simple example is to consider
the fermionic coordinates to be deformed with the nonvanishing relation
\begin{equation} \label{thth}
\{\theta}	\def\Th{\Theta}	\def\vth{\vartheta^\alpha}		\def\da{{\dot\alpha}, \theta}	\def\Th{\Theta}	\def\vth{\vartheta^\beta}		\def\db{{\dot\beta}\} = C^{\alpha}		\def\da{{\dot\alpha}\beta}		\def\db{{\dot\beta}},
\end{equation}
where $C^{\alpha}		\def\da{{\dot\alpha} \beta}		\def\db{{\dot\beta}}$ are constants. It has been shown that \eq{thth}
arises in certain Calabi-Yau compactification of type IIB string theory
in the presence of RR-background \cite{gp13}.
The deformation \eq{thth} reduces the number of
supersymmetries to half. Therefore it is called $\cN =1/2$ supersymmetry
\cite{seiberg-ncsusy}.
The noncommutativity \eq{thth} can be implemented  on the
superspace $(y^i, \theta}	\def\Th{\Theta}	\def\vth{\vartheta^\alpha}		\def\da{{\dot\alpha}, \bar{\theta}	\def\Th{\Theta}	\def\vth{\vartheta}^{\dot{\alpha}		\def\da{{\dot\alpha}}})$ as a star-product
for the $\theta}	\def\Th{\Theta}	\def\vth{\vartheta^\alpha}		\def\da{{\dot\alpha}$'s. Unlike the bosonic
deformation which involves an infinite number of higher derivatives,
the star-product for \eq{thth} stops at order $C^2$ due
to the Grassmanian nature of the fermionic  coordinates.
Field theory with $\cN=1/2$ supersymmetry is local and differs
from the ordinary $\cN=1$ theory by only a
few number of  supersymmetry breaking terms.
The $N=1/2$ WZ model is renormalizable \cite{ncsusy-wz} if
extra $F$ and $F^3$ terms are added to the original Lagrangian, where
$F$ is the auxiliary field.
The $N=1/2$ gauge theory is also renormalizable \cite{ncsusy-g}.

\noindent{\sf 2.} Integrability of a theory provides valuable
information beyond the perturbative level.  An integrable field theory
is characterized by an infinite number of conserved charges in involution.
It is natural to ask whether integrability is
preserved by noncommutative deformation.
Integrable noncommutative integrable field theories
have  been constructed, see \cite{int-field}.
In the commutative case, Ward \cite{ward} has conjectured that all (1+1) and
(2+1)-dimensional integrable system can be obtained from the
4-dimensional self-dual Yang-Mills equation by reduction.
Validity of the noncommutative version of the Ward conjecture
has been confirmed so far \cite{int-field}, \cite{lax}.
It is interesting to see whether it is true in general.

\noindent{\sf 3.} Locality and Lorentz symmetry form the corner stones
of quantum field theory and standard model physics of particles.
Noncommutative field theory
provides a theoretical framework where one can discuss about effects of
nonlocality and Lorentz symmetry violation. Possible phenomenological
signals \cite{phen} have been investigated (mostly at the tree
level) and bound has been placed on the extent of noncommutativity.
Proper understanding and a better control of the IR/UV mixing remains
the crux of the problem. Noncommutative geometry may also be relevant for
cosmology and inflation \cite{cosmo}.

\noindent{\sf 4.} Like the standard AdS/CFT correspondence \cite{adscft}, the
noncommutative gauge theory should also has a gravity dual description
\cite{ncadscft,ncadscft2}. The
supergravity background can be determined by considering the
decoupling limit of D-branes with a NS B-field background.
However since the noncommutative gauge theory does not permit
any conventional local gauge invariant observable, the
usual AdS/CFT correspondence that relates field theory correlators with
bulk interaction does not seem to apply.
It has been argued that \cite{rey-w2} generic properties like the
dipole relation between length and momentum for open Wilson line can be seen
from the gravity side. A more precise understanding of the duality
map is called for.

redpajama_set_name: RedPajamaArXiv


text:
Interactions among biological control, cultural control and barley resistance to the Russian wheat aphid, Diuraphis noxia (Kurdjumov), in Colorado, Kansas and Nebraska
Sotelo-Cardona, Paola Andrea
The Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Hemiptera: Aphididae) (RWA), is an important pest in the U.S. Western Plains, causing hundreds of millions of dollars of losses to wheat and barley production through reduced yields and insecticide application costs. The objectives of this research were to evaluate the performance of two RWA-resistant barley varieties planted approximately one month earlier than normal in experimental fields at Fort Collins, Colorado; Tribune, Kansas; and Sidney, Nebraska during 2007, 2008, and 2009. The experimental design was a split-plot design with two main plot treatments (early and normal planting dates), and four split plot treatments (barley varieties) that were randomized within each main treatment plot. The varieties included two RWA-barley resistant varieties, Sidney and Stoneham, and the susceptible variety, Otis, under thiamethoxam-protected and unprotected regimes. Sampling of RWA, other cereal aphids, and natural enemy populations was conducted on four dates from mid May through early July. RWA populations collected from early-planted plots (first week of March) were significantly lower than normal-planted plots in 2007-2009 at the Fort Collins, Colorado and Tribune, Kansas sites. In samples collected from early planting date plots, RWA-resistant varieties yielded RWA populations similar to those found on the insecticide-treated susceptible variety at both Fort Collins and Tribune. At the Sidney, Nebraska site, very low RWA populations were present and there were no differences between either planting date or varietal treatments. The combined effect of early planting and RWA-resistant varieties reduced RWA populations at the Fort Collins, Colorado site in all three years. Results were similar at the Tribune, Kansas site in 2007, but differences due to planting date or variety were not observed in 2008 or 2009. The lowest RWA populations occurred at the Sidney, Nebraska site, were independent of planting date and varietal treatments. The RWA-resistant barley varieties had no negative impact on populations of other cereal aphids compared to those found on the susceptible variety, Otis at any of the three research sites. The only treatment effective in reducing other cereal aphids was the insecticide, thiamethoxam. There was also no clear response of populations of other cereal aphids to different planting date. Neither the RWA-resistant barley varieties nor the systemic, short residual action insecticide treatment had adverse affects on the abundance of natural enemies.
Keywords: Host plant resistance; Biological control; Cultural control; Integrated pest management; Russian wheat aphid; Barley
Department: Department of Entomology
Major Professor: C. Michael Smith
Filename: PaolaSotelo2010.pdf

redpajama_set_name: RedPajamaCommonCrawl


The Barco Alchemy DP2K-19B is a bright and fully integrated digital cinema projector for theaters with screens up to 19m (62ft) wide, based on Texas Instruments' 1.2" DLP Cinema® chip. It ensures exceptional image quality for a premium movie experience in 2D and 3D. By merging the projector and media server functionalities into one projector module, the Barco Alchemy DP2K-19B is a full-fledged, DCI-compliant projector and media-server solution with on-board storage. Reducing the required hardware, it increases simplicity and reliability. The smart projector even detects potential operational errors and warns users in case of mishaps. Great in TMS environments, it operates stand-alone in single-screen applications. Thanks to the embedded Barco Web Commander user interface, shows can be created and scheduled remotely.
Geared with the integrated Barco Alchemy technology that drives operational and maintenance costs down, the DP2K-19B offers superior image processing, pristine images and ultimate reliability at a low TCO.
The DP2K-19B projector is also available in a package with a third-party media server and it can be ordered without the Barco Alchemy module as well.


MILAN – It is the first public declaration since Yara disappeared. "Give us our daughter back", begged Yara Gambirasio's parents in a press appeal some 36 days after the disappearance of the girl from Brembate Sopra in the province of Bergamo.
"WE BEG COMPASSION" – "We beg the compassion of the people who have taken Yara", said Fulvio and Maura Gambirasio, holding hands. "We ask them to find some spark of love in their conscience, look her in the eyes and open the door or gate that separates her from her freedom". Speaking at the former sunlight therapy centre that was investigators' base of operations until a few days ago, Yara's parents said: "We beseech you to give us our daughter back. Help us to piece our daily lives back together again. Help us to rebuild our normality".
FULL TEXT – Here is the full text of the appeal: "We are a simple family, a household whose unity is based on love, respect, sincerity and the glow of our peaceful existence. For the past month, we have been asking ourselves endless questions about who, what, how, when and why all this is happening to us. We are not looking for answers. We do not seek to know. We are not tormenting ourselves trying to understand. We are not pointing the finger at anyone. We just want, immensely, for our daughter to return to her world, to her village, to her home, to the embrace of those who love her. We beg the compassion of the people who have taken Yara. We ask them to find some spark of love in their conscience, look her in the eyes and open the door or gate that separates her from her freedom. We beseech you to give us our daughter back. Help us to piece our daily lives back together again. Help us to rebuild our normality. People know us. We have never done or wished ill on anyone. We have always shown we are an open, transparent family, ready to help others. We do not deserve to continue our life without Yara's smile. Thank you".
"WE ARE CONVINCED SHE IS ALIVE" – Yara's parents also thanked "everyone who with such love and respect is supporting us on this journey of hope". Before reading the appeal, the Gambirasios explained to journalists that they used the term "journey of hope" because "we believe, we are convinced, as are the police, that Yara is alive".


text:
Most Americans Admit to Driving While Drowsy: Poll
WEDNESDAY, Nov. 2, 2022 (HealthDay News) -- Most people consider drowsy driving dangerous, but an estimated 37 million Americans still get behind the wheel at least once a year when they're so tired they can barely keep their eyes open.
About six in 10 people admitted to drowsy driving in a new survey by the National Sleep Foundation (NSF).
"Drowsy driving is impaired driving," said Joseph Dzierzewski, the foundation's vice president of research and scientific affairs. "We see that while most Americans believe drowsy driving is risky, they still drive when not fully alert. The good news is — drowsy driving is preventable."
In a survey conducted this fall, nearly 20% of respondents were overly confident in their ability to drive after sleeping two hours or less the previous night.
Respondents who said they get the recommended amount of sleep — about seven to nine hours per night for adults and eight to 10 for teens — were less likely to drive drowsy.
Members of historically excluded groups were at higher risk for drowsy driving, according to the NSF, which said it may be an issue of sleep health equity. (In a position statement issued earlier this year, the foundation noted that people of color in the United States are disproportionately affected by poor sleep health and sleep disorders.)
An estimated 6,400 people die in the United States each year because of car crashes linked to drowsy driving, according to the NSF.
"At NSF, we are dedicated to helping everyone prioritize their sleep," CEO John Lopos said in a foundation news release. "As we mark the 15th anniversary of Drowsy Driving Prevention Week, we hope to educate the public on the importance of getting the sleep they need and reduce the number of drivers who choose to get behind the wheel while sleep deprived."
If you aren't getting enough sleep to be your "best-slept self," you may be unfit to operate a motor vehicle, Lopos added.
The foundation said drivers should plan to take a companion on long trips to help look for signs of drowsiness and help driving when needed. A good driving companion stays awake to talk to the driver, the NSF said.
Take regular stops, the experts urged, about every 100 miles or two hours.
The foundation noted you may be drowsy if you're frequently blinking, yawning or having difficulty with lane and speed control.
The U.S. Department of Transportation has more on safe driving.
SOURCE: National Sleep Foundation, news release, Nov. 2, 2022
A Vocabulary for Sleep
Transient Tachypnea of the Newborn
For Adults: To Nap or Not to Nap?
Sleep: Test Your Knowledge


text:
Claremont killer trial LIVE: Court begins to hear of international journey Ciara's hair exhibits took
Claremont killer trial
By Heather McNeill
Updated January 15, 2020 — 7.47pm first published at 11.49am
7.47pm on Jan 15, 2020
A breakdown of journey of Ciara's critical hair exhibits
As the state moves into quite technical evidence involving the movements of Ciara's hair mass, WAtoday has created a table to breakdown the four critical exhibits that form part of the prosecution's case in relation to its fibre evidence.
Judge releases 1997 image of Claremont at night
A photo taken by Mr Hyde in April 1997 showing the amount of lighting on Stirling Highway, Claremont around the same time of night that Ciara vanished from the area.
Court has wrapped up for the day
Court has adjourned for the day.
Mr Hyde will resume his evidence tomorrow from 10am.
Justice Stephen Hall has agreed to publicly release a photo taken of Stirling Highway in Claremont around midnight which shows the lighting in the area at the time.
The photo will be placed on this blog once made available.
Forensic journey of Ciara's critical hair samples beginning to be revealed
Mr Hyde is now being shown entries he made into his police diary on February 5, 1999 which shows he collected a sample of Ciara's hair mass and from the Path Centre for transfer to the FBI in the U.S.
The notation said he collected the hair mass and a DNA sample of 'Williams' from now disgraced Pathwest DNA analyst Laurie Webb.
At the time, public servant Lance Williams was a suspect in the Claremont killings, and had the year prior, voluntarily submitted his DNA for testing.
On July 18, 2005, he said he opened three boxes which contained Ciara's hair samples for the purpose of doing a stocktake on the items inside which he said included samples, some in in yellow top containers, and all in plastic bags.
"I don't have any recollection of this day, only what's being indicated to me as part of a running sheet ... which makes reference to me doing this," he said.
Mr Hyde said he opened the boxes, viewed the contents inside, and then closed and re-sealed them.
He said he opened the boxes again a week later on July 26, 2005.
The state is relying on four critical exhibits taken from samples of Ciara's hair from which it alleges fibres linked to Mr Edwards were found.
One of the exhibits is known as K1 - which was examined by the FBI in 1999, and an examination of that petri dish in late 2012 allegedly found one blue polyester fibre.
The remaining critical hair exhibits, RH17, and VW1 and VW1A (taken from AJM54) were tested in 2018-2019, after Mr Edwards' arrest.
Mr Hyde is being shown exhibit VW1 in a sealed plastic bag - it was in one of the boxes he opened in 2005.
He said also in the same box were two empty plastic bags - one marked K1, and the other 'K.Glennon hair mass'.
"They'd been removed from the bag which had VW1 - the hair mass - in a bag sealed, and these were loose bags also in the [larger] bag within the box," he said.
So he is saying one of the boxes he examined had a large plastic bag in it, with one smaller sealed bag inside (VW1) and two loose, empty bags.
In another of the boxes he opened was critical exhibit VW1A, a sub-sample of VW1 which was in what appeared to be a yellow-sealed envelope inside a sealed plastic bag.
When asked again what his involvement with the exhibits were he has said, "The only purpose of what we were doing was detailing what was in the boxes".
Court hears details of post-mortem on Ciara's body
Ms Barbagallo has now moved onto the day the post-mortem on Ciara's body was conducted, April 4, 1997.
Mr Hyde said he was present at the examination and took 72 photographs of the body.
He said he would have wore a white mortuary coverall, gloves and either boot covers or wellington boots, as well as a surgical mask.
"I looked through the video and as a photographer, apart from being close to the body to take photographs, I would have had no reason to touch the body," he said.
The post-mortem was recorded.
Mr Hyde also recalled attending the mortuary again to take photos during a second examination by forensic pathologist, Karin Margolius.
He took seven photos that day, including of her hands, and wore similar protective clothing as during the post-mortem.
Officer being asked about critical hair exhibit
Ms Barbagallo is asking Mr Hyde about one of the state's critical exhibits, RH17 - a sample taken from Ciara's hair while she was in situ.
The state alleges two blue polyester fibres were found in the sample.
The taking of the exhibit was recorded on the running sheet, but not captured on film due to a three-minute break in recording.
Ms Barbagallo: Do you have any independent recollection of where that might have come from?
Mr Hyde: No, sorry.
He is now going through his running sheet which shows around 20 officers were involved or watching the examination of Ciara's body in situ.
It shows the critical exhibit RH17 was collected at 3.07pm and taken to the forensic fridge, situated at the site on a trailer, at 3.11pm by forensic officer Adam McCulloch.
Mr Hyde said the exhibit would have then been taken to police headquarters, and although he cannot recall, he said it likely would have been placed in an exhibit fridge as it was considered biological matter.
Forensic officer wore Yakka-made blue overalls to Ciara's crime scene
Telstra-issued work trousers from around the 1990s period. State prosecutors argue the fibres pulled from tape lifts by forensics officers match the same brand of pants.
Ms Barbagallo has now moved onto Mr Hyde's involvement in the forensic examination of Ciara's crime scene on April 3, 1997.
He said he was first tasked to go up in the police helicopter to take aerial photographs of the scene before then being appointed the scribe during the examination of Ciara's body in situ.
"My function was to continue adding to the running sheet as other officers indicated to me something needed recording ... or to add to the exhibit list.
He said he was wearing police-issued boots and light blue Yakka overalls.
The state alleges the blue polyester fibres found on Ciara match the custom-made navy Telstra trousers manufactured by Yakka for Telstra employees.
Mr Hyde said he could not recall if he was wearing gloves.
"I may have been, I may not have been because I wasn't in contact with anything,"he said.
"I would think my [closest] distance [to the body] would be no closer than two metres, 1.5 metres - close but not right on the body."
Forensic officer sent to Stirling Highway at midnight to take photos after Ciara's death
Mr Hyde has resumed giving his evidence.
Ms Barbagallo has moved onto April 20, 1997, when Mr Hyde attended Stirling Highway and Bay View Terrace in Claremont to capture the lighting in the area at a particular time, prior to midnight.
Ciara had disappeared from the area around midnight five week's prior.
The images are being shown on the court screens.
"It's total darkness, the only lighting is from street lighting and motor vehicles coming through," he said.
Court is breaking for lunch
Court has adjourned until 2pm. When it resumes, Mr Hyde will continue to give his evidence.
Court resumes after technical glitch
Court has resumed after an unexpected two-hour adjournment to rectify an audio issue impacting the court's transcribing service.
Ms Barbagallo is asking if Mr Hyde recalled whether the exhibits from Jane's unit were logged on the property tracing system.
He said he could not recall what happened to the exhibits after they were collected, but that it was procedure to take exhibits to the exhibits storage area at police headquarters and enter them into the property tracing system.
He is now being asked about the seizure of Jane's hairbrush, which was written on the exhibit list as 'RSK 14 - medications, hairbrush - bathroom cabinet'.
The court has previously heard this exhibit item at some stage in the electronic entering of the transfer of the exhibits, changed to 'RKS 13 - hairbrush'.
Forensic supervisor Robert Hemelaar said during his evidence this was likely a mistake.
It is not yet clear why this exhibit is relevant.
Most Viewed in National


text:
This topic describes how to build and run Go from source code.
To install with an installer, see Download and install.

Introduction

Go is an open source project, distributed under a
BSD-style license.
This document explains how to check out the sources,
build them on your own machine, and run them.

Most users don't need to do this, and will instead install
from precompiled binary packages as described in
Download and install,
a much simpler process.
If you want to help develop what goes into those precompiled
packages, though, read on.

There are two official Go compiler toolchains.
This document focuses on the gc Go
compiler and tools.
For information on how to work on gccgo, a more traditional
compiler using the GCC back end, see
Setting up and using gccgo.

The Go compilers support the following instruction sets:

  amd64, 386

  The x86 instruction set, 64- and 32-bit.

  arm64, arm

  The ARM instruction set, 64-bit (AArch64) and 32-bit.

  loong64

  The 64-bit LoongArch instruction set.

  mips64, mips64le, mips,  mipsle

  The MIPS instruction set, big- and little-endian, 64- and 32-bit.

  ppc64, ppc64le

  The 64-bit PowerPC instruction set, big- and little-endian.

  riscv64

  The 64-bit RISC-V instruction set.

  s390x

  The IBM z/Architecture.

  wasm

  WebAssembly.

The compilers can target the AIX, Android, DragonFly BSD, FreeBSD,
Illumos, Linux, macOS/iOS (Darwin), NetBSD, OpenBSD, Plan 9, Solaris,
and Windows operating systems (although not all operating systems
support all architectures).

A list of ports which are considered "first class" is available at the
first class ports
wiki page.

The full set of supported combinations is listed in the
discussion of environment variables below.

See the main installation page for the overall system requirements.
The following additional constraints apply to systems that can be built only from source:

For Linux on PowerPC 64-bit, the minimum supported kernel version is 2.6.37, meaning that
Go does not support CentOS 6 on these systems.

Install Go compiler binaries for bootstrap

The Go toolchain is written in Go. To build it, you need a Go compiler installed.
The scripts that do the initial build of the tools look for a "go" command
in $PATH, so as long as you have Go installed in your
system and configured in your $PATH, you are ready to build Go
from source.
Or if you prefer you can set $GOROOT_BOOTSTRAP to the
root of a Go installation to use to build the new Go toolchain;
$GOROOT_BOOTSTRAP/bin/go should be the go command to use.

There are four possible ways to obtain a bootstrap toolchain:

Download a recent binary release of Go.

Cross-compile a toolchain using a system with a working Go installation.

Use gccgo.

Compile a toolchain from Go 1.4, the last Go release with a compiler written in C.

These approaches are detailed below.

Bootstrap toolchain from binary release

To use a binary release as a bootstrap toolchain, see
the downloads page or use any other
packaged Go distribution.

Bootstrap toolchain from cross-compiled source

To cross-compile a bootstrap toolchain from source, which is
necessary on systems Go 1.4 did not target (for
example, linux/ppc64le), install Go on a different system
and run bootstrap.bash.

When run as (for example)

$ GOOS=linux GOARCH=ppc64 ./bootstrap.bash

bootstrap.bash cross-compiles a toolchain for that GOOS/GOARCH
combination, leaving the resulting tree in ../../go-${GOOS}-${GOARCH}-bootstrap.
That tree can be copied to a machine of the given target type
and used as GOROOT_BOOTSTRAP to bootstrap a local build.

Bootstrap toolchain using gccgo

To use gccgo as the bootstrap toolchain, you need to arrange
for $GOROOT_BOOTSTRAP/bin/go to be the go tool that comes
as part of gccgo 5. For example on Ubuntu Vivid:

$ sudo apt-get install gccgo-5
$ sudo update-alternatives --set go /usr/bin/go-5
$ GOROOT_BOOTSTRAP=/usr ./make.bash

Bootstrap toolchain from C source code

To build a bootstrap toolchain from C source code, use
either the git branch release-branch.go1.4 or
go1.4-bootstrap-20171003.tar.gz,
which contains the Go 1.4 source code plus accumulated fixes
to keep the tools running on newer operating systems.
(Go 1.4 was the last distribution in which the toolchain was written in C.)
After unpacking the Go 1.4 source, cd to
the src subdirectory, set CGO_ENABLED=0 in
the environment, and run make.bash (or,
on Windows, make.bat).

Once the Go 1.4 source has been unpacked into your GOROOT_BOOTSTRAP directory,
you must keep this git clone instance checked out to branch
release-branch.go1.4.  Specifically, do not attempt to reuse
this git clone in the later step named "Fetch the repository."  The go1.4
bootstrap toolchain must be able to properly traverse the go1.4 sources
that it assumes are present under this repository root.

Note that Go 1.4 does not run on all systems that later versions of Go do.
In particular, Go 1.4 does not support current versions of macOS.
On such systems, the bootstrap toolchain must be obtained using one of the other methods.

Install Git, if needed

To perform the next step you must have Git installed. (Check that you
have a git command before proceeding.)

If you do not have a working Git installation,
follow the instructions on the
Git downloads page.

(Optional) Install a C compiler

To build a Go installation
with cgo support, which permits Go
programs to import C libraries, a C compiler such as gcc
or clang must be installed first. Do this using whatever
installation method is standard on the system.

To build without cgo, set the environment variable
CGO_ENABLED=0 before running all.bash or
make.bash.

Fetch the repository

Change to the directory where you intend to install Go, and make sure
the goroot directory does not exist. Then clone the repository
and check out the latest release tag (go1.12,
for example):

$ git clone https://go.googlesource.com/go goroot
$ cd goroot
$ git checkout <tag>

Where <tag> is the version string of the release.

Go will be installed in the directory where it is checked out. For example,
if Go is checked out in $HOME/goroot, executables will be installed
in $HOME/goroot/bin. The directory may have any name, but note
that if Go is checked out in $HOME/go, it will conflict with
the default location of $GOPATH.
See GOPATH below.

Reminder: If you opted to also compile the bootstrap binaries from source (in an
earlier section), you still need to git clone again at this point
(to checkout the latest <tag>), because you must keep your
go1.4 repository distinct.

(Optional) Switch to the master branch

If you intend to modify the go source code, and
contribute your changes
to the project, then move your repository
off the release tag, and onto the master (development) branch.
Otherwise, skip this step.

$ git checkout master

Install Go

To build the Go distribution, run

$ cd src
$ ./all.bash

(To build under Windows use all.bat.)

If all goes well, it will finish by printing output like:

ALL TESTS PASSED

---
Installed Go for linux/amd64 in /home/you/go.
Installed commands in /home/you/go/bin.
*** You need to add /home/you/go/bin to your $PATH. ***

where the details on the last few lines reflect the operating system,
architecture, and root directory used during the install.

For more information about ways to control the build, see the discussion of
environment variables below.
all.bash (or all.bat) runs important tests for Go,
which can take more time than simply building Go. If you do not want to run
the test suite use make.bash (or make.bat)
instead.

Testing your installation

Check that Go is installed correctly by building a simple program.

Create a file named hello.go and put the following program in it:

package main

import "fmt"

func main() {
	fmt.Printf("hello, world\n")
}

Then run it with the go tool:

$ go run hello.go
hello, world

If you see the "hello, world" message then Go is installed correctly.

Set up your work environment

You're almost done.
You just need to do a little more setup.

How to Write Go Code
Learn how to set up and use the Go tools

The How to Write Go Code document
provides essential setup instructions for using the Go tools.

Install additional tools

The source code for several Go tools (including gopls)
is kept in the golang.org/x/tools repository.
To install one of the tools (gopls in this case):

$ go install golang.org/x/tools/gopls@latest

Community resources

The usual community resources listed on the help page have
active developers that can help you with problems with your installation or your
development work.
For those who wish to keep up to date,
there is another mailing list, golang-checkins,
that receives a message summarizing each checkin to the Go repository.

Bugs can be reported using the Go issue tracker.

Keeping up with releases

New releases are announced on the
golang-announce
mailing list.
Each announcement mentions the latest release tag, for instance,
go1.9.

To update an existing tree to the latest release, you can run:

$ cd go/src
$ git fetch
$ git checkout <tag>
$ ./all.bash

Where <tag> is the version string of the release.

Optional environment variables

The Go compilation environment can be customized by environment variables.
None is required by the build, but you may wish to set some
to override the defaults.

$GOROOT

The root of the Go tree, often $HOME/go1.X.
Its value is built into the tree when it is compiled, and
defaults to the parent of the directory where all.bash was run.
There is no need to set this unless you want to switch between multiple
local copies of the repository.

$GOROOT_FINAL

The value assumed by installed binaries and scripts when
$GOROOT is not set explicitly.
It defaults to the value of $GOROOT.
If you want to build the Go tree in one location
but move it elsewhere after the build, set
$GOROOT_FINAL to the eventual location.

$GOPATH

The directory where Go projects outside the Go distribution are typically
checked out. For example, golang.org/x/tools might be checked out
to $GOPATH/src/golang.org/x/tools. Executables outside the
Go distribution are installed in $GOPATH/bin (or
$GOBIN, if set). Modules are downloaded and cached in
$GOPATH/pkg/mod.

The default location of $GOPATH is $HOME/go,
and it's not usually necessary to set GOPATH explicitly. However,
if you have checked out the Go distribution to $HOME/go,
you must set GOPATH to another location to avoid conflicts.

$GOBIN

The directory where executables outside the Go distribution are installed
using the go command. For example,
go install golang.org/x/tools/cmd/godoc@latest downloads, builds,
and installs $GOBIN/godoc. By default, $GOBIN is
$GOPATH/bin (or $HOME/go/bin if GOPATH
is not set). After installing, you will want to add this directory to
your $PATH so you can use installed tools.

Note that the Go distribution's executables are installed in
$GOROOT/bin (for executables invoked by people) or
$GOTOOLDIR (for executables invoked by the go command;
defaults to $GOROOT/pkg/$GOOS_$GOARCH) instead of
$GOBIN.

$GOOS and $GOARCH

The name of the target operating system and compilation architecture.
These default to the values of $GOHOSTOS and
$GOHOSTARCH respectively (described below).

Choices for $GOOS are
android, darwin, dragonfly,
freebsd, illumos, ios, js,
linux, netbsd, openbsd,
plan9, solaris and windows.

Choices for $GOARCH are
amd64 (64-bit x86, the most mature port),
386 (32-bit x86), arm (32-bit ARM), arm64 (64-bit ARM),
ppc64le (PowerPC 64-bit, little-endian), ppc64 (PowerPC 64-bit, big-endian),
mips64le (MIPS 64-bit, little-endian), mips64 (MIPS 64-bit, big-endian),
mipsle (MIPS 32-bit, little-endian), mips (MIPS 32-bit, big-endian),
s390x (IBM System z 64-bit, big-endian), and
wasm (WebAssembly 32-bit).

The valid combinations of $GOOS and $GOARCH are:

	$GOOS	 $GOARCH

	aix	 ppc64

	android	 386

	android	 amd64

	android	 arm

	android	 arm64

	darwin	 amd64

	darwin	 arm64

	dragonfly	 amd64

	freebsd	 386

	freebsd	 amd64

	freebsd	 arm

	illumos	 amd64

	ios	 arm64

	js	 wasm

	linux	 386

	linux	 amd64

	linux	 arm

	linux	 arm64

	linux	 loong64

	linux	 mips

	linux	 mipsle

	linux	 mips64

	linux	 mips64le

	linux	 ppc64

	linux	 ppc64le

	linux	 riscv64

	linux	 s390x

	netbsd	 386

	netbsd	 amd64

	netbsd	 arm

	openbsd	 386

	openbsd	 amd64

	openbsd	 arm

	openbsd	 arm64

	plan9	 386

	plan9	 amd64

	plan9	 arm

	solaris	 amd64

	windows	 386

	windows	 amd64

	windows	 arm

	windows	 arm64

$GOHOSTOS and $GOHOSTARCH

The name of the host operating system and compilation architecture.
These default to the local system's operating system and
architecture.

Valid choices are the same as for $GOOS and
$GOARCH, listed above.
The specified values must be compatible with the local system.
For example, you should not set $GOHOSTARCH to
arm on an x86 system.

$GO386 (for 386 only, defaults to sse2)

This variable controls how gc implements floating point computations.

GO386=softfloat: use software floating point operations; should support all x86 chips (Pentium MMX or later).

GO386=sse2: use SSE2 for floating point operations; has better performance but only available on Pentium 4/Opteron/Athlon 64 or later.

$GOARM (for arm only; default is auto-detected if building
on the target processor, 6 if not)

This sets the ARM floating point co-processor architecture version the run-time
should target. If you are compiling on the target system, its value will be auto-detected.

GOARM=5: use software floating point; when CPU doesn't have VFP co-processor

GOARM=6: use VFPv1 only; default if cross compiling; usually ARM11 or better cores (VFPv2 or better is also supported)

GOARM=7: use VFPv3; usually Cortex-A cores

If in doubt, leave this variable unset, and adjust it if required
when you first run the Go executable.
The GoARM page
on the Go community wiki
contains further details regarding Go's ARM support.

$GOAMD64 (for amd64 only;
default is v1)

This sets the microarchitecture level for which to compile.
Valid values are v1 (default), v2, v3,
v4.
See the Go wiki
MinimumRequirements page for more information.

$GOMIPS (for mips and mipsle only)
 $GOMIPS64 (for mips64 and mips64le only)

	These variables set whether to use floating point instructions. Set to "hardfloat" to use floating point instructions; this is the default.  Set to "softfloat" to use soft floating point.

$GOPPC64 (for ppc64 and ppc64le only)

This variable sets the processor level (i.e. Instruction Set Architecture version)
for which the compiler will target. The default is power8.

GOPPC64=power8: generate ISA v2.07 instructions

GOPPC64=power9: generate ISA v3.00 instructions

$GOWASM (for wasm only)

	This variable is a comma separated list of experimental WebAssembly features that the compiled WebAssembly binary is allowed to use.
	The default is to use no experimental features.

GOWASM=satconv: generate saturating (non-trapping) float-to-int conversions

GOWASM=signext: generate sign-extension operators

Note that $GOARCH and $GOOS identify the
target environment, not the environment you are running on.
In effect, you are always cross-compiling.
By architecture, we mean the kind of binaries
that the target environment can run:
an x86-64 system running a 32-bit-only operating system
must set GOARCH to 386,
not amd64.

If you choose to override the defaults,
set these variables in your shell profile ($HOME/.bashrc,
$HOME/.profile, or equivalent). The settings might look
something like this:

export GOARCH=amd64
export GOOS=linux

although, to reiterate, none of these variables needs to be set to build,
install, and develop the Go tree.

redpajama_set_name: RedPajamaGithub


text:
PRAYERS AND TEXTS FOR 2022
OUR PARISH, OUR PLANET
ST. JOSEPH'S SEMINARY AT 125
Keeper of the Books
JOINED IN SPIRIT
RETURN OF THE FAITHFUL
Weighing Risks
VENERABLE PIERRE TOUSSAINT
JOYFUL PASSAGES
A TIME TO (RE)BUILD
A TIME TO GATHER
A TIME TO SERVE
A TIME TO HEAL
A TIME TO LEARN
A TIME TO UNITE
A TIME TO GROW
REVEALING GOD'S LOVE
SAINTS OF NEW YORK
State of Holiness
HEROES OF NEW YORK
ART'S CONSOLATIONS
HOPE FOR THE HOMELESS
DANCING TO HEAVEN
YOUNG & CATHOLIC
GIVE/RECEIVE
ONE CHRIST, MANY WELCOMES
WOMEN OF THE CHURCH
STRANGERS AT THE GATE
A TALE OF TWO ORGANS
HARVEST OF FAITH
Sowing Charity
Minding Our Footprint
REASONS TO BE JOYFUL
ONE-DAY PILGRIMAGES
DOROTHY DAY'S LEGACY
THE MANY MERCIES OF ARCHCARE
Handling the Costs
FAITH, LOVE AND SWEAT
NO HANDS BUT OURS
PRIESTHOOD NOW
SAYING YES TO CHRIST
BLESSED VS. STRESSED
TABLE OF PLENTY
CHANNELING PEACE
MIND, HEART AND SOUL
CATHOLIC CHARITIES AT 101
FOOD FOR THE JOURNEY
Father Keller's Candles
Maggi's List
Five Books for Under the Tree
Beyond the Beach Read
The Light of Day
For Gift-Giving Season
The Christopher Awards
Is Advent a time of fasting or feasting?
What is a cardinal's role in the Catholic Church?
What is an indulgence?
Eucharistic adoration: origins and purpose
What is Paschal Time?
Pandemics and the Church: a history
Baptism: Can a lay person perform one?
Why not virtual sacraments?
Cremation and Catholic doctrine
A tale of two Creeds
Make a civil marriage Catholic
What is a relic? Why venerate them?
Altar bells at Mass, explained
Why we pray to saints
What is Ordinary Time?
Setting the Stage for First Communion: A Bedtime Q&A
Mary's days of obligation
How do adults join the Catholic Church?
How is Halloween significant to Catholics?
Should I become a deacon?
Why is May the Month of Mary?
How does a nun get her name?
What is a see (as in Holy See)?
What is an archdiocese?
AN ADVENT MEDITATION
FROM THE CARDINAL
WINTER 2019–2020
MAGAZINE EXPERIENCE
THE MAGAZINE OF THE ARCHDIOCESE OF NEW YORK
PASSING, SHOOTING, RUNNING, THINKING, GROWING, PRAYING: CYO UPS ITS GAME
PARENTS AND FRIENDS HAVE TAKEN THEIR PLACES in bleachers or chairs. The girls or boys trot over anxiously to the team benches after their opening warmup, shaking off pre-game nerves. The referees confer briefly at midcourt. The pregame clock winds down, a horn sounds, but instead of taking the floor to start the game, the players, coaches and refs all gather beneath a signboard at one end of the gym. The coaches lead them in the sign of the cross, and they intone in unison:
Lord Jesus, let all gathered here today know that we do so in your name;
allow us to understand the true meaning of our participation
in this Catholic Youth Organization activity.
Make us aware of our responsibility to all concerned
so we may grow and develop in the full reality of Christian formation.
Grant us a personal acceptance of the dignity of all individuals.
Above all, let us, in all things, demonstrate a spirit of love and respect for all.
This scene happens hundreds of times each weekend in gyms around the Archdiocese of New York, with children from fourth through eighth grades – the bold, natural athletes and the quiet, hopeful learners. The prayer ends and all head to positions on the court or bench; the whistle blows, the referee tosses the ball for the tip-off. The game is on.
It was the Great Depression which gave rise to the founding of the Catholic Youth Organization, whose first chapter was instituted in Chicago in 1930. Grounded in Catholic social teachings, the program was designed to lead young people away from the unhealthy, amoral culture of the streets toward faith and physical health. In December 1936, John Cardinal Hayes announced the establishment of the CYO in New York. "We must be watchful shepherds," he noted in encouraging every parish to start a CYO program. "All Catholic children – those in public as well as those in Catholic Schools – are our charges, yours and mine."
CYO of the Archdiocese of New York – now a division of Catholic Charities Community Services – has undergone significant change since Cardinal Hayes inaugurated it some 82 years ago. The social events that once were part of the program have become the province of youth ministry groups. Today, the best-known CYO program is basketball, with 17,000 boys and girls playing in the winter season and an additional 2,300 in the new spring league.
During winter, hundreds of games are played each weekend across the archdiocese. The program, however, is not primarily focused on racking up wins or even on the development of basketball skills. Its main goal is to develop Christian values in players: fairness, honesty, respect, discipline, kindness and a spirit of loving competition. "Learning how to lose is just as important as learning how to win," according to CYO New York's statement of purpose, and "learning how to win graciously is more important than winning itself."
"CYO is not just basketball," says Father Joseph P. LaMorte, vicar general and chancellor of the Archdiocese of New York and a former pastor in Poughkeepsie and Garnerville. "In addition to teaching sportsmanship and fair play, its many programs build character and maturity. At the parishes in which I have served, I was always grateful for the presence of the CYO."
The program's values are not just taught on the court. "CYO promotes community by having players attend Mass together, collect food for the needy and prepare dinner at a local soup kitchen," says John Hannaway, CYO coordinator at Sts. John and Paul Parish in Larchmont. "It shows that the Church and the parish are worthy focal points for our activities."
Every Catholic child needs this sort of education, but not every child plays basketball. For this reason, CYO New York is going through some changes. "We're taking our values and expanding our programs to allow other kids the opportunity to participate," says Seth Peloso, interim director.
For children interested in running, the track programs currently serve 2,500 boys and girls in seven counties. "Our track and field archdiocesan championships take place at Carl Icahn Stadium on Randall's Island, and we have regional cross-country meets at Van Cortlandt Park in the Bronx," Peloso says. "The teams have also competed at Walt Disney World in Orlando. We're hoping to expand into more counties in the next couple of years."
Since most racing events, unlike basketball, are individual, there's no sitting on the bench; every kid gets to run and work on individual accomplishments while also being part of a team. "It doesn't matter what place they finish," writes Stefan Anikewich, the volunteer coach for CYO Track Club, whose team has runners from all over Westchester and the Bronx. "We always look for the real wins: enthusiasm, hard work, attention to running mechanics, achievable goals, teamwork, good sports-(woman/man)-ship, community awareness and using a TON of heart."
Few are aware that CYO also has programs for volleyball (in Ulster and Dutchess counties), bowling (on Staten Island), golf (in Ulster County and on Staten Island) and cheerleading (30 teams on Staten Island and in the Bronx). Beyond athletics, CYO sponsors Boy and Girl Scout troops, an annual art and essay contest, and chess programs in 30 schools.
"Chess is an area where we can expand our reach," Peloso says. "Its benefits – the development of logic and strategy skills – are also critical skills in life."
Peloso looks forward to a future serving more and more kids. "We're now embarking on a plan to determine how best to serve youth in today's society," he says. With all the negative influences in our current tech-dominated culture, that's good news for parents.
For more information, visit cyony.org. For information on how to start a new program in your parish or region, contact Seth Peloso at Seth.Peloso@archny.org or 646-794-2050.
Archways magazine is published by the Archdiocese of New York Marketing Office © 2022


Along with nine extraordinary women, we share with you our stories from surviving to thriving through yoga & meditation. Yoga goes beyond flexing and stretching, and meditation is far more than just sitting and relaxing. Here, our stories show you how the magnificent power of Yoga can help you develop resilience to life's hardships.
Hardcopy will be available soon!


text:
Betty White: 'You Don't Give Up' and 4 Other Pieces of Sage Advice From the Beloved Star
Published December 31, 2021 • Updated on January 3, 2022 at 9:31 am
Gus Ruelas | Reuters
In 2018, Betty White, who died at age 99 on Friday, told Parade that she'd like to be remembered "warmly," and with a laugh.
White was indeed widely loved for her positivity and sass. But she also had a legendary work ethic: As of 2014, White held the Guinness World Records record for Longest TV Career for a Female Entertainer. She made her small screen debut in 1939 and starred in myriad hits from "The Mary Tyler Moore Show" and "The Carol Burnett Show" to "The Golden Girls" and "Hot in Cleveland." She even hosted "Saturday Night Live" at age 88. According to IMDB.com, White's most recent television role was in 2019, as the voice of character "Bitey White" on TV short, "Forky Asks a Question."
Over the years, the actress had sage advice about both life and work. In honor of White and her long life and career, here are some of her best bits of wisdom.
DONALD TRUMP 15 mins ago
January 6 Riot Probe to Get 4 Pages of Trump White House Documents While His Lawyer Threatens Legal Action
New York 16 mins ago
This 24-Year-Old Lost Her Waitressing Job. Now She Makes $8,600 Per Month in Passive Income—and Works 'Just 2 Hours a Day'
"Everybody needs a passion. That's what keeps life interesting," White wrote in her 2011 book, "If You Ask Me (And of Course You Won't)."
"If you live without passion, you can go through life without leaving any footprints."
Be an optimist. "Just looking at the positive side and not dwelling on the downside. Takes up too much energy being negative," she told People in January.
And a sense of humor is critical, she said. "Don't take yourself too seriously. You can lie to others … but you cannot lie to yourself."
On determination
According to Parade, White was repeatedly turned down when she first tried to make it as an actress, as she was considered "unphotogenic." Obviously, she persevered.
"You just keep plugging away," White told Parade in 2018. "You don't give up."
On work and interests
White, who once said that the word "retirement" was not part of her vocabulary, told Katie Couric in 2017 that it's important to stay busy.
"It's not hard to find things you're interested in, but enjoy them and indulge them, and I think that can keep you on your toes," White said.
On career advice
White's career advice to young people was do the work and be prepared, she told Parade in 2018. "Don't think you can wing it, because you can't," she said.
Even in show business, it's "fun, but take your business seriously, because it is a serious business," she said.
Don't miss: Colin Powell: 'Get mad, and then get over it,' and 12 other rules he lived and worked by
Why these 4 high-achievers chose to share their mental health struggles
Feeling burned out? Here's how to ensure you're refreshed for the new year
Why the pressure to set New Year's resolutions might feel greater than ever
Betty WhiteMake ItentertainmentEntrepreneurshipMake It - Life


Joe Matanoski has been a professor of biology at Stevenson University in Owings Mills for many years. In 2007 his colleague, former Soldiers Delight Conservation, Inc. board member Claudia Floyd, also a faculty member at Stevenson at the time, told Joe about the unusual geological and biological features of the nearby Soldiers Delight Natural Environment Area.
Joe visited Soldiers Delight to check out the hiking trails and our visitor center. He was fascinated by the site's significance as the largest remaining serpentine barrens on the east coast, which had just recently earned a state wildlands designation, offering the biodiverse ecosystem further protections from encroachment and development. Joe knew he had to find a way to weave Soldiers Delight's many attributes into his biology curriculum at school.
Since 2008, Professor Matanoski has used Soldiers Delight as an educational resource at Stevenson University, teaching his students about the unique characteristics of the site. Since 2010, Joe has conducted research, with the blessing of the Maryland State ecologist in charge of Soldiers Delight, on the some of the area's rare species of flora and on the long-term effects of deer browsing on both aboveground vegetation and seed bank composition in plant communities. Only two students at a time are permitted to join the professor in conducting his botanical and biological studies in the highly sensitive habitat.
In 2007, Joe became a member of the SDCI board of directors so that he could further his commitment to providing greater knowledge and understanding of the Soldiers Delight preserve for everyone. In addition to his instructional support, since 2008 Joe has been recruiting and providing student volunteers for twice yearly restoration efforts at the Natural Environment Area.
That kind of sustained dedication to the valuable resource we know as Soldiers Delight is what makes our board of directors and the core mission of the SDCI Friends group so indispensable. Joe's assistance in ferreting out best practices with regard to restoring some of the rarest species of flora on the serpentine barrens is essential to our purpose.
Soldiers Delight Conservation, Inc., (SDCI) is a volunteer non-profit group, formed in 1959, whose mission is to educate the public about Soldiers Delight and to conserve and restore its rare and endangered ecosystem for future generations. We serve as the "Friends" group for the Soldiers Delight Natural Environment Area.
Copyright ©2005-2019 by Soldiers Delight Conservation, Inc. All Rights Reserved.