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text:
\section{Introduction}
\label{sec:intro}
The XENON1T experiment has recently reported excess events with more than 3$\sigma$ significance~\cite{Aprile:2020tmw}. An attractive explanation is that a new light particle, such as an axion-like particle (ALP) or a dark photon, with a coupling to the electron is produced in the Sun and absorbed by the XENON detector~\cite{An:2014twa}.  Ref.~\cite{Aprile:2020tmw} also explores other scenarios: bosonic dark matter, non-standard neutrino interaction, and tritium concentration.

The solar interpretations of the excess, however, are inconsistent with various stellar cooling bounds~\cite{Raffelt:1996wa, Redondo:2008aa, An:2013yfc, Giannotti:2015kwo, Hardy:2016kme, Giannotti:2017hny},
because the very interaction that produces the new particle at the sun and allows it to be detected by the XENON1T experiment also produces it in other stars such as horizontal branch (HB) stars and red giants (RG)\@.
This would increase the cooling rates of those stars and contradict with observations~\cite{An:2020bxd, Gao:2020wer,  Aprile:2020tmw,DiLuzio:2020jjp,Bloch:2020uzh,Budnik:2020nwz,Athron:2020maw}.

\begin{figure}[t]
 \begin{center}
  \hspace*{-1em}
  \includegraphics[width=0.47\textwidth]{plot1.pdf}
\caption{An illustration of our scenario. In the vacuum/sun, the dark photon mass, $m_{A'}$, and its kinetic mixing with the photon, $\epsilon$, take the values matching the XENON1T excess, given by the small oval~\cite{Bloch:2020uzh}.
Inside HB/RG star cores, the electron density $n_e$ exceeds a critical value $n_{\rm c}$ and $\epsilon$ vanishes, as represented by the arrow, evading the HB/RG bounds \cite{An:2014twa}.
}
 \label{fig:bestfit}
 \end{center}
 \end{figure}

In this paper, we propose a solar interpretation of the XENON1T excess with a dark photon that can avoid the stellar cooling constraints.
Our scenario is illustrated in Fig.~\ref{fig:bestfit},
where the two axes corresponds to the dark photon mass, $m_{A'}$, and the kinetic mixing, $\epsilon$, between the dark and SM photons.
In the vacuum as well as in the sun,
$m_{A'}$ and $\epsilon$ take the values that match the XENON1T excess~\cite{Bloch:2020uzh}, represented by the small oval.
On the other hand, in a denser environment such as the core of a HB or RG star, where the electron number density $n_e$ exceeds a critical value $n_{\rm c}$,
$\epsilon$ vanishes and takes us out of the stellar cooling bounds, as indicated by the downward arrow.

We realize this scenario by promoting $\epsilon$ to a dynamical operator $\phi(x) / \Lambda'$ with some mass scale $\Lambda'$ and a scalar field $\phi$ whose expectation value depends $n_e$.
This is achieved by having the mass-squared parameter of $\phi$ depend on $n_e$ as $m^2 = -\mu_\phi^2 + m_e \bar{e} e / \Lambda^2$, where $\mu_\phi$ and $\Lambda$ are chosen such that $n_{\rm c}$ falls between the solar and HB densities.%
\footnote{The operator $\bar{e} e$ is not exactly equal to the electron number density, $\bar{e} \gamma^0 e$,
but they are nearly equal for nonrelativistic electrons with velocities $v \ll 1$ as the difference between them are $O(v^2)$. We ignore this difference throughout our analysis.}

This idea will be fully developed in Sec.~\ref{sec:dark} as an effective field theory (EFT) and its phenomenological constraints as well as theoretical consistency will be studied.
In particular, while obtaining the right phenomenology requires the tree-level potential for $\phi$ to be extremely flat, we will show that the flatness is nonetheless maintained even under loop corrections,
except for the fine tuning of the $\phi$ mass as expected for the mass of an elementary scalar field not protected by a symmetry.
We believe this is the first model in the literature on a density-dependent solar interpretation of the XENON1T anomaly without the cooling problems that does not suffer from too large quantum corrections destroying the flatness of the potential.
As for other directions for a solar interpretation of the excess,  it is also possible to exploit {\it composition difference} (i.e., H versus He) between the sun and denser stars instead of density differences~\cite{McKeen:2020vpf}.

We will discuss the UV completion of the EFT in Sec.~\ref{sec:UV}, where we present a general argument that the allowed range of parameters in the EFT necessarily point to the existence of new electrically charged particles with sub-TeV masses in any UV-complete realization of the EFT\@.
This offers unexpected additional experimental probes into our scenario by laboratory experiments.

While our scenario is not the only way to use density dependence,
we will discuss advantages of our scenario over other similar ideas as well as earlier work on density dependent interactions in the context of solar interpretation of the XENON1T excess~\cite{Bloch:2020uzh, DeRocco:2020xdt} in Sec.~\ref{sec:difficulties}, focusing on the stability of the flat potential under quantum corrections.

\section{The Dark Photon Model}
\label{sec:dark}
In this section, we provide a simple explicit model that realizes the scenario described in Sec.~\ref{sec:intro}.
We begin by an effective field theory (EFT) that is self-consistent and suffices to study phenomenological implications of our scenario.
The UV completion of the EFT will be discussed in Sec.~\ref{sec:UV}.

\subsection{The effective Lagrangian}
The EFT introduces two new degrees of freedom beyond the SM: a massive spin-1 field, $A'_\mu$, and a real scalar field, $\phi$.
The tree-level effective Lagrangian is given by
\begin{align}
{\cal L}
= {\cal L}_\text{SM}
+ {\cal L}_\text{kin}^{A'\phi}
+ \frac{m_{A'}^2}{2} A'^2
- \frac{\phi}{2\Lambda'} B^{\mu\nu} F'_{\mu\nu}
- V(\phi)
\,,\label{eq:Lagrangian}
\end{align}
where ${\cal L}_\text{kin}^{A'\phi}$ is just the canonically normalized kinetic terms of $A'$ and $\phi$, while $B_{\mu\nu}$ and $F'_{\mu\nu}$ are the field strength tensors for the SM hypercharge gauge field and $A'$, respectively.
It is essential here that ${\cal L}_\text{kin}^{A'\phi}$ does {\it not} contain the ``bare'' kinetic mixing term, $B^{\mu\nu} F'_{\mu\nu}$, as we want the mixing to be entirely induced by $\langle \phi \rangle$.
The absence of the bare mixing is consistent within the EFT
as the Lagrangian~\eqref{eq:Lagrangian} has the following $Z_2$ symmetry:
\begin{eqnarray}
\phi \to -\phi
\quad\text{and}\quad
A'_\mu \to -A'_\mu
\label{eq:Z_2}
\end{eqnarray}
with all other fields unchanged.
A possible UV origin of this $Z_2$ symmetry will be discussed in Sec.~\ref{sec:UV}.
The dependence of $\langle \phi \rangle$ on the electron density comes from
\begin{eqnarray}
V(\phi)
= \frac{1}{2} \!\left(
- \mu_\phi^2
+ \frac{y_e H \bar{\ell}_{\rm L} e_{\rm R} + \text{h.c.}}{\Lambda^2}
\right)\! \phi^2 + \frac{\lambda_\phi}{4!} \phi^4
\,,\label{eq:Vphi}
\end{eqnarray}
where, upon electroweak symmetry breaking, the numerator of $\Lambda^2$ picks up an electron density dependence:
\begin{align}
y_e \langle H \rangle \bar{\ell}_{\rm L} e_{\rm R} + \text{h.c.}
= m_e \bar{e} e
\,.
\end{align}

In the vacuum and the core of the sun,
we would like the the density-dependent term, $m_e \bar{e} e / \Lambda^2$, to be negligible compared to $\mu_\phi^2$ in the potential~\eqref{eq:Vphi}.
In these environments, we have $\langle \phi \rangle = v_0 \neq 0$ and
an effective $\gamma$-$A'$ mixing is induced:
\begin{eqnarray}
{\cal L}_\text{induced} = -\frac{\epsilon}{2} F^{\mu\nu} F'_{\mu\nu}
\quad\text{with}\quad
\epsilon \equiv \frac{v_0 \cos\theta_w}{\Lambda'}
\,,
\label{eq:mixing}
\end{eqnarray}
where $\theta_w$ is the electroweak mixing angle.
The best fit values of $m_{A'}$ and $\epsilon$ to the XENON1T excess were found by Ref.~\cite{Bloch:2020uzh} to be
\begin{eqnarray}
m_{A'} = 2.3\,{\rm keV}
\,,\quad
\epsilon = 2.5 \times 10^{-13}\,.
\label{eq:XENON1T_best_fit}
\end{eqnarray}

On the other hand, in denser stars, we would like the density-dependent term to dominate over $\mu_\phi^2$
so that we have $\langle \phi \rangle = 0$ and thereby turn off $\gamma$-$A'$ mixing.
Let $n_{\rm c}$ be a critical density at which the coefficient of $\phi^2$ in the potential~\eqref{eq:Vphi} changes the sign.
Since the electron number densities in the cores of the sun and a typical HB star are respectively $\sim 6 \times 10^2\>{\rm keV}^3$ and $\sim 4 \times 10^4\>{\rm keV}^3$~\cite{Hardy:2016kme},
$n_{\rm c}$ should be between these densities, e.g., $4 \times 10^3\>{\rm keV}^3$.
We then have
\begin{eqnarray}
\mu_\phi
= \frac{\sqrt{m_e n_{\rm c}}}{\Lambda}
\,.\label{eq:mu_phi}
\end{eqnarray}
Then, from $\lambda_\phi=6\mu_\phi^2/v_0^2$
 with the relation~\eqref{eq:mixing} to eliminate $v_0$,
this is equivalent to
\begin{align}
\lambda_\phi = \frac{6 m_e n_{\rm c} \cos^{2\!}\theta_w}{\epsilon^2 \Lambda^2 \Lambda'^2}
\,.\label{eq:lambda_phi}
\end{align}
From Eqs.~\eqref{eq:mu_phi} and~\eqref{eq:lambda_phi}, we will see the generic feature of our parameter space that the values of $\mu_\phi$ and $\lambda_\phi$ tend to be very small because it will turn out that $\Lambda'\gtrsim10^9\,{\rm GeV}$ and $\Lambda\gtrsim10^7\,{\rm GeV}$.

\subsection{Phenomenological constrants}
We now discuss constraints on our model.
While the HB/RG bounds on the dark photon are evaded by construction,
we must require $\phi$ not to be produced in stars.
This requirement must be analyzed separately for the sun and the HB/RG cases
as $\langle \phi \rangle = v_0$ for the former while $\langle \phi \rangle = 0$ for the latter.

In the sun, we have $\phi = v_0 + \varphi$, where $\varphi$ can be singly produced through an effective Yukawa interaction with electrons, $y_{\rm eff} \, \varphi \bar{e} e$, with $y_{\rm eff} = m_e v_0 / \Lambda^2$.
Such emission from the sun is constrained by XENON1T S2-only analyses~\cite{Budnik:2019olh}, and it
gives a strong
bound on $y_{\rm eff}$ in the $\langle \phi \rangle = v_0$ case.
There is a stronger bound by RG star cooling~\cite{Hardy:2016kme}
but it is irrelevant here as it is derived from denser stars in which $\langle \phi \rangle = 0$.
Parametrizing the solar bound as $y_{\rm eff} < 10^{-15} \,Y$ (with $Y \simeq 2$ currently from Ref.~\cite{Budnik:2019olh}),
we obtain
\begin{align}
\frac{\Lambda'}{\Lambda^2} <
7\,Y \,
\frac{2.5\times10^{-13}}{\epsilon}
\>{\rm GeV}^{-1}
\,.\label{phi_emission_constraint}
\end{align}
We use this relation between $\Lambda$ and $\Lambda^\prime$ to rule out the area shown by the green region in Fig.~\ref{fig:moneyplot}.

On the other hand, in a dense star like HB or RG, $\langle \phi \rangle$ vanishes so the unbroken $Z_2$ requires $\phi$ to be produced
always in pairs or in association with $A'$.
For the $\phi$ pair production,
compared to the single $\varphi$ production case above, the presence of an extra $\phi$ in the final state implies that
the $\phi$ pair production rate is roughly given by the single $\varphi$ production rate with $y_{\rm eff}$ replaced with $y'_\text{eff} \equiv m_e T/(4\pi\Lambda^2)$,
where $T$ is the core temperature of the star ($T \sim 10\>{\rm keV}$ for a typical HB/RG)\@.
With the strongest bound $y'_\text{eff} <7\times10^{-16}$ from RG stars~\cite{Hardy:2016kme},
we get $\Lambda\gtrsim$~TeV but
we will see that there are much stronger constraints from fifth force/equivalence principle tests.

Similarly, the emission of $\phi$-$A'$ pairs can contribute to stellar cooling.
We can estimate the $\phi$-$A'$ production rate $\Gamma_{\phi A'}$ as
\begin{equation}
    \Gamma_{\phi A'}(m_{A'})\sim \frac{1}{16\pi^2}\frac{T^2}{\Lambda'^2} \frac{\Gamma_{A'}(M_{\phi A'})}{\tilde{\epsilon}^2} \,,
\end{equation}
where $T$ is the temperature of the star, while $\Gamma_{A'}(M_{\phi A'})$ is the would-be production rate of a single dark photon with mass $M_{\phi A'}$ and mixing $\tilde{\epsilon}$, where $M_{\phi A'}$ is the invariant mass of the $\phi$-$A'$ system.
To be conservative, we take  $M_{\phi A'}\sim m_{\rm peak}$ with $m_{\rm peak}$ being where the cooling rate is maximized in Fig.~1 of  Ref.~\cite{An:2020bxd}. We then get
\begin{equation}
\frac{T_{\rm HB/RG}}{4\pi\Lambda'}\lesssim 6\times10^{-16}
~~\Rightarrow~~
\Lambda'\gtrsim10^9\,{\rm GeV}
\,.
\label{eq:phiAprod}
\end{equation}
This excludes the horizontal grey region in Fig.\,\ref{fig:moneyplot}

Because of the large lower bound of $\Lambda$, $\phi$ needs to be very light (see Eq.\,\eqref{eq:mu_phi}).
Such light $\phi$ provides an additional long-range force, and we find that fifth force experiments and equivalence principle tests give the strongest bound on $y_{\rm eff}$ and $m_\phi=\sqrt{2}\mu_\phi$ of our model.
We convert the bounds obtained in Ref.\,\cite{Wise:2018rnb,Kapner:2006si,Salumbides:2013dua, Schlamminger:2007ht} to our parameters (see the brown and blue regions in Fig.\,\ref{fig:moneyplot}).

In addition, the mass of a light scalar field with a small self interaction can be constrained by black hole superradiance.
However, based on the analysis of Ref.\,\cite{Arvanitaki:2014wva}, our self-coupling $\lambda_\phi$ is not small enough to maintain  superradiance, which requires $\lambda_\phi \lesssim 10^{-65}$.
Therefore, black hole superradiance does not give a relevant constraint on our scenario.

Next, the presence of the $\bar{e}e\phi^2$ term in the potential~\eqref{eq:Vphi} predicts that the electron mass depends on $\langle \phi \rangle$.
In an environment denser than $n_{\rm c}$,
the electron mass
changes as
\begin{align}
\frac{m_e^{\rm dense} - m_e}{m_e}
&= -\frac12 \Bigl( \frac{v_0}{\Lambda} \Bigr)^{\!2}
\nonumber\\
&\simeq
-4 \times 10^{-26}
\!\left( \frac{\Lambda'}{\Lambda} \right)^{\!2}
\!\left( \frac{\epsilon}{2.5\times 10^{-13}} \right)^{\!2}
.\label{eq:electronmasscorrection}
\end{align}
In the sun, the deviation is further suppressed by a factor of ${n_e^\odot}/{n_{\rm c}}$, where $n_e^\odot \sim 10^2\>{\rm keV}^3$.
This is an unobservably small deviation because the fifth-force/equivalence principle bounds prevent us from enhancing the deviation to an observable level by having a large hierarchy between $\Lambda'$ and $\Lambda$.

\begin{figure}[t!]
 \begin{center}
  \includegraphics[width=0.5\textwidth]{plot2.pdf}
 \end{center}
 \vspace{-10pt}
\caption{Constraints on the parameter space of the dark photon model of Sec.~\ref{sec:dark} for $\epsilon = 2.5 \times 10^{-13}$, $n_{\rm c} = 4 \times 10^3~{\rm keV}^3$, and $Y=2$.
The shaded region in green is excluded by the XENON1T S2-only analysis (Eq.~\eqref{phi_emission_constraint}),
while the regions in brown and blue by fifth force and equivalence principle (EP) tests, respectively.
The red and yellow regions suffer from too large quantum corrections (Eqs.~\eqref{eq:twoloopconst} and \eqref{eq:gaugebosonloop}, respectively).
The gray region shows a conservative bound from $\phi A'$ production (Eq.~\eqref{eq:phiAprod}).
Below the dashed brown line, $\langle\phi\rangle$ would be controlled by the nucleon density instead of the electron density (Eq.~\eqref{eq:nucleon}).
The dotted lines show the values of $\lambda_\phi$ (Eq.~\eqref{eq:lambda_phi}).
}
\label{fig:moneyplot}
\end{figure}

\subsection{Constraints from radiative corrections}
Finally, as we can see in the small values of $\mu_\phi$ and $\lambda_\phi$ in Fig.~\ref{fig:moneyplot}, we need a very flat potential for $\phi$,
which requires us to check that the flatness is not destroyed by loop corrections.
While the coefficient of $\phi^2$ needs to be tuned as expected for any elementary scalar whose mass is not protected by any symmetry,
we would like to avoid having to keep tuning
the coefficients of $\phi^4$, $\phi^6$, $\phi^8$, \ldots, to maintain the flatness of the potential at loop level.

First, we  investigate the 1-loop Coleman-Weinberg (CW) potential induced from $\gamma/Z/A'$ loops.
The largest contributions come from integrating out $Z$ and are given in dimensional regularization by
\begin{equation}
\Delta V_g
= \frac{3}{64\pi^2}(M_Z^2)^2 \, \ln{\frac{M_Z^2}{\mu^2}}
\,,\label{eq:CWgaugeboson}
\end{equation}
where  we have absorbed the scheme-dependent constant term in the normalization of $\mu$.
The field dependent $Z$ mass, in the limit of neglecting $m_{A'}$ with respect to $m_Z$ but to all orders in $\phi / \Lambda'$,  is given by
\begin{equation}
M_Z^2
= m_Z^2 \!\left(
1 +
\frac{(\phi / \Lambda')^2}
     {1 - (\phi / \Lambda')^2}
\sin^2\!\theta_w
\right),
\label{eq:CWgaugebosonmass}
\end{equation}
where $m_Z$ is the SM $Z$ mass.
It is clear from the form of this CW potential that it suffices to require that the correction to the quartic coupling $\lambda_\phi$ should be at most $\lambda_\phi$ itself, as the successive higher order terms are suppressed by powers of $v_0^2 / \Lambda'^2\sim \epsilon^2\ll1$.
Thus, taking into account scale uncertainties, we roughly impose
\begin{equation}
\frac{\lambda_{\phi}}{4!}
\gtrsim
\frac{\sin^2\!\theta_w}{16\pi^2}
\!\left( \frac{m_Z}{\Lambda'} \right)^{\!4}.
\label{eq:CWgauge}
\end{equation}
Using the relation~\eqref{eq:lambda_phi} to eliminate $\lambda_\phi$, this becomes
\begin{align}
\frac{\Lambda'}{\Lambda}
\gtrsim  0.1 \>
\frac{\epsilon}{2.5\times10^{-13} }
\sqrt{\frac{4 \times 10^3\>{\rm keV}^3}{n_{\rm c}}}
\,.\label{eq:gaugebosonloop}
\end{align}
The constraint derived from Eq.~(\ref{eq:gaugebosonloop}) excludes the yellow region in Fig.~\ref{fig:moneyplot}.

Secondly, we  consider corrections due to the $m_e \bar{e} e / \Lambda^2$ term in the tree-level potential~\eqref{eq:Vphi}.
The 1-loop CW potential for $\phi$ from an electron loop is given by
\begin{eqnarray}
\Delta V_e
= -\frac{M_e^4}{8\pi^2} \, \ln{\frac{M_e}{\mu}}
\,,\quad
M_e = m_e \!\left( 1 + \frac{\phi^2}{2\Lambda^2} \right).
\label{eq:CWelectron}
\end{eqnarray}
We see again that it suffices to ensure that corrections to $\phi^4$ are less than $\lambda_\phi$ in the relevant range of $\phi$, because $v_0 / \Lambda  \ll 1$.
This roughly amounts to
\begin{equation}
\frac{\lambda_\phi}{4!}
\gtrsim
\frac{1}{8\pi^2} \!\left(\frac{m_e}{\Lambda} \right)^{\!4}
.\label{eq:CWeconstraint}
\end{equation}
Here, $1 / \Lambda$ is only multiplied by a small mass $m_e$, while $1 / \Lambda'$ is multiplied by a large mass $m_Z$  in the other 1-loop constraint~\eqref{eq:CWgauge}.
Therefore, we could get a stronger constraint on $\Lambda$ from a 2-loop diagram where $1/\Lambda$ comes with a large mass such as $m_{Z/W}$ or $m_h$.
A diagram depicted in Fig.~\ref{fig:e-h-diagram} left, for example, is enhanced by $m_h$.
We estimate the bound from this as
\begin{eqnarray}
\lambda_\phi
\gtrsim
\frac{y_e^2}{16\pi^4}
\!\left(\frac{m_h}{\Lambda}\right)^{\!4}
\sim
\frac{1}{16\pi^4} \frac{m_e^2 m_h^2}{\Lambda^4}
\,,\label{eq:e-h-loop}
\end{eqnarray}
where, to be conservative, we have only kept one power of 16 to account for a possible $O(10)$ numerical factor in the numerator.
This is indeed much stronger than the 1-loop bound~(\ref{eq:CWeconstraint}).
(We also get similar bounds from $Z/W$ exchange instead of $h$.)
Using the relation~\eqref{eq:lambda_phi} to eliminate $\lambda_\phi$, the bound~\eqref{eq:e-h-loop} becomes
\begin{align}
\frac{\Lambda'}{\Lambda}
\lesssim 8 \times 10^6 \>
\frac{2.5\times10^{-13}}{\epsilon}
\sqrt{\frac{n_{\rm c}}{4 \times 10^3\>{\rm keV}^3}}
\,.\label{eq:twoloopconst}
\end{align}
Eq.~(\ref{eq:twoloopconst}) corresponds to the red region in Fig.~\ref{fig:moneyplot}.

\begin{figure}[t!]
 \begin{center}
  \includegraphics[width=0.48\textwidth]{plot3.pdf}
 \end{center}
\caption{
Examples of diagrams contributing to Eq.~\eqref{eq:e-h-loop}~(left) and Eq.~\eqref{eq:fermion}~(right).
}
\label{fig:e-h-diagram}
\end{figure}

In addition to the flatness of the potential, our model also has the property that it is the electron density, not the nucleon density, that controls $\langle \phi \rangle$.
This property is not necessary, and we could repeat the whole analysis for the nucleon case.
For simplicity, however, we require that the electron density plays the dominant role.
Starting from our tree-level Lagrangian~\eqref{eq:Lagrangian},
the operator $\bar{f} f \phi^2$ for fermion $f$ is induced at 1-loop from diagrams like Fig.~\ref{fig:e-h-diagram} right (each $\gamma$ can also be a $Z$).
This is given by
\begin{equation}
\sim \sum_f Q_f^2 \frac{\alpha_{\rm EM}}{\pi} \frac{m_f \bar{f} f}{\Lambda'^2} \frac{\phi^2}{2}
\,,\label{eq:fermion}
\end{equation}
where $m_f$ and $Q_f$ are the mass and electric charge of fermion $f$.
When $f$ is a light quark $q = u$, $d$, or $s$, the contribution from the QCD condensate, $m_q \langle \bar{q} q \rangle \sim m_\pi^2 f_\pi^2$, is absorbed in $\mu_\phi^2$,
and the contributions from nucleons can be estimated by replacing $m_q \bar{q} q$ by $m_N \bar{N} N$ for nucleon $N$.
Since $(\alpha_{\rm EM} / \pi) m_N / m_e \sim 4$,
the requirement that the $m_e \bar{e} e / \Lambda^2$ operator should control $\langle \phi \rangle$ amounts to $\Lambda' \gtrsim$ a few$\times\Lambda$,
which is already stronger than the condition~\eqref{eq:gaugebosonloop},
but to be conservative we impose (shown by the dashed brown line in Fig.~\ref{fig:moneyplot})
\begin{equation}
\Lambda'\gtrsim 10\Lambda \,.
\label{eq:nucleon}
\end{equation}
Although this is not strictly necessary as we stated above,
this and the bound~\eqref{eq:twoloopconst} provides the strongest conditions on the self-consistency of our analysis:
\begin{equation}
10 \lesssim \frac{\Lambda'}{\Lambda} \lesssim 8\times10^{6}\;.
\end{equation}
Other potential constraints we checked such as top loop contributions and a radiatively generated $\phi^2 H^\dag H$ interaction do not impose additional restrictions on the parameter space.
We thus see a large parameter space in which quantum corrections do not destroy the flat potential (as well as the dominant role of the electron density).

\section{UV completion}
\label{sec:UV}

\subsection{General estimates of scales}
We begin by a general discussion that new degrees of freedom that UV-completes the EFT should appear roughly at the TeV scale.

Let $M'$ be a representative mass scale of new particles in the UV theory responsible for generating the $\phi B^{\mu\nu} F'_{\mu\nu}$ operator of the EFT\@.
To generate this operator,
the UV theory must contain an interaction linear in $\phi$.
Let $y'$ be the dimensionless coupling constant of that interaction (measured in units of $M'$ if it is dimensionful).
Then, roughly, we have
\begin{align}
    \frac{1}{\Lambda'} \sim \frac{g' g_Y}{4\pi^2} \frac{y'}{M'}
    \,,\label{eq:rough:matching:M'}
\end{align}
where $g'$ and $g_Y$ are the U(1)$_{A'}$ and U(1)$_Y$ gauge couplings, respectively,
and we have imagined a typical 1-loop factor, $(\text{several})/16\pi^2$.
(We will later see why it must be at 1-loop.)
On the other hand, using the same $y'$ vertex 4 times, we also generate a correction to the $\phi^4$ operator.
In order to avoid fine tuning in $\lambda_\phi$ upon matching the UV theory to the EFT, we must roughly impose
\begin{align}
    \frac{y'^4}{4\pi^2} \lesssim \lambda_\phi
    \,.\label{eq:rough:no-tuning}
\end{align}
Since we know that $\lambda_\phi$ is extremely tiny, this shows that $y'$ must also be very small.
Then, in the relation~\eqref{eq:rough:matching:M'},
we see that $M$ can be at quite a low scale despite the fact that $\Lambda'$ is very high.
To proceed more concretely, we eliminate $\lambda_\phi$ in the condition~\eqref{eq:rough:no-tuning} by using the relation~\eqref{eq:lambda_phi} with $\epsilon = 2.5 \times 10^{-13}$ and $n_{\rm c} = 4 \times 10^3\>{\rm keV}$.
This gives
\begin{align}
    y' \lesssim \frac{O(10^2)\>{\rm GeV}}{\sqrt{\Lambda\Lambda'}}
    \,.\label{eq:rough:y}
\end{align}
Applying this inequality to the matching relation~\eqref{eq:rough:matching:M'}, we get
\begin{align}
    M' \lesssim O(10^2) \, g' \sqrt{\frac{\Lambda' / \Lambda}{10^4}} \>{\rm GeV}
    \,,\label{eq:rough:M':Lambda-Lambda'}
\end{align}
where, from Fig.~\ref{fig:moneyplot}, the maximum possible value of $\Lambda' / \Lambda$ is roughly $O(10^4)$ in a large portion of the allowed region.

Let us do similar general estimates for the UV completion of the electron density dependent operator in~\eqref{eq:Vphi}.
Let $M$ be a representative mass scale of new particles responsible for generating the density dependent operator,
and $y$ be a representative size of the couplings of $\phi$ to those particles, defined such that each $\phi$ comes with one $y$
(that is, if the interaction is $\propto \phi^n$, its coefficient is  $\propto y^n$ by definition.)
Then, upon integrating out the new particles at $M$, we have
\begin{align}
    \frac{y_e}{\Lambda^2} = \frac{c y^2}{M^2}
\,,\label{eq:rough:matching:M}
\end{align}
where $c$ represents all other coupling constants and numerical factors in the diagram and, if not at tree level, loop factors.
As we estimated above for $y'$,
avoiding fine tuning in $\lambda_\phi$ roughly requires
$y \lesssim O(10^2) \>{\rm GeV} / \sqrt{\Lambda\Lambda'}$.
Using this with the matching condition~\eqref{eq:rough:matching:M},
we get
\begin{align}
    M \lesssim O(10^3)\>{\rm GeV} \> \sqrt{c} \, \sqrt{\frac{10^4}{\Lambda'/ \Lambda}}
\,.\label{eq:rough:M:Lambda-Lambda'}
\end{align}
Both~\eqref{eq:rough:M':Lambda-Lambda'} and~\eqref{eq:rough:M:Lambda-Lambda'} point to a sub TeV scale for $M'$ and $M$, provided that $g' \sim c \sim O(1)$.

The existence of new particles with roughly sub-TeV masses is a {\it prediction} implied by the allowed region of the EFT parameters.
Eq.~\eqref{eq:rough:M':Lambda-Lambda'} tells us that we must have $g ' \sim O(1)$ in order for the new particles at $M'$ not to have already been experimentally excluded, since they carry hypercharge to generate the $\phi B^{\mu\nu} F'_{\mu\nu}$ operator.
Therefore, it is guaranteed that we will have new electrically charged particles with sub-TeV masses with $O(1)$ couplings to the dark photon.
Moreover, the $\phi B^{\mu\nu} F'_{\mu\nu}$ operator should not be generated at a higher loop order than one as that would lower $M'$ too much.
This means the new particles at $M'$ must couple to $\phi$ at tree level,
albeit with tiny couplings.
Similarly, in order for the new particles at $M$ not to be too light, they must generate the density dependent operator at tree level with all couplings except $y$ being $O(1)$ so that $c \sim O(1)$.

Therefore, from the general estimates, we already see the opportunity to experimentally probe our scenario further with a window into the dark sector for laboratory experiments.
We also see that the structure of any explicit model of the UV completion is very constrained.

\subsection{An explicit UV model}
Now that it is testable experimentally, it is worth building an explicit example of the UV completion.
Conceptually, we must also address the UV origin of the $Z_2$ symmetry~\eqref{eq:Z_2}, which we call $Z_2^{A'}$,
so let us begin with this.
Since $A'$ is odd under $Z_2^{A'}$ while all SM gauge fields are even,
$Z_2^{A'}$ must act as charge conjugation for U(1)$_{A'}$
while it must not for the SM gauge group.
The simplest possibility, therefore, is to introduce two new heavy particles $\psi_{1,2}$ exchanged by $Z_2^{A'}$ with opposite U(1)$_{A'}$ charges and the same SM charges. The SM charges must at least include a nonzero hypercharge to generate the $\phi B^{\mu\nu} F'_{\mu\nu}$ operator.
For simplicity and definiteness, we take $\psi_{1,2}$ to be Dirac fermions with $M'$, $Y_\psi$, and $\pm g'$ being their common mass, hypercharge, and the opposite U(1)$_{A'}$ charges, respectively.
For $\phi$, we have $\phi \to -\phi$ under $Z_2^{A'}$ in the UV just as in the EFT\@.

Now the UV degrees of freedom and symmetries have been fixed.%
\footnote{If cosmological domain walls from the $Z_2^{A'}$ breaking become a problem, we can softly break $Z_2^{A'}$ by introducing a small mass splitting between $\psi_1$ and $\psi_2$.
This will induce a bare kinetic mixing between $B_{\mu\nu}$ and $F'_{\mu\nu}$, which must be smaller than the $10^{-15}$ level (see Fig.~\ref{fig:bestfit}).}
Gauge symmetries and $Z_2^{A'}$ allow just one coupling between $\psi_{1,2}$ and $\phi$:
\begin{align}
{\cal L} \supset -y' \, \phi (\bar{\psi_1} \psi_1 - \bar{\psi_2} \psi_2)
\,.\label{eq:y'_Yukawa}
\end{align}
Thus, the new particles $\psi_{1,2}$ couple to $\phi$ at tree level as required by the general analysis above.
This is another reason why we need at least two new degrees of freedom to realize $Z_2^{A'}$.
If we just had one $\psi$ and conjugate $\psi$ itself under $Z_2^{A'}$, we would not be able to couple it to $\phi$.

Accidentally, this UV model can also offer a WIMP DM candidate if $\psi_{1,2}$ contain an electrically neutral state, because the Lagrangian has an accidental U(1)$_{\psi_1}\times$U(1)$_{\psi_2}$ global symmetry, which ensures the neutral state to be stable if it is the lightest.

The $\phi B^{\mu\nu} F'_{\mu\nu}$ operator is generated at 1-loop from $\psi_{1,2}$ loops (see Fig.~\ref{fig:Lambda'diagram}).
We find
\begin{align}
\frac{1}{\Lambda'} = \frac{y' g' Y_\psi g_Y^{\phantom*}}{3\pi^2 M'}
\,.\label{eq:matching_Lambda'}
\end{align}
Then, following the steps that led to the bounds~\eqref{eq:rough:M':Lambda-Lambda'}
with more precise numerical coefficients for this model,
we find
\begin{align}
M' \lesssim 2 \times 10^2\>{\rm GeV} \>  g' Y_\psi \sqrt{\frac{\Lambda' / \Lambda}{10^4}}
\!\left( \frac{n_{\rm c}}{4 \times 10^3\>{\rm keV}^3} \right)^{\!1/4}
\,.\label{eq:Mpsi}
\end{align}
It should be emphasized that  this inequality is still rough as it comes from the condition not to fine-tune $\lambda_\phi$ against quantum corrections, which is not a quantitatively sharp criterion.
Moreover, the right-hand side above will be enhanced by a factor of $N^{3/4}$ if there are $N$ pairs of $\psi_{1,2}$,
which is natural if $\psi_i$ forms a multiplet under some other symmetry such as SU(2)$_W$.

\begin{figure}[t!]
 \begin{center}
  \includegraphics[width=0.3\textwidth]{plot4.pdf}
 \end{center}
 \vspace{-10pt}
\caption{Diagrams contributing to Eq.~\eqref{eq:matching_Lambda'}.}
\label{fig:Lambda'diagram}
\end{figure}

Let us now explicitly UV complete the electron density dependent operator.
The aforementioned requirement of generating the operator at tree level via $O(1)$ couplings to the electron and/or Higgs
strongly suggests vectorlike leptons with Yukawa couplings to $\phi$.
A minimal possibility is to consider two vector-like pairs of leptons, $L_{\rm L, R}$ and $E_{\rm L, R}$, with masses $M_L$ and $M_E$, respectively.
All of these are neutral under U(1)$_{A'}$,
and they are all odd under $Z_2^{A'}$.
Writing down all gauge and $Z_2^{A'}$ invariant renormalizable interactions, we have
\begin{align}
{\cal L}
\supset&\>
-y_E^{\phantom*} H \bar L_{\rm L}  E_{\rm R}
- y_E' H \bar L_{\rm R} E_{\rm L}
- y_1 \, \phi \bar \ell_{\rm L} L_{\rm R} - y_2 \, \phi \bar e_{\rm R} E_{\rm L}
\nonumber\\
&\>+ \text{h.c.}
\,,\label{eq:vectorlike}
\end{align}
where $\ell_{\rm L}$ and $e_{\rm R}$ are the SM lepton fields.
Integrating out the vector-like leptons at tree level, we find
\begin{eqnarray}
\frac{y_e}{\Lambda^2}
= \frac{2y_E^{\phantom*} y_1 y_2^*}{M_L M_E}
\,.\label{eq:matching1}
\end{eqnarray}
Therefore, $c = 2y_E^{\phantom*}$, $y = \sqrt{y_1 y_2^*}$, and $M = \sqrt{M_L M_E}$ in Eq.~\eqref{eq:rough:matching:M}.
Upon integrating out $L$ and $E$, corrections to $\lambda_\phi$ is given by
\begin{align}
\Delta \lambda_\phi
= -\frac{3}{2\pi^2}
   \!\left( 2|y_1|^4 \ln\frac{M_L}{\mu}
           +|y_2|^4 \ln\frac{M_E}{\mu}
    \right),
\end{align}
up to scheme dependent finite terms.
So, our estimate~\eqref{eq:rough:M:Lambda-Lambda'} is now refined as
\begin{align}
\sqrt{M_L M_E} \lesssim 1\>{\rm TeV} \> \sqrt{y_E^{\phantom*}} \, \sqrt{\frac{10^4}{\Lambda' / \Lambda}}
\!\left( \frac{n_{\rm c}}{4 \times 10^3\>{\rm keV}^3} \right)^{\!1/4}
\,.\label{eq:M:Lambda-Lambda'}
\end{align}
Thus, this can be experimentally probed as well.
Unlike the guaranteed existence of new hypercharged particles at $M'$,
however, the vectorlike leptons may not be a unique possibility.
For example, it may be possible that the new particles at $M$ carry no SM charges,
e.g., via some kind of a Higgs portal.
Also, a viable range of $\Lambda' / \Lambda$ is small in the simple example construction above,
which could become larger for a complicated model with multiple hierarchical scales and couplings.
But such model building exercises are beyond the scope of our present work.

The simple UV model above offers rich experimental probes.
First, electroweak/Higgs precision tests place severe constraints on a vector-like lepton~\cite{Ellis:2014dza}, which tends to push the mass beyond the LHC reach~\cite{Kumar:2015tna, Aaboud:2019trc,Khachatryan:2016sfv}.
However, if the flavor/CP structures of the Yukawa couplings~\eqref{eq:vectorlike} are generic,
the vector-like-lepton sector can be indirectly tested through lepton flavor violation, such as $\mu \to e\gamma$ and $\mu\to eee$~\cite{Papa:2020umc}, as well as the electric dipole moment of the electron~\cite{Andreev:2018ayy}.

On the other hand, $\psi_i$ ($i=1,2$) can be produced at the LHC because the mass scale is expected to be a few hundred GeV as in~\eqref{eq:Mpsi}.
They can be constrained by searches for heavy charged states~\cite{Aaboud:2019trc,Khachatryan:2016sfv}.
The bound can be relaxed if $\psi_i$ is a weak multiplet containing a neutral state $\psi_i^0$ (e.g., a weak doublet (triplet) with $Y_\psi = 1/2$ ($Y_\psi=1$)),
which will allow weak decays of the charged states, e.g., $\psi_i^\pm \to \psi_i^0 \pi^\pm$.
The neutral states $\psi_i^0$ can be a WIMP dark matter candidate as they are stable thanks to the accidental U(1)$_{\psi_1}\times$U(1)$_{\psi_2}$ symmetry mentioned below~\eqref{eq:y'_Yukawa}.
In this case, searches for disappearing tracks will be relevant (e.g.~\cite{Sirunyan:2020pjd, ATL-PHYS-PUB-2019-011}).
Detailed phenomenologies are UV model specific and beyond the scope of the present paper.

\section{Comparisons with other similar scenarios}
\label{sec:difficulties}
The key idea of our dark photon model is that the kinetic mixing parameter is density-dependent.
Similar ideas may be applied in different ways.
For example, one might consider a density dependent mass instead of coupling.
Or, as originally discussed in Refs.\,\cite{Bloch:2020uzh, DeRocco:2020xdt}, an axion-like particle (ALP) may be the signal particle corresponding to the XENON1T excess.
In the following, we would like to discuss various other scenarios, including both new and existing proposals, and point out difficulties that arise in each case to highlight the success of the dark photon model.

\subsection{Alternative dark photon scenarios}
The most obvious alternative to our dark photon scenario of Sec.~\ref{sec:dark} would be the following.
In Fig.~\ref{fig:bestfit}, instead of going down by turning off $\epsilon$ in dense stars, going far to the left by turning off $m_{A'}$ in dense stars could also evade the HB/RG bounds.
It is straightforward to modify the Lagrangian~\eqref{eq:Lagrangian} to realize this alternative.
We just need to do two replacements:
(i) replace the $\phi B^{\mu\nu} F'_{\mu\nu}$ interaction by a bare kinetic mixing term $\epsilon B^{\mu\nu} F'_{\mu\nu}$ with a {\it fixed} mixing parameter $\epsilon = 2.5 \times 10^{-13}$,
and (ii) replace the real scalar $\phi$ by a complex scalar $\Phi$ charged under U(1)$_{A'}$, and delete the St\"uckelberg mass term for $A'$.
Then, denoting the U(1)$_{A'}$ gauge coupling by $g'$,
we would have $m_{A'} = g'\langle\Phi\rangle = 2.3\>{\rm keV}$ in the vacuum/sun while $m_{A'} = 0$ in HB/RG stars.
This would be a simpler theory as it introduces only one non-renormalizable operator, $m_e \bar{e} e |\Phi|^2 / \Lambda^2$, rather than two.

It does not work, however.
Essentially, the problem is that, unlike $\phi$ in the model of Sec.~\ref{sec:dark}, $\Phi$ here is charged under U(1)$_{A'}$.
The CW potential from $A'$ loop can then more directly impact the flatness of the $\Phi$ potential here than in the $\phi$ case.
If we decrease $g'$ to mitigate the impact,
we would have to increase $\langle \Phi \rangle$ to keep $m_{A'}$ fixed in the vacuum/sun, which, however, would require an even more flat potential.
While the model still passes all 1-loop tests, it does not survive through the 2-loop diagrams discussed around Eq.~\eqref{eq:e-h-loop}.
Here, Eq.~\eqref{eq:e-h-loop} should be adapted as follows.
The scale $\Lambda$ can be eliminated in favor of $v_0$ and $\lambda_\phi$ via $\lambda_\phi v_0^2 \sim m_e n_{\rm c} / \Lambda^2$, where $v_0$ can be further expressed as $v_0 = m_{A'} / g'$.
The modified Eq.~\eqref{eq:e-h-loop} now roughly reads $g'^4 / \lambda_\phi \gtrsim (m_h m_{A'}^2 / n_{\rm c})^2 / (16\pi^4) \sim 10^7$ for $m_{A'} \sim 2\>{\rm keV}$ and $n_{\rm c} \sim 10^3\>{\rm keV}^3$.
But this contradicts with the condition $g'^4 / \lambda_\phi \lesssim 1$ to ensure the 1-loop CW potential from $A'$ loop not to destroy the flat potential.

The same reason also excludes yet another dark photon scenario in which $m_{A'}$ {\it increases} in dense stars instead of decreasing.
This is the same model as above except that the sign of the $\bar{e} e |\Phi|^2 / \Lambda$ term is flipped so that U(1)$_{A'}$ is more broken in denser stars than in the vacuum/sun.
Since the estimates above never relied on the sign of this term, this alternative is also unattainable due to too large quantum corrections.
We thus conclude that, at least among the simplest dark photon models, our scenario of Sec.~\ref{sec:dark} seems the only viable option.

\subsection{Density depedent ALP models}
We now consider the case when an ALP gives the XENON1T signal instead of a dark photon.
In this case, we have two directions for utilizing the density dependence: suppressing ALP couplings or increasing the ALP mass in dense stars.

Let us begin by the idea of suppressing ALP couplings.
In the ``chameleon-like'' ALP model of Ref.~\cite{Bloch:2020uzh}, there is an operator, $c_{ee} m_e \bar{e} e XS / M^2$, where $X$ and $S$ are respectively real and complex scalars, both of them being odd under a $Z_2$ symmetry.
The ALP, $a$, comes from $S \sim (f_a + s) \, {\rm e}^{{\rm i} a / f_a}$.
The potential $V(X)$ is identical to our potential $V(\phi)$ in~\eqref{eq:Vphi} with the replacements of $\phi$ and $m_e \bar{e} e / \Lambda^2$ by $X$ and $\rho / M^2$, respectively, where $\rho$ is the {\it energy} density as opposed to the number density.
Thus, in dense stars $\langle X \rangle$ vanishes and eliminates the stellar cooling problem due to ALP production.

Unfortunately, as it is already discussed in Ref.~\cite{Bloch:2020uzh}, the flatness of the potential suffers from too large quantum corrections.
In addition, since $\rho$ appears in a quantum field theory Lagrangian, we interpret it as arising as the expectation value of a dynamical operator such as $m_e \bar{e} e$, $m_N \bar{N} N$ or ${\rm tr}[G_{\mu\nu} G^{\mu\nu}]$, where $N$ and $G$ are a nucleon and the gluon field, respectively.
Then, there are additional loops from, e.g., a gluon loop or two-loop diagrams as in Fig.~\ref{fig:e-h-diagram} left.
We also find that the  $c_{ee}$ operator  generates a tadpole term of $X$ in dense stars proportional to $n_e$ which prevents $\langle X \rangle$ from vanishing.
These effects could lead to even stronger constraints on the potential.

We now switch to the idea of increasing the ALP mass.
In Ref.\,\cite{DeRocco:2020xdt}, the ALP mass increases in dense stars as $\langle \phi \rangle$
and its production is kinematically forbidden
when the mass becomes heavier than the core temperature of the star.
The ALP is the ``pion'' of a dark QCD, where the dark quark masses are proportional to $\langle \phi \rangle^2$ via a see-saw with a heavy fermion.
A nonzero $\langle \phi \rangle$ arises from a tadpole due to a Yukawa interaction $\phi \bar{N} N$ when the nucleon density $\bar{N} N$ is turned on.

Ref.\,\cite{DeRocco:2020xdt} already mentions fine tuning issues in some parameters in the dark sector.
Here, to relate to our earlier discussions, let us look at 1-loop quantum corrections to the $\phi$ potential.
In particular, the see-saw requires Yukawa couplings of $\phi$ to a light dark quark and a heavy dark quark,
which then contribute to the 1-loop CW potential from dark quark loops,
where the coefficient of $\phi^{2n}$ is roughly given by $y^{2n} M^{4-2n}/16\pi^2$.
Requiring the generated $\phi^{2n}$ term to be smaller than the tree-level $\lambda \phi^4$ for $\phi \sim \langle \phi \rangle$,
we have $y^{2n} (\langle \phi \rangle / M)^{2n-4}/16\pi^2 \lesssim \lambda$.
In the benchmark model of Ref.\,\cite{DeRocco:2020xdt},
we have $\lambda = 10^{-78}$, $y = \sqrt{g_1 g_2} = 3 \times 10^{-11}$, $M = 30\,{\rm TeV}$,
and $\langle \phi \rangle \simeq 3 \times 10^{12} \, m_a$
with $m_a \simeq 7\>{\rm MeV}$ in white dwarfs.
With these values, the potential needs to be fine-tuned up to and including $\phi^{10}$.

As our final example, we consider a scenario where the ALP coupling to the electron is proportional to $1 / \langle \phi \rangle$,
where $\langle \phi \rangle$ increase in dense stars to suppress the ALP production.
This can be realized in a DFSZ-like model of the axion~\cite{Dine:1981rt, Zhitnitsky:1980tq} where $\langle\phi\rangle$ breaks the Pecci-Quinn (PQ) symmetry
in a density dependent way as in~\eqref{eq:Vphi} but with the sign of the $\Lambda^2$ term being flipped.
Provided that $\langle \phi \rangle$ in the vacuum, $v_0$, is much larger than the electroweak symmetry breaking scale,
the coupling of the axion to the electron is given by
$(m_e / v_0) \, a \bar{e} \gamma_5 e$.
Then, from the value of $g_{aee}$ in Ref.~\cite{Aprile:2020tmw}, we get $v_0\sim 10^9\,{\rm GeV}$.

Now, the cutoff $\Lambda$ of the effective theory provides the maximum possible value of $\langle \phi \rangle$ in a dense environment.
The validity of the theory in white dwarfs, where the electron density is $10^4$ higher than in the sun, requires $\Lambda \gtrsim 10^2\,v_0 \sim 10^{11}\,{\rm GeV}$.
Such large $\Lambda$ forces $\mu_\phi \lesssim 10^{-11}\,{\rm eV}$.
The large hierarchy between $m_\phi$ and $v_0$ requires a tiny quartic coupling $\lambda_\phi \sim \mu_\phi^2 / v_0^2 \lesssim 10^{-58}$.
But the theory needs an interaction of the form $c \phi^2 H_1 H_2$ to identify the global U(1) carried by $\phi$ as the U(1)$_\text{PQ}$ carried by the two Higgs doublets (and, therefore, the SM fermions).
This operator radiatively corrects $\lambda_\phi$, which is roughly  $c^2/16\pi^2$. But one of the CP-odd scalars, $A$, has a mass $m_A \sim  \sqrt{c} v_0$. Requiring $m_A \gtrsim 100\>{\rm GeV}$, we have $c \gtrsim 10^{-14}$, but this implies the above correction to $\lambda_\phi$ is at least $\sim 10^{-30}$, which is $\gg 10^{-58}$.
Thus, again, the model suffers from too large quantum corrections.

To conclude, it appears to be generic that an extremely flat potential is needed to explain the XENON1T excess while evading the stellar cooling problems in denser stars by a density-dependent vev of a scalar field.
What we have seen in the examples above is that it is not easy to maintain the flatness of the potential at quantum level.
Therefore, it is quite nontrivial that our dark photon model has a large region in the parameter space where the potential receives no large quantum corrections (except for the mass terms, of course).

\section{Summary}
We have shown that a solar dark photon with a density-dependent kinetic mixing with the photon could explain the XENON1T signal excess while avoiding bounds from stellar cooling.
We have provided an explicit effective Lagrangian in which the kinetic mixing is proportional to the expectation value of a scalar field $\phi$ with an electron density dependent potential.
The kinetic mixing vanishes in dense stars, permitting the model to evade stellar cooling bounds, while acquires a nonzero value in the sun/vacuum, providing the signal strength and shape to explain the XENON1T excess.

We have studied both phenomenological and theoretical constraints.
We have found that stellar cooling due to $\phi$-pair and $\phi$-$A'$ productions provides the lower bounds on the scales $\Lambda$ and $\Lambda'$ of the effective theory.
As these bounds imply an extremely flat potential of $\phi$,
we have studied the impact of radiative corrections on the flatness.
This leads to strong lower and upper bounds on the ratio of $\Lambda'$ to $\Lambda$.
All these phenomenological and theoretical constraints are summarized in Fig.\,\ref{fig:moneyplot}.
We emphasize that having a large allowed parameter space is quite nontrivial without fine tuning against quantum corrections.

We have presented a general argument that the scales in our effective theory predicts new electrically charged particles with roughly sub-TeV masses in the UV completion.
Our scenario is thus testable via laboratory experiments such as lepton flavor/CP violation measurements, electroweak/Higgs precision tests, and colliders.
We have constructed a simple explicit example of the UV completion in terms of fermions charged under $U(1)_Y\times U(1)_{A'}$ and vectorlike leptons.
This simple model can contain a dark matter candidate and provide a rich collider phenomenology with displaced vertices and disappearing tracks.

{\it Note Added---}
In the final stage of writing this paper, new work on the solar dark photon \cite{Lasenby:2020goo} appeared. If there is an additional flux of dark photons as pointed out in Ref~\cite{Lasenby:2020goo}, the best fit point of the kinetic mixing for the XENON1T excess will decrease from the current benchmark $\epsilon\simeq 2.5\times10^{-13}$ to $\epsilon\sim 10^{-14}$. This will still be in tension with the cooling bounds by HB/RG stars. Therefore, the main points of our paper will be unchanged.

\section*{Acknowledgment}
This work is supported by the US Department of Energy grant DE-SC0010102.
KT thanks to Natsumi Nagata, Kazunori Nakayama, Kenichi Saikawa, and Diego Redigolo for useful discussions.

\bibliographystyle{utphys}

redpajama_set_name: RedPajamaArXiv


Notice each synthesis from the above examples: Relativism, Neo-Progressivism, Corporatism, Ecumenism; all are precise objectives on the menu for the power-elite.
Within this process, conflict and chaos are created at great cost of lives and resources to dismantle the social and political structures by which free societies govern themselves; ultimately to be replaced with centralized power and control of the people and resources.
Such a strategic agenda is the real cause of so many of the shootings, bombings, economic crises, wars, revolutions, etc, etc. It's time to wake up and recognize the strategies being used against us. This is a high call for keen discernment.
'Hegelian Dialectics' is a key component of the Luciferian system, which is not just a religious system, but a political system; the Hegelian principle is summed-up in their creed "Ordo Ab Chao" (Order from Chaos).
Such methodology has been highly effective for the elite-ruling class (namely the high ranking Jesuits, who leverage a whole host of different religious and political powers to gain greater dominance.
Order from chaos works like this: "Chaos", for one, distracts the population to "pay no attention to the man behind the curtain", and two, causes the people to get so tired of the conflict that they are willing to compromise almost anything for some harmony.
That harmony then comes in the "Order" of those who (secretly) caused the problem- so they can implement their "solution" which is promoted to be in the best interest of the commonwealth of the people, but in actuality, is impoverishing and enslaving them.
Hegelian Dialectics is as old as politics, but took on a whole new dimension to counter the Protestant Reformation through the military arm of The Jesuit Order. The Jesuits were recognized for causing so much chaos (revolutions, wars, assassinations) that they were expelled from almost every nation in Europe by the mid 1700's.
When making their comeback and complete takeover of the Vatican in the early 1800's, the Jesuits were prepared to be virtually undetectable as they mastered the arts of espionage and infiltration strategies; And as a result of their great success, most have no idea what the Jesuits are really about- how devious and diabolical they really are, as well as the vast amount of global temporal power they have secured.
And with such power and control, they easily have the means to rewrite history to cover their conspiracies, while painting a nicer picture of their image and track record..
As mentioned, this dialectic principle was brought to a whole new dimension by the Jesuit Order, who were commissioned by the Pope to combat the Protestant Reformation. Most people only recognize the mayhem of the Counter-Reformation and it's so-called "Holy Inquisition" as something that we are now hundreds of years removed from.
Most people know of the tens of millions of people mass murdered by Stalin, but a detail most folks are not aware of, is that most of those people were various kinds of Christians such as Orthodox & Protestants.
Most people know of the six million Jews that were killed under Hitler's Third Reich, but most are not aware of the 13 million Protestants who were annihilated, mostly from Northern Germany, who were fire-bombed, not by Hitler, but by the Allies, under the assumption and propaganda that states like Prussia were in cahoots with the SS.
Most people have no idea that these cruel dictators like Stalin, Hitler, Pavelic, Musilini and many more were commissioned by the Catholic Hierarchy as modern day Inquisitors of the ongoing Counter-Reformation. And what's even more difficult for Americans to see and accept is how the US has been leveraged for the same purposes.
When understanding the stratagem of the Hegelian principle, you can then begin to recognize how it was implemented throughout history; And after recognizing this element in history, you can then recognize it in our present time. If you wish to cut through the lies and deception to see what the actual truth is, then it is of the essence to not only know the Truth of God's Word and Spirit, but to understand the workings of Satan's worldly system.
It's also very important to know that this satanic system has launched major disinformation campaigns as well as history revision campaigns, within this past century, to cover-up the true nature and magnitude of such atrocities. Many books, people and other sources that have documented the true accounts have been destroyed or suppressed, and replaced with false versions of such accounts.
Daniel's Dream – What Does it Mean?


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Album Review: In Small Hours
Matthew Labarge
Matthew's Website Matthew's Artist Page on MainlyPiano
iTunesAmazon (referral)
In Small Hours
2007 / Cynelic Gast Music
In Small Hours, a concept album that starts with the descent of evening and gradually moves through the night, is Matthew Labarge's follow-up to his 2002 debut, "First Fall Night." The piano solos on In Small Hours are deeper and more sophisticated than on the first album, and also vary from slow and quiet to more upbeat and vibrant. Using night as an analogy for winter, the album could also follow early winter into the dawn of spring. The recording was engineered and co-produced by Grammy Award-winning engineer Corin Nelsen at Will Ackerman's Imaginary Road Studio (played on Ackerman's magical piano!), and was mastered by Bob Ludwig at Gateway Mastering, so the sound quality approaches perfection. Ranging in length from thirty-six seconds to almost six minutes, the music is mostly peaceful and melodic, but there are a few pieces where the tempo and energy are increased substantially. Labarge's playing is elegant and expressive, demonstrating his considerable classical training. The concept of the album came from years of Labarge listening to his mother play, mostly for friends who would drop by the family home when the boys were supposed to be asleep. Labarge would sneak out of his room and listen intently, amazed at the colors and moods created via the piano, inspiring him to pursue his own piano studies.
In Small Hours begins with "Evening Descends," which is based on the 16th century melody for the hymn, "We Gather Together." Played at a relaxed and easy tempo, this familiar piece sounds quite contemporary and new. "Solace 1" is soothing grace set to music, perhaps representing the peace and calm of being at home with loved ones after a long day. "Rhapsody (Moonrise)" is gorgeous! Graceful, elegant, and very passionate, a snippet of "O Holy Night" is seamlessly woven into Labarge's own melody. "Solace 2" is an abstract, somewhat discordant little vignette that serves as a bridge to "Prelude (Snowing)," which begins darkly and quietly, but has a light, sparkling passage that suggests moonlight on the snow. "Song (Nocturne)" is another brief, freeform piece that changes the scene a bit. "Song (I Can't Believe I'm the Only One)" has a warm, joyful melody that seems perfectly suited for lyrics. I hear a little bit of James Taylor in this one! "Waltz" is a minor key beauty, graceful and melancholy. "Fantasy" picks up the pace considerably, staying dark and mysterious as it demonstrates Labarge's considerable piano chops. "Barcarolle (In Small Hours)" goes even darker and deeper - a bit of a nightmare or memories that bring a chill - very effective! "Always Eventually Daybreak" swings the mood back to optimism and a feeling of relief and redemption. "Joyfully" almost leaps out of the CD player as a new day or new spring arrives and everything is fresh and new again. "Peace" follows as the day/season warms - a very quiet, serene piece that brings a sigh of contentment. "Love Song" concludes the night/winter journey with a warm hug.
In Small Hours is a very impressive CD. Five years in the making, the music shows Matthew Labarge's versatility as a composer and pianist, and should establish him as a major artist in the contemporary piano realm. First issues of the CD include a bonus twelve-minute CD called Five Midnights, which is electronic with some percussion. This CD is available from matthewlabarge.com, amazon.com, cdbaby.com, and iTunes. Highly recommended!
More reviews of Matthew Labarge albums
Music From the Long Quiet
Kathy's Picks

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Janet Zaretsky, aka The BS-to-Brilliance Master, is a master professional coach, author, and speaker that helps people unleash their brilliance, confidence and visibility in the world. A powerful advocate for ending the gender gap, both in pay and influence, hasn has led her to be a frequent contributor to Forbes and the author of "Where'd My Confidence Go… and how do I get it back?". A two-time TEDX and Keynote Speaker, a corporate trainer and expert in communication and leadership, an International Coach Federation member, Enhanced Conversational Intelligence Coach, Certified in Behavioral Style Instruments, graduate of Coach U, former senior program leader for Landmark Worldwide.


Nowadays, it's all about the 'gram. I've taken the liberty to look up Ontario's most instagrammable places where you're guaranteed to get the best pictures. Now, I just need to get to every place on my list. Follow along as I share with you the big cities, the small towns, grand landscapes and more! There is a reason to love every city, every corner and every park.


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David is the man!! Love watching this guy. Keep rockin' David.
David Lee has incredible stage presence. Beyond playing the guitar, this kid puts on a show.
David is eight years old. He has been playing guitar since age 4. By age 5 David began playing and singing in front of live audiences. He wrote an original song at age 6 and donated the recording to Rex Fest Foundation, a charity benefiting families with Down Syndrome. He performs live sets on his own and with his music school.


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HEALTH & FITNESS >
Alternative Therapies >
Writing Away the Demons
David Read Johnson and Sherry Reiter
About David Read Johnson
About Sherry Reiter
Sherry Reiter, PhD, director of The Creative "Righting" Center, is a licensed clinical social worker (LCSW), a registered poetry therapist (PTR-M/S), and registered drama therapist (RDT-BCT). Dr. Reiter entwines talk therapy with writing therapy; poetry, story, and the reclaiming of voice are dynamic healing components in her work. Sherry divides her time between writing, teaching at Touro College and Hofstra University, and private practice. At The Creative "Righting" Center, she mentors helping professionals who want to incorporate creative techniques into their work. Sherry is the coordinator of Poets-Behind-Bars, an innovative long-distance training program, in which poetry therapy trainees mentor inmates of the Indiana State Maximum Security Prison. Dr. Reiter served as president of the National Association for Poetry Therapy (1993-1995), and was president of the National Federation for Biblio/Poetry Therapy (1995-2005). She is the recipient of the Art Lerner Pioneer Award (2005), and the Morris Morrison Education Award (2007) for excellence in teaching and bringing poetry to marginalized populations. Sherry aspires to the beautiful words of poet Dawna Markova: to live so that which comes to us as seed / goes to the next as blossom / and that which comes to us as blossom / goes on as fruit.
HEA032000 (HEALTH & FITNESS / Alternative Therapies)
Interrupted Lives
by Krugerud, Mary
This is the history both of Tuberculosis in Minnesota and of the Glen Lake Sanitorium, where, in the first half of the twentieth century, so many TB patients were housed as they fought their illness...
Song of Destiny
by Legler, Paul
Jake was the ultimate big brother: cool, suave with the girls, tough, and a Vietnam veteran. Peter, the younger brother, was always the "good kid," eventually becoming a monk at St. John's Abbey. But they came of age on the North Dakota plains at a time when sex, drugs, and rock & roll blasted onto the prairie. Thirty years later, neither brother can escape his past.


When using multiple aerodynamic products it is important to consider how well they work together. The Trailer AeroSlider works in tandem with side skirts or tails to smooth the airflow across the trailer wheels.
Measure the spacing between the two holes on the trailing arm frame bracket from centerpoint to centerpoint.
Measure the distance between the outside edges of the trailer suspension frame rails.


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By Admin2 on June 2, 2016 in
Revision for "Stamford" created on September 7, 2017 @ 00:10:29
Find a Podiatrist in Stamford, Connecticut:

 Stamford is a city in the county of Fairfield in the state of Connecticut. The most recent census puts the population of Stamford at 128 278 making it the third largest city in Connecticut. The soccer team, the New England Force is based in the city. Stamford is covered by the zip codes of 06901 to 06907 and area codes of 203 and 475.
{openx:262}
 Podiatry Clinics in Stamford: Stamford Podiatry Group Podiatrists in Stamford: Rui DeMelo, DPM
{openx:503}
 Related Topics: Connecticut Board of Examiners in Podiatry | Connecticut Podiatric Medical Association | Podiatric Practice in Connecticut  Other Locations in Connecticut: [table id=95 /] Page last updated: [last-modified]
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Workshops and training, Pacific news, world news and detailed analysis. The E51HMK - Rarotonga Island - Cook Islands Hans, DK2HMK will be operating as E51HMK of Rarotonga Island, Rarotonga Island, Rarotonga Island, Rarotonga Island, Rarotonga Island, Rarotonga Island, DK2HMK - 013, Cook Islands in March 2019. Advertisements for QSL: Hans-Martin Kurka, Telemannstr. The DXCC Country - South Cook Islands E5. About Rarotonga Island, Cook Islands.
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Cooke Islands Tourism is proud to announce two full-day photo sessions next weekend. South-pacific tourism organisation took part in the fourth meeting of Pacific culture ministers in Nadi and was presented by SPTO CEO Chris Cocker, who emphasised the importance of "culturalisation of trade" over "commercialisation of culture".
Professor Simon Milne, Director of Research and Development at the New Zealand Institute of Research on Forestry, announces a poll to take into consideration the Community's commitment to this area. Cook Islands Tourisme Corporation recently revised its data protection guidelines following the entry into force of Europe's new GDPR on 25 May.


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Q: ActionScript Defining a Static Constant Array is it not possible to define a static const array?  i would like to have an optional parameter to a function that is an array of colors,
private static const DEFAULT_COLORS:Array = new Array(0x000000, 0xFFFFFF);

public function myConstructor(colorsArray:Array = DEFAULT_COLORS)
{
}

i know i can use ...args but i actually wanting to supply the constructor with 2 separate arrays as option arguments.

A: Not possible, but you could this to simulate this behaviour:
private static const DEFAULT_COLORS:Array = new Array(0x000000, 0xFFFFFF);

public function myConstructor(colorsArray:Array = null)
{
    colorsArray = colorsArray ? colorsArray : DEFAULT_COLORS;
}

This will not work if your function is coded in a way such that null could be a valid value (to signal some condition, for instance), but probably that's not the case here.
Edit
If you plan to write to colorsArray in myConstructor, it would be wise to make a copy of DEFAULT_COLORS here:
colorsArray = colorsArray ? colorsArray : DEFAULT_COLORS.slice();

The reference to the DEFAULT_COLORS Array is constant, but its contents are not, so you could accidentally change your default values.

redpajama_set_name: RedPajamaStackExchange


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You are here: Home / Point of View / David / Green New Deal: An Economist's Perspective by David Montgomery
Green New Deal: An Economist's Perspective by David Montgomery
February 18, 2019 by David Montgomery
One of the newest and one of the oldest radicals in the U.S. Congress, Alexandra Octavio-Cortez and Ed Markey, unveiled a so-called "Green New Deal (GND)" in resolutions they filed in the House of Representatives and the Senate. The rhetoric and expansiveness of the revolution they propose makes their proposal more of a manifesto that a resolution. The areas of public policy that they address include climate change, workplace regulation, universal healthcare, and guaranteed income. More troubling, the manifesto also envisions radical changes in governance, elevating the politics of identity and victimization to the guiding principle of American government.
Since I am an economist and have tried to quantify the impacts of most major energy and environmental policies over the past 40 years, friends have asked how I would go about trying to assess the potential costs and economic impacts of the GND, in particular its determination to eliminate greenhouse gas emissions within 10 years.
Despite the ability of creative analysts to put a number on almost anything, I think that it is impossible to make a reasonable estimate of the cost of the Green New Deal in its envisioned time frame of 10 years using any kind of existing economic model. There are three reasons why this is so:
Having excluded nuclear power, it is impossible to achieve zero greenhouse gas emissions in 10 years without drastic reductions in the availability and reliability of energy
The commitment of the GND to government planning and regulation guarantees that existing economic models will grossly underestimate the cost of achieving its goals
The vision of using climate and other policies to achieve radical redistribution of income and political power will cause changes far outside the data and experience on which models are based.
Economic models are systems of equations and constraints. If one of them is used to estimate the cost of an internally contradictory program, it will simply report that the equations cannot be solved.
What GND calls renewable energy (which excludes nuclear and large scale hydro) now comprises under 10% of U.S. energy supply. Replacing 90% of electric generating capacity, gasoline and diesel fuel, and all natural gas with wind and solar, which are all that is left, is literally impossible. There is no way to store enough energy to maintain supply when the wind is not blowing and the sun is not shining, and diverting enough land to produce biofuels would drastically reduce food supply.
Even if it were possible, diverting enough resources to replacing the existing energy capital stock with renewable assets would reduce our ability to produce consumption goods. This is exactly what happened in the investment-driven 5-year plans of Chairman Mao and Stalin, starving their people along the way. Thus achieving, rather than just imagining, zero emissions would require a combination of starvation, blackouts, and rationing.
The costs of starvation, blackouts and rationing are literally impossible for economic models to capture. Some models, which impose realistic constraints on how rapidly new technologies can be introduced, would simply report that there is no solution to their equations. Others, that allow for extreme changes in consumption of energy and other goods, would give misleadingly optimistic answers about how consumers will substitute purchases of clothing and bicycles for energy. Rationing would be indistinguishable from an extremely high carbon tax, and mortality from lack of energy or food would be ignored except for the effect of a smaller labor force on GDP.
The commitment to central planning and government regulation that pervades the GND would make matters even worse. Case studies that compare specific regulatory approaches to market incentives like carbon taxes, studies have found that assuming that optimal market-based policies are used leads to gross underestimates of costs. For example, studies published in leading journals find that fuel economy standards cost 6 to 10 times more than a carbon tax designed to achieve the same reductions in CO2 emissions.
Since economic models are basically computer programs, they require a very precise description of the policies being modeled. Just like typing an email address, a small error in that specification can be fatal. The GND is vague about specific policies, and achieving its climate goals alone would require a regulatory net covering every decision about energy use and supply. We have collected mountains of data on energy since the 1970s, but still fall far short of the ability to calculate the total cost of retrofits to improve energy efficiency in every building in the country or modifications of all manufacturing processes to reduce emissions.
In the absence of specific details of the policies to be implemented and extensive data on affected economic sectors, models default to assuming that government is omniscient and adopts policies that achieve the same result as a perfect market. That leads inevitably to gross underestimation of the cost of universal government planning envisioned by the GND.
And energy policy is the subject on which we probably have the most information. Other areas of life that the GND would affect include intrusive workplace regulations, free health care, guaranteed income regardless of effort or ability and other proposals that radically change incentives for consumption, investment and labor supply. Modeling the cost of these changes is orders of magnitude harder than energy.
The vision of governance found in the GND compounds the problem. The GND resolutions introduced in Congress establish that the primary goal of GND is income redistribution and transfer of power to what it labels "frontline and vulnerable communities.'' The beneficiaries of this enshrinement of the politics of identity and victimization as a new form of governance are to include "indigenous communities, communities of color, migrant communities, deindustrialized communities, depopulated rural communities, the poor, low-income workers, women, the elderly, the unhoused, people with disabilities, and youth." In other words, if you are a healthy white male between 18 and 65 earning a decent living, do not apply.
Not only are policies to be designed to redistribute income toward these groups: they are to be designed by "democratic and participatory processes that are inclusive of and led by frontline and vulnerable communities and workers to plan, implement, and administer the Green New Deal mobilization." Sounds like the Great Cultural Revolution to me.
What this implies is not just that the GND would implement regulatory approaches with costs far higher than economic models can capture. It implies that climate, health care, labor and other regulations will be designed not just to correct specific concerns, but to achieve income redistribution and empowerment of favored constituencies.
The empirical evidence that the result cannot be modeled adequately is overwhelming. Environmental justice movements have multiplied the cost of achieving California's climate goals, by demanding inefficient choices and compensation payments in every new initiative. Developing countries demands for compensation and environmentalists objections to cost-effective ways of reducing greenhouse gas emissions have hamstrung global climate negotiations.
Economic models are neither designed for nor capable of being modified to capture the effects of changes in underlying political institutions and property rights. Historical examples can give some idea of the magnitude of harm that might be brought about: Venezuela under Chavez, Argentina under Peron, or Zimbabwe under Mugabe come to mind. Only in retrospect has it been possible to calculate the cost of socialism to the people of those countries.
One particular form of redistribution that would be likely under any policies designed to drive greenhouse gas emissions to zero over a single decade is the bankruptcy of most businesses that now own the capital equipment used to generate and distribute electricity, produce and refine petroleum, or deliver natural gas.
Getting to zero emissions in just 10 years would require shutting down all fossil-fueled power plants, oil refineries, and oil and gas production, and emptying natural gas pipelines and distribution systems. These assets would become valueless, bankruptcies would spread the loss to lenders as well as shareholders, and the financial system would suffer a major shock.
Those bankruptcies would certainly achieve some of the leveling goals of the GND, by destroying the savings and assets of every lender and equity investor in non-renewable energy. Based on the ratio of energy to total domestic investment, that would be destruction of at least 6% of the wealth of the country. The shock would likely be comparable to the recent financial crisis, as financial institutions revised their balance sheets and restricted credit, individual investors retrenched due to their reduced assets, and courts were swamped with bankruptcy filings.
Someone once said that some arguments are best refuted by a good laugh. That was my first reaction on reading descriptions of the GND. Any effort to quantify its costs would have to invent concrete programs to achieve the largely ideological goals of the GND. The harm likely to be done by the GND would greatly exceed any estimates that might be made of the cost of sensible programs. Making those estimates would only give credibility to a program that is at best a flight of fancy and more likely subversive of every institution that has supported the unprecedented prosperity of the United States.
David Montgomery is retired from a career of teaching, government service and consulting, during which he became internationally recognized as an expert on energy, environmental and climate policy. He has a PhD in economics from Harvard University and also studied economics at Cambridge University and theology at the Catholic University of America, David and his wife Esther live in St Michaels, and he now spends his time in front of the computer writing about economic, political and religious topics and the rest of the day outdoors engaged in politically incorrect activities.
Filed Under: David, Top Story
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Forest Hansen says
David Montgomery quite rightly describes implications of the Green New Deal that concerned citizens should be wary of. But while the GND is vulnerable to many of his assessments, he fails to recognize that many of the issues addressed by the GND–global warming, huge–and recent–disparities of wealth, growing costs of health care, businesses not caring for the welfare of their employees–have resulted from the very laissez-faire economic policies that he espouses. It would be interesting to read something positive from him concerning what he thinks could be preferred ways of dealing with these problems (if he even recognizes them as problems).
jan bohn says
A well written summary of a lunatic policy. Thank you for your view. Please continue to explain in your clear, concise words, why this will never work! And continue to enjoy your writing (of which I hope to read more) and time outdoors engaged in politically incorrect activities
Alan Boisvert says
There are NO issues to be argued with the Green New Deal. We simply have NO choice. Any more debate is useless BS.
Skinner says
Accept for the moment the conclusions of the author. Next, consider the conclusions of most scientists with respect to the increasing speed of global climate change and the impact of that change. Rule out anything that government might do to mitigate the magnitude of the change. Accept "that some arguments are best refuted by a good laugh." What exactly is left? More specifically, is there anything to be done to alter the course of global climate change? If the New Green Deal is so inept an idea, what – if anything – is to be done? Ought we resign ourselves to the status quo, accept that the course of events is immutable, or wait for some invisible hand of market forces to address the environment's degradation and its consequences?
The Clean Air Act and the Environmental Protection Agency came into being in 1970 and the howls of outrage about government regulation reverberated. Between 1980 and 2015, total emissions of the major pollutants included in the Act dropped by over 60 per cent and Gross Domestic Product increased.
One need not be hallucinatory, a socialist, or even an extremist to think that global climate change is immune to efforts to slow or contain its worst effects. Dismissing those ideas without suggesting alternatives to those one finds to be silly changes nothing.


PGBackups:transfer is released for database-to-database transfers.
PGBackups Transfer allows data to be migrated directly from one Heroku Postgres database to another. It can be used to upgrade databases.
Documentation on upgrading with pgbackups:transfer is available here.


Building custodians, or janitors, wash and wax floors, vacuum carpets, and clean bathrooms. They make minor repairs, such as replacing lightbulbs and fixing leaky faucets; kill insects and rodents; and collect and discard trash. Some custodians clear snow from sidewalks and mow lawns. A few collect rent and enforce building management rules. Generally, their work does not require special skills.
Many custodians work during the day, when buildings are occupied, making repairs that cannot wait, such as unclogging drains in public bathrooms. Others work only at night so they do not disturb a building's occupants. Many work for janitorial service firms and clean a number of different buildings.
Custodians' tools include floor-waxing machines, carpet sweepers, pliers, and screwdrivers. They often use chemicals to wash floors and clean carpets and bathrooms.
While there are no educational requirements for the job, high school shop courses that teach how to make simple repairs are useful. Custodians must be able to do simple arithmetic. Many employers require good character references.
Building custodians generally learn under the supervision of an experienced worker. They start by cleaning and, after gaining experience, take on repairs and more complex duties.
Job seekers can apply directly to schools, manufacturing plants, and companies that manage apartment and office buildings. Janitorial service firms are usually listed in the Yellow Pages. State employment offices, federal civil service offices, newspaper classified ads, and job banks on the Internet are other sources of job information.
Advancement for custodians often means moving to a larger building or company that offers a higher rate of pay. In large buildings that employ several custodians they can advance to the position of supervisor. Those with administrative ability sometimes start their own cleaning and maintenance services.
The employment outlook for building custodians is good through 2014. Most of the job growth is expected to be in janitorial service firms. New buildings are being constructed every day, and more custodians will be needed to maintain them. However, improvements in cleaning equipment and chemical compounds can make cleaning easier and faster, reducing the total number of workers required.
Building custodians generally work between forty and forty-eight hours a week, mostly indoors, although snow removal and grounds maintenance require outdoor work. Janitors may be scheduled for day or night shifts, depending on the individual job.
Most building custodians have a variety of duties with relatively little pressure. They may have to move furniture and other heavy objects and work with dirty, greasy machinery. They may get minor cuts, bruises, and burns from handling chemicals.
Custodians must be able to get along well with others, be courteous to other employees and occupants of the building, and be honest and trustworthy.
In 2004 the median salary for building custodians was $23,414 per year. For a senior custodian, or building custodian supervisor, the median salary was $26,918 per year. Benefits usually included paid sick leave and vacations, life and health insurance, and pension plans. Custodians who work for apartment buildings are often provided housing at no charge. Many custodians are members of labor unions.


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Is it wrong to write an article whose sole purpose is giving users new ideas how to cheat? I'm askin' here. [[Special:Contributions/65.185.185.208|65.185.185.208]] 04:22, 5 February 2009 (UTC) : I'm of the opinion that "information wants to be free". The information already exists, it's no longer possible to force it into non-existence, so there's no point in hiding it. : It's true that cheating can ruin a game (and this is an outstanding and unique game, so people shouldn't ruin it), so I ''do'' agree that individuals need to think carefully about how much and what kind of cheating they allow themselves to do. It's true that the easiest way to achieve this is "abstinence". But it's also true that (with care) it's possible to find a happy midpoint, where you cheat enough to let you progress past "permanently stuck points" so you can experience the entire game (that you otherwise wouldn't be able to), but you don't cheat enough to ruin major game mechanics. --[[Special:Contributions/Interiot|Interiot]] 15:31, 5 February 2009 (UTC) I'm think I've had the Snake Pit appear occasionally on level 1 in 0.99.5: can someone check the source code or do some more testing? It also contradicts the "dark level" scumming section, since that's a level feeling as well. - [[User:E-mouse|E-mouse]] 15:49, 5 February 2009 (UTC) : You're right. I've run across snake pits a few times on Level 1 as well. Edited accordingly. [[User:MagFlare|MagFlare]] 00:46, 8 February 2009 (UTC)
Return to Talk:Scumming.
Retrieved from "https://spelunky.fandom.com/wiki/Talk:Scumming"


1. Cannot have Out of School Suspension (OSS) during the school year.
2. Cannot have more than 2 In-School Suspension (ISS) or In-Team Suspension (ITS) during the school year.
3. Cannot have more than 4 after-school detentions during the school year.
4. Cannot have more than 10 absences (except death in the family or doctor's notes).
5. Cannot have missing books or fines (library books or curriculum books).


Cardiac Rick in the Young (CRY) holds ECG screening clinics for those aged 14 to 35 at a number of established locations around the UK including Belfast, Cardiff and London. The CRY mobile screening unit facilitates various screening events at other locations in the UK - often organised by CRY supporters.
Clinics will be held at Cornwall College Camborne and places must be booked in advance.
Please click here to book your place!


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Adaptation of Allan Bennett's stage play. Bounced between their maverick English teacher, a grossly-outnumbered history teacher and a headmaster obsessed with results, a group of students attempt to sift through it all to pass the daunting Oxbridge university admissions process. Their journey becomes as much about how education works as it is where education leads.


Get help with energy bills and housing costs.
You may be eligible if you get Housing Benefit but still can't afford your housing costs.
You could get Housing Benefit to help pay your rent if you're on a low income.
Information on how to apply for housing benefit if you're renting privately.