Computers with closed timelike curves can solve hard problems
<|reference_start|>Computers with closed timelike curves can solve hard problems: A computer which has access to a closed timelike curve, and can thereby send the results of calculations into its own past, can exploit this to solve difficult computational problems efficiently. I give a specific demonstration of this for the problem of factoring large numbers, and argue that a similar approach can solve NP-complete and PSPACE-complete problems. I discuss the potential impact of quantum effects on this result.<|reference_end|>
@article{brun2002computers,
    title={Computers with closed timelike curves can solve hard problems},
    author={Todd A. Brun (Institute for Advanced Study)},
    journal={Found.Phys.Lett. 16 (2003) 245-253},
    year={2002},
    doi={10.1023/A:1025967225931},
    archivePrefix={arXiv},
    eprint={gr-qc/0209061},
    primaryClass={gr-qc cs.CC quant-ph}
}