The Effects of Gravitational Slip on the Higher-Order Moments of the Matter Distribution

Cosmological departures from general relativity offer a possible explanation for the cosmic acceleration. To linear order, these departures (quantified by the model-independent parameter $\varpi$, referred to as a `gravitational slip') amplify or suppress the growth of structure in the universe relative to what we would expect to see from a general relativistic universe lately dominated by a cosmological constant. As structures collapse and become more dense, linear perturbation theory is an inadequate descriptor of their behavior, and one must extend calculations to non-linear order. If the effects of gravitational slip extend to these higher orders, we might expect to see a signature of $\varpi$ in the bispectrum of galaxies distributed on the sky. We solve the equations of motion for non-linear perturbations in the presence of gravitational slip and find that, while there is an effect on the bispectrum, it is too weak to be detected with present galaxy surveys. We also develop a formalism for incorporating scale dependence into our description of gravitational slip.Comment: 25 pages, 9 figure

Book Review: Encounters with Hinduism

A review of Encounters with Hinduism by Horst Georg Pöhlmann

Is HBT really puzzling?

Two-particle correlations from RHIC have provided a surprising snapshot of the final state at RHIC. In this talk I discuss the nature of the HBT puzzle and attempt to delineate several factors which might ultimately resolve the issue.Comment: Proceedings for WPCF, Kromeriz, Czech Republic, August 200

Audaciously Hopeful: How President Obama Can Help Restore the Pro-Trade Consensus

There is reason for grave concern about the direction of U.S. trade policy. The bipartisan, pro-trade consensus that served U.S. economic and diplomatic interests so well for so long collapsed during the final two years of the Bush administration. Trade skeptics have increased their ranks in the new Congress, a majority of Americans perceive trade as threatening, and grim economic news has made the political climate inhospitable to arguments in support of trade. But restoring the pro-trade consensus must be a priority of the Obama administration. If the United States indulges misplaced fears, restrains economic freedoms, and attempts to retreat from the global economy, the country will suffer slower economic growth and have greater difficulty facing future economic and foreign policy challenges. America's trade skepticism is largely the product of a top-down process. Perceptions have been shaped overwhelmingly by relentless political rhetoric that relies on three myths. Congress and the media have spoken for years about the decline of U.S. manufacturing as though it were fact, when the overwhelming evidence points to a sector that, until the onset of the current recession, was robust and setting performance records. Both lament the U.S. trade deficit without attempting to convey or even understand its causes, meaning, or implications. And both attribute these alleged failures of policy to lax enforcement of existing trade agreements. President Obama should reexamine these premises. He will find that they are long on fallacy and short on fact. Meanwhile, the president will find it necessary to rein in the congressional leadership's increasingly provocative approach to trade policy if he is to have success repairing America's foreign policy credibility. The determination of the president to arrest and reverse America's misguided and metastasizing aversion to trade could dramatically improve prospects for restoring the pro-trade consensus

BosonSampling with Lost Photons

BosonSampling is an intermediate model of quantum computation where linear-optical networks are used to solve sampling problems expected to be hard for classical computers. Since these devices are not expected to be universal for quantum computation, it remains an open question of whether any error-correction techniques can be applied to them, and thus it is important to investigate how robust the model is under natural experimental imperfections, such as losses and imperfect control of parameters. Here we investigate the complexity of BosonSampling under photon losses---more specifically, the case where an unknown subset of the photons are randomly lost at the sources. We show that, if $k$ out of $n$ photons are lost, then we cannot sample classically from a distribution that is $1/n^{\Theta(k)}$-close (in total variation distance) to the ideal distribution, unless a $\text{BPP}^{\text{NP}}$ machine can estimate the permanents of Gaussian matrices in $n^{O(k)}$ time. In particular, if $k$ is constant, this implies that simulating lossy BosonSampling is hard for a classical computer, under exactly the same complexity assumption used for the original lossless case.Comment: 12 pages. v2: extended concluding sectio

Probabilistic dose distribution from interfractional motion in carbon ion radiation therapy for prostate cancer shows rectum sparing with moderate target coverage degradation

学位記番号：医博甲171