Jackiw-Teitelboim Gravity from the Karch-Randall Braneworld.

In this Letter, we show that Jackiw-Teitelboim gravity can be naturally realized in the Karch-Randall braneworld. Notably the role of the dilaton in Jackiw-Teitelboim gravity is played by the radion in a suitably orbifolded version of the setup. In the classical entanglement entropy calculation, there is an apparent degeneracy of Ryu-Takayanagi surfaces. We demonstrate how quantum fluctuations of the radion/dilaton resolve this would-be classical puzzle regarding entanglement wedge reconstruction.

Reaching out.

In the midst of the COVID-19 pandemic, science is crucial to inform public policy. At the same time, mistrust of scientists and misinformation about scientific facts are rampant. Six scientists, actively involved in outreach, reflect on how to build a better understanding and trust of science.

Dark matter as a trigger for periodic comet impacts.

Although statistical evidence is not overwhelming, possible support for an approximately 35×106 yr periodicity in the crater record on Earth could indicate a nonrandom underlying enhancement of meteorite impacts at regular intervals. A proposed explanation in terms of tidal effects on Oort cloud comet perturbations as the Solar System passes through the galactic midplane is hampered by lack of an underlying cause for sufficiently enhanced gravitational effects over a sufficiently short time interval and by the time frame between such possible enhancements. We show that a smooth dark disk in the galactic midplane would address both these issues and create a periodic enhancement of the sort that has potentially been observed. Such a disk is motivated by a novel dark matter component with dissipative cooling that we considered in earlier work. We show how to evaluate the statistical evidence for periodicity by input of appropriate measured priors from the galactic model, justifying or ruling out periodic cratering with more confidence than by evaluating the data without an underlying model. We find that, marginalizing over astrophysical uncertainties, the likelihood ratio for such a model relative to one with a constant cratering rate is 3.0, which moderately favors the dark disk model. Our analysis furthermore yields a posterior distribution that, based on current crater data, singles out a dark matter disk surface density of approximately 10M⊙/pc2. The geological record thereby motivates a particular model of dark matter that will be probed in the near future.

Dark-disk universe.

We point out that current constraints on dark matter imply only that the majority of dark matter is cold and collisionless. A subdominant fraction of dark matter could have much stronger interactions. In particular, it could interact in a manner that dissipates energy, thereby cooling into a rotationally supported disk, much as baryons do. We call this proposed new dark matter component double-disk dark matter (DDDM). We argue that DDDM could constitute a fraction of all matter roughly as large as the fraction in baryons, and that it could be detected through its gravitational effects on the motion of stars in galaxies, for example. Furthermore, if DDDM can annihilate to gamma rays, it would give rise to an indirect detection signal distributed across the sky that differs dramatically from that predicted for ordinary dark matter. DDDM and more general partially interacting dark matter scenarios provide a large unexplored space of testable new physics ideas.

Legal considerations surrounding mandatory influenza vaccination for healthcare workers in the United States.

Recent years have brought increased focus on the desirability of vaccinating more healthcare workers against influenza. The concern that novel 2009 H1N1 influenza A would spark a particularly severe influenza season in 2009-2010 spurred several institutions and one state to institute mandatory vaccination policies for healthcare workers, and several new mandates have been introduced since then. Some healthcare workers, however, have voiced objections in the media and in legal proceedings. This paper reviews the characteristics of influenza and how it is transmitted in the healthcare setting; surveys possible constitutional, administrative, and common law arguments against mandates; assesses the viability of those arguments; and identifies potential new legal strategies to support influenza vaccine mandates. It is intended to assist those involved in the regulation and administration of public and private healthcare institutions who may be considering approaches to mandates but have concerns about legal challenges.

Dijet searches for supersymmetry at the large hadron collider.

We present several strategies for searching for supersymmetry in dijet channels, using the two leading jets' momenta alone rather than the full missing transverse energy. Preliminary investigations suggest that signal-to-background ratios of at least 4-5 should be achievable at the LHC, with discovery possible for squarks as heavy as approximately 1.7 TeV.

Flavor anarchy in a Randall-Sundrum model with 5D minimal flavor violation and a low Kaluza-Klein scale.

A variant of a warped extra dimension model is presented. It is based on 5D minimal flavor violation, in which the only sources of flavor breaking are two 5D anarchic Yukawa matrices. These matrices also control the bulk masses, which are responsible for the resulting flavor hierarchy. The theory flows to a next to minimal flavor violation model where flavor violation is dominantly coming from the 3rd generation. Flavor violation is also suppressed by a parameter that dials the violation in the up or down sector. There is therefore a sharp limit in which there is no flavor violation in the down-type quark sector which, remarkably, is consistent with the observed flavor parameters. This is used to eliminate the current Randall-Sundrum flavor and CP problem. Our construction suggests that strong dynamic-based, flavor models may be built based on the same concepts.

Relaxing to three dimensions.

We propose a new selection principle for distinguishing among possible vacua that we call the "relaxation principle." The idea is that the Universe will naturally select among possible vacua through its cosmological evolution, and the configuration with the biggest filling fraction is the likeliest. We apply this idea to the question of the number of dimensions of space. We show that under conventional (but higher-dimensional) Friedmann-Robertson-Walker evolution, a universe filled with equal numbers of branes and antibranes will naturally come to be dominated by 3-branes and 7-branes. We show why this might explain the number of dimensions that are experienced in our visible Universe.

Dynamical approach to the cosmological constant.

We consider a dynamical approach to the cosmological constant. There is a scalar field with a potential whose minimum occurs at a generic, but negative, value for the vacuum energy, and it has a nonstandard kinetic term whose coefficient diverges at zero curvature as well as the standard kinetic term. Because of the divergent coefficient of the kinetic term, the lowest energy state is never achieved. Instead, the cosmological constant automatically stalls at or near zero. The merit of this model is that it is stable under radiative corrections and leads to stable dynamics, despite the singular kinetic term. The model is not complete, however, in that some reheating is required. Nonetheless, our approach can at the very least reduce fine-tuning by 60 orders of magnitude or provide a new mechanism for sampling possible cosmological constants and implementing the anthropic principle.

Extranatural inflation.

We present a new model of inflation in which the inflaton is the extra component of a gauge field in a 5D theory compactified on a circle. The chief merit of this model is that the potential comes only from nonlocal effects so that its flatness is not spoiled by higher-dimensional operators or quantum gravity corrections. The model predicts a red spectrum (n approximately 0.96) and a significant production of gravitational waves (r approximately 0.11). We also comment on the relevance of this idea to quintessence.

Extra dimensions and warped geometries.

The field of extra dimensions, as well as the hypothesized sizes of extra dimensions, have grown by leaps and bounds over the past few years. I summarize the new results and the reasons for the recent activity in this field. These include the observations that extra dimensions can be macroscopic or even infinite in size. Another new development is the application of extra dimensions to the determination of particle physics parameters and properties.

Unification and hierarchy from 5D anti-de Sitter space.

We show that perturbative high scale unification and a solution to the hierarchy problem are possible with extra dimensions in the context of the warped geometry of 5D anti-de Sitter space ( AdS(5)). This is possible because the couplings for bulk gauge bosons run logarithmically below the AdS(5) curvature scale. The calculation is done in five dimensions, rather than in the effective theory, which is strongly coupled above the TeV scale.

Solid-Phase Combinatorial Synthesis of Polyisoxazolines: A Two-Reaction Iterative Protocol.

Starting from a polymer-bound olefin, iterative application of nitrile oxide 1,3-dipolar cycloaddition and selenide oxidation/elimination steps were employed to deliver a polymer-bound triisoxazoline that can be liberated from the resin by transesterification. When four nitroseleno ethers (2-5) and four capping nitroalkanes (6-9) were employed, a triisoxazoline library (V) of 64 positional isomers was obtained by three iterative applications of these two reactions. The tactical flexibility of this strategy for preparing small polyfunctional oligomers is particularly attractive in that each subunit addition proceeds via a C-C bond-forming step.