Abstract
We propose a practical scheme to use photons from causally disconnected cosmic sources to set the detectors in an experimental test of Bell’s inequality. In current experiments, with settings determined by quantum random number generators, only a small amount of correlation between detector settings and local hidden variables, established less than a millisecond before each experiment, would suffice to mimic the predictions of quantum mechanics. By setting the detectors using pairs of quasars or patches of the cosmic microwave background, observed violations of Bell’s inequality would require any such coordination to have existed for billions of years—an improvement of 20 orders of magnitude.
Abstract
We investigate the dewetting of a disordered melt of diblock copolymer from an ordered residual wetting layer. In contrast to simple liquids where the wetting layer has a fixed thickness and the droplets exhibit a single unique contact angle with the substrate, we find that structured liquids of diblock copolymer exhibit a discrete series of wetting layer thicknesses each producing a different contact angle. These quantized contact angles arise because the substrate and air surfaces each induce a gradient of lamellar order in the wetting layer. The interaction between the two surface profiles creates an effective interface potential that oscillates with film thickness, thus, producing a sequence of local minimums. The wetting layer thicknesses and corresponding contact angles are a direct measure of the positions and depths of these minimums Self-consistent field theory is shown to provide qualitative agreement with the experiment.
Abstract
We show that the existence of new, light gauge interactions coupled to Standard Model (SM) neutrinos gives rise to an abundance of sterile neutrinos through the sterile neutrinos’ mixing with the SM. Specifically, in the mass range of MeV–GeV and coupling of \( g' \sim 10^{-6} \)–\( 10^{-3} \), the decay of this new vector boson in the early Universe produces a sufficient quantity of sterile neutrinos to account for the observed dark matter abundance. Interestingly, this can be achieved within a natural extension of the SM gauge group, such as a gauged \( L_{\mu} \) − \( L_{\tau} \) number, without any tree-level coupling between the new vector boson and the sterile neutrino states. Such new leptonic interactions might also be at the origin of the well-known discrepancy associated with the anomalous magnetic moment of the muon.
Abstract
It has recently been shown that dark-matter annihilation to bottom quarks provides a good fit to the Galactic Center gamma-ray excess identified in the Fermi-LAT data. In the favored dark-matter mass range \( m \sim \) 30–40 GeV, achieving the best-fit annihilation rate \( \sigma v \sim 5 \times 10^{-26} \, \mathrm{cm^3 s^{-1}} \) with perturbative couplings requires a sub-TeV mediator particle that interacts with both dark matter and bottom quarks. In this paper, we consider the minimal viable scenarios in which a Standard Model singlet mediates s-channel interactions only between dark matter and bottom quarks, focusing on axial-vector, vector, and pseudoscalar couplings. Using simulations that include on-shell mediator production, we show that existing sbottom searches currently offer the strongest sensitivity over a large region of the favored parameter space explaining the gamma-ray excess, particularly for axial-vector interactions. The 13 TeV LHC will be even more sensitive; however, it may not be sufficient to fully cover the favored parameter space, and the pseudoscalar scenario will remain unconstrained by these searches. We also find that direct- detection constraints, induced through loops of bottom quarks, complement collider bounds to disfavor the vector-current interaction when the mediator is heavier than twice the dark-matter mass. We also present some simple models that generate pseudoscalar-mediated annihilation predominantly to bottom quarks.
Abstract
Baryogenesis through neutrino oscillations is an elegant mechanism that has found several realizations in the literature corresponding to different parts of the model parameter space. Its appeal stems from its minimality and dependence only on physics below the weak scale. In this paper we show that by focusing on the physical time scales of leptogenesis instead of the model parameters, a more comprehensive picture emerges. The different regimes previously identified can be understood as different relative orderings of these time scales. This approach also shows that all regimes require a coincidence of time scales and this in turn translates to a certain tuning of the parameters, whether in mass terms or Yukawa couplings. Indeed, we show that the amount of tuning involved in the minimal model is never less than one part in 105 according to a metric constructed from a combination of the sterile neutrino mass degeneracy and the Barbieri-Giudice tuning of the Yukawa coupling. Finally, we explore an extended model, where the tuning can be removed in exchange for the introduction of a new degree of freedom in the form of a leptophilic Higgs with a vacuum expectation value of the order of GeV.
Abstract
We present a simple cryostat purpose built for use with surface-electrode ion traps, designed around an affordable, large cooling power commercial pulse tube refrigerator. A modular vacuum enclosure with a single vacuum space facilitates interior access and enables rapid turnaround and flexibility for future modifications. Long rectangular windows provide nearly 360 degrees of optical access in the plane of the ion trap, while a circular bottom window near the trap enables NA 0.4 light collection without the need for in-vacuum optics. We evaluate the system's mechanical and thermal characteristics and we quantify ion trapping performance by trapping 40Ca+, finding small stray electric fields, long ion lifetimes, and low ion heating rates.
