More Like this

1. Benchmarking of hydrodynamic plasma waveguides for multi-GeV laser-driven electron acceleration

   https://doi.org/10.1103/PhysRevAccelBeams.27.081302  

   Miao, B; Rockafellow, E; Shrock, J E; Hancock, S W; Gordon, D; Milchberg, H M (August 2024, Physical Review Accelerators and Beams)

   Hydrodynamic plasma waveguides initiated by optical field ionization have recently become a key component of multi-GeV laser wakefield accelerators. Here, we present the most complete and accurate experimental and simulation-based characterization to date, applicable to current multi-GeV experiments and future 100 GeV-scale laser plasma accelerators. Crucial to the simulations is the correct modeling of intense Bessel beam interaction with meter-scale gas targets, the results of which are used as initial conditions for hydrodynamic simulations. The simulations are in good agreement with our experiments measuring evolving plasma and neutral hydrogen density profiles using two-color short pulse interferometry, enabling realistic determination of the guided mode structure for application to laser-driven plasma accelerator design. Published by the American Physical Society2024 

   more » « less
2. Photon-Counting Interferometry to Detect Geontropic Space-Time Fluctuations with GQuEST

   https://doi.org/10.1103/PhysRevX.15.011034  

   Vermeulen, Sander M; Cullen, Torrey; Grass, Daniel; MacMillan, Ian_A O; Ramirez, Alexander J; Wack, Jeffrey; Korzh, Boris; Lee, Vincent_S H; Zurek, Kathryn M; Stoughton, Chris; et al (February 2025, Physical Review X)

   The gravity from the quantum entanglement of space-time (GQuEST) experiment uses tabletop-scale Michelson laser interferometers to probe for fluctuations in space-time. We present a practicable interferometer design featuring a novel photon-counting readout method that provides unprecedented sensitivity, as it is not subject to the interferometric standard quantum limit. We evaluate the potential of this design to measure space-time fluctuations motivated by recent “geontropic” quantum gravity models. The accelerated accrual of Fisher information offered by the photon-counting readout enables GQuEST to detect the predicted quantum gravity phenomena within measurement times at least 100 times shorter than equivalent conventional interferometers. The GQuEST design, thus, enables a fast and sensitive search for signatures of quantum gravity in a laboratory-scale experiment. Published by the American Physical Society2025 

   more » « less
3. Source anisotropies and pulsar timing arrays

   https://doi.org/10.1103/PhysRevD.110.123507  

   Allen, Bruce; Agarwal, Deepali; Romano, Joseph D; Valtolina, Serena (December 2024, Physical Review D)

   Pulsar timing arrays (PTAs) hunt for gravitational waves (GWs) by searching for the correlations that GWs induce in the time-of-arrival residuals from different pulsars. If the GW sources are of astrophysical origin, then they are located at discrete points on the sky. However, PTA data are often modeled, and subsequently analyzed, via a “standard Gaussian ensemble.” That ensemble is obtained in the limit of an infinite density of vanishingly weak, Poisson-distributed sources. In this paper, we move away from that ensemble, to study the effects of two types of “source anisotropy.” The first (a), which is often called “shot noise,” arises because there are $N$discrete GW sources at specific sky locations. The second (b) arises because the GW source positions are not a Poisson process, for example, because galaxy locations are clustered. Here, we quantify the impact of (a) and (b) on the mean and variance of the pulsar-averaged Hellings and Downs correlation. For conventional PTA sources, we show that the effects of shot noise (a) are much larger than the effects of clustering (b). Published by the American Physical Society2024 

   more » « less
4. Universal density shift coefficients for the thermal conductivity and shear viscosity of a unitary Fermi gas

   https://doi.org/10.1103/PhysRevResearch.6.L042021  

   Li, Xiang; Huang, J; Thomas, J E (October 2024, Physical Review Research)

   We measure universal temperature-independent density shifts for the thermal conductivity ${\kappa }_T$and shear viscosity $\eta$, relative to the high temperature limits, for a normal phase unitary Fermi gas confined in a box potential. We show that a time-dependent kinetic theory model enables extraction of the hydrodynamic transport times ${\tau }_{\eta }$and ${\tau }_{\kappa }$from the time-dependent free decay of a spatially periodic density perturbation, yielding the static transport properties and density shifts, corrected for finite relaxation times. Published by the American Physical Society2024 

   more » « less
5. Circularly polarized photon emission from magnetized chiral plasmas

   https://doi.org/10.1103/PhysRevD.110.116005  

   Wang, Xinyang; Shovkovy, Igor A (December 2024, Physical Review D)

   We investigate the emission of circularly polarized photons from a magnetized quark-gluon plasma with nonzero quark-number and chiral charge chemical potentials. These chemical potentials qualitatively influence the differential emission rates of circularly polarized photons. A nonzero net electric charge density, induced by quark-number chemical potentials, enhances the overall emission of one circular polarization over the other, while a nonzero chiral charge density introduces a spatial asymmetry in the emission with respect to reflection in the transverse plane. The signs of the electrical and chiral charge densities determine which circular polarization dominates overall and whether the emission preferentially aligns with or opposes the magnetic field. Based on these findings, we propose that polarized photon emission is a promising observable for characterizing the quark-gluon plasma produced in heavy-ion collisions. Published by the American Physical Society2024 

   more » « less