We present a microscopic dynamical model to study the formation, dissociation, and recombination processes of charmonium states in a heat bath at constant temperature and volume. Within this classical approach, heavy quarks are described as Brownian particles in a background medium of light constituents and can therefore be modeled by a Fokker-Planck equation with constant transport coefficients, which is then implemented through relativistic Langevin simulations. The heavy quarks interact classically via a Coulomb-like screened potential to form a bound state if the relative energy of the pair becomes negative. Dissociation of bound states is possible as a result of screening effects on the potential as well as through scatterings with plasma particles. We demonstrate the full equilibration of the system and show that the resulting equilibrium charmonium yields are in accordance with the Statistical Hadronization Model.

We propose a first-order theory of relativistic dissipative fluids in the trace-fixed particle frame, which is similar to Eckart’s frame except that the temperature is determined by fixing the trace of the stress-energy tensor. Our theory is hyperbolic and causal provided a single inequality holds. For low wave numbers, the expected damped modes in the shear, acoustic, and heat diffusion channels are recovered. Stability of global equilibria with respect to all wave numbers is also analyzed. The conditions for hyperbolicity, causality, and stability are satisfied for a simple gas of hard spheres or disks.

We study homogenous and isotropic quantum cosmology using the spinfoam formalism of loop quantum gravity (LQG). We define a coupling of a scalar field to the 4-dimensional Lorentzian Engle-Pereira-Rovelli-Livine (EPRL) spinfoam model. We employ the numerical method of complex critical points to investigate the model on two different simplicial complexes: the triangulations of a single hypercube and two connected hypercubes. We find nontrivial implications for the effective cosmological dynamics. In the single-hypercube model, the numerical results suggest an effective Friedmann equation with a scalar density that contains higher-order derivatives and a scalar potential. The scalar potential plays a role similar to a positive cosmological constant and drives an accelerated expansion of the universe. The double-hypercubes model resembles a symmetric cosmic bounce, and a similar effective Friedmann equation emerges with higher-order derivative terms in the effective scalar density, whereas the scalar potential becomes negligible.

We investigate the fermionic properties of a dyonic Gubser-Rocha model in the context of gauge/gravity duality. This model incorporates both a magnetic field and momentum relaxation. We have derived this model’s scaling exponent, revealing the influence of the magnetic field and momentum relaxation on low-energy physics. As the magnetic field strength and momentum relaxation increase, the spectral function of the dual field changes significantly. Specifically, we observe variations in the scaling exponent, Fermi momentum, and dispersion relations as the magnetic field increases, highlighting the system’s transition from a Fermi liquid to a non-Fermi liquid, and eventually to an insulating state. Our analysis of the magneto-scattering rate reveals that it is nearly zero in the Fermi liquid region, increases significantly in the non-Fermi liquid region, and ultimately arrives at a maximum value in the insulating state.

We consider a string on a Jordanian deformation of the ${\mathrm{AdS}}_5\times S^5$ spacetime. This model belongs to the larger class of homogeneous Yang-Baxter deformations, which preserve classical integrability in the sense that one can construct an explicit Lax connection. To study the scattering of bosonic worldsheet excitations, we fix light-cone gauge and expand around a pointlike classical solution that reduces to the BMN vacuum in the undeformed limit. Our analysis shows that the light-cone gauge-fixed Hamiltonian, under a perturbative field expansion, includes cubic terms that give rise to nontrivial cubic processes for physical particles. We discuss this unexpected result in relation to the property of Lax integrability of the sigma-model.

The probability distribution for vacuum fluctuations of the energy flux in two dimensions is constructed, along with the joint distribution of energy flux and energy density. Our approach is based on previous work on probability distributions for the energy density in two-dimensional conformal field theory. In both cases, the relevant stress tensor component must be averaged in time, and the results are sensitive to the form of the averaging function. Here we present results for two classes of such functions, which include the Gaussian and Lorentzian functions. The distribution for the energy flux is symmetric, unlike that for the energy density. In both cases, the distribution may possess an integrable singularity. The functional form of the flux distribution function involves a modified Bessel function and is distinct from the shifted Gamma form for the energy density. By considering the joint distribution of energy flux and energy density, we show that the distribution of energy flux tends to be more centrally concentrated than that of the energy density. We also determine the distribution of energy fluxes, conditioned on the energy density being negative. Some applications of the results are also discussed.

In this paper we derive a new first-order theory of relativistic dissipative fluids by adopting the trace-fixed particle frame. Whereas in a companion Letter we show that this theory is hyperbolic, causal, and stable at global equilibrium states, here we prove that the full nonlinear system of equations can be cast into a first-order quasilinear system which is strongly hyperbolic. By rewriting the system in first-order form, auxiliary constraints are introduced. However, we show that these constraints propagate, and thus our theory leads to a well-posed Cauchy problem.

We present a canonical model of spherical gravity with covariant corrections motivated by loop quantum gravity. The effective Hamiltonian defines univocally a family of geometries that generalizes the Lemaître-Tolman-Bondi spacetimes, and they can be matched to the vacuum of the theory across a timelike hypersurface comoving with the flow of matter. Such is precisely the complete spacetime picture of a spherical star subject to its own gravitational pull. The singularity gets replaced with a spacelike boundary in the trapped region of spacetime, where the curvature remains finite, and the area of the orbits of the spherical symmetry group attains its infimum. Observers falling into the black hole are doomed to travel forever towards this boundary without ever reaching it. The theory also predicts the formation of stable black-hole remnants of Planckian mass.

The hypothesis that classical scalar fields could constitute dark matter on galactic and cosmic scales has garnered significant interest. In scenarios where supermassive black holes (SMBHs) form through the accretion of matter onto black hole seeds, a critical question arises: what role does dark matter play in this process? We conduct a numerical investigation into the nonlinear dynamical evolution of black hole shadows and gravitational lensing effects resulting from the accretion of an ultralight, real scalar field onto a nonrotating black hole. The scalar field is minimally coupled to Einstein’s gravity, and our simulations focus on wave packets, parametrized by their wave number and width, as they interact with and are accreted by a dynamic black hole. Our results demonstrate significant growth in the apparent horizon, photon ring, and Einstein ring sizes compared to those of a Schwarzschild black hole. These findings suggest that the observed photon ring and black hole shadow in Sgr A*, and M87* may be influenced by the gravitational interaction between the black hole and ultralight scalar field dark matter.

We present a joint analysis of the cosmic microwave background (CMB) lensing power spectra measured from the Data Release 6 of the Atacama Cosmology Telescope (ACT) and Planck PR4, cross-correlations between the ACT and Planck lensing reconstruction and galaxy clustering from unWISE, and the unWISE clustering auto-spectrum. We obtain 1.5% constraints on the matter density fluctuations at late times parametrized by the best constrained parameter combination $S_8^{3\mathrm{x}2\mathrm{pt}}\equiv {\sigma }_8({\mathrm{\Omega }}_m/0.3{)}^{0.4}=0.815\pm 0.012$. The commonly used $S_8\equiv {\sigma }_8({\mathrm{\Omega }}_m/0.3{)}^{0.5}$ parameter is constrained to $S_8=0.816\pm 0.015$. In combination with baryon acoustic oscillation (BAO) measurements we find ${\sigma }_8=0.815\pm 0.012$. We also present sound-horizon-independent estimates of the present day Hubble rate of $H_0={66.4}_{-3.7}^{+3.2}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$ from our large scale structure data alone and $H_0={64.3}_{-2.4}^{+2.1}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$ in combination with uncalibrated supernovae from Pantheon+. Using parametric estimates of the evolution of matter density fluctuations, we place constraints on cosmic structure in a range of high redshifts typically inaccessible with cross-correlation analyses. Combining lensing cross- and autocorrelations, we derive a 3.3% constraint on the integrated matter density fluctuations above $z=2.4$, one of the tightest constraints in this redshift range and fully consistent with a $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) model fit to the primary CMB from Planck. Finally, combining with primary CMB observations and using the extended low redshift coverage of these combined datasets we derive constraints on a variety of extensions to the $\mathrm{\Lambda }\mathrm{CDM}$ model including massive neutrinos, spatial curvature, and dark energy. We find in flat $\mathrm{\Lambda }\mathrm{CDM}\sum m_{\nu }<0.12\mathrm{eV}$ at 95% confidence using the large scale structure data, BAO measurements from Sloan Digital Sky Survey, and primary CMB observations.

We provide a perturbative effective field theory (EFT) description for anisotropic (redshift-space) correlations between the Lyman alpha forest and a generic biased tracer of matter, which could be represented by quasars, high-redshift galaxies, or dark matter halos. We compute one-loop EFT power spectrum predictions for the combined analysis of the Lyman alpha and biased tracers’ data and test them on the publicly available high-fidelity Sherwood simulations. We use massive and light dark matter halos at redshift $z=2.8$ as proxies for quasars and high-redshift galaxies, respectively. In both cases, we demonstrate that our EFT model can consistently describe the complete data vector consisting of the Lyman alpha forest auto spectrum, the halo auto spectrum, and the Lyman alpha-halo cross spectrum. We show that the addition of cross-correlations significantly sharpens constraints on EFT parameters of the Lyman alpha forest and halos. In the combined analysis, our EFT model fits the simulated cross-spectra with a percent level accuracy at $k_{\max }=1h{\mathrm{Mpc}}^{-1}$, which represents a significant improvement over previous analytical models. Thus, our work provides precision theoretical tools for full-shape analyses of Lyman alpha-quasar cross-correlations with ongoing and upcoming spectroscopic surveys.

It is well known that alternative theories to the Standard Model allow—and sometimes require—fundamental constants, such as the fine-structure constant, $\alpha$, to vary in spacetime. We demonstrate that one way to investigate these variations is through the mass-radius relation of compact astrophysical objects, which is inherently affected by $\alpha$ variations. We start by considering the model of a polytropic white dwarf, which we perturb by adding the $\alpha$ variations for a generic class of Grand Unified Theories. We then extend our analysis to neutron stars, building upon the polytropic approach to consider more realistic equations of state, discussing the impact of such variations on mass-radius measurements in neutron stars. We present some constraints on these models based on current data and also outline how future observations might distinguish between extensions of the Standard Model.

The canonical signal model in continuous gravitational wave searches is deterministic, and stable over the long integration times needed to separate a putative signal from the noise, e.g., with a matched filter. However, there exist plausible physical mechanisms that give rise to “spin-wandering,” i.e., small stochastic variations in the frequency of the gravitational wave. Stochastic variations degrade the sensitivity of matched filters which assume a deterministic frequency evolution. Suites of synthetic spin-wandering injections are performed to infer the loss in sensitivity depth ${\mathcal{D}}_{\mathrm{SW}}$ when compared to the depth for a canonical signal ${\mathcal{D}}_{\det }$. For a fiducial spin-wandering signal that wanders by $\lesssim 5\times {10}^{-6}\mathrm{Hz}$ per day, the depth ratio is ${\mathcal{D}}_{\det }/{\mathcal{D}}_{\mathrm{SW}}=4.39_{-0.27}^{+0.23}$, ${1.51}_{-0.03}^{+0.02}$, ${1.75}_{-0.04}^{+0.04}$, and ${1.07}_{-0.02}^{+0.01}$ for the coherent $\mathcal{F}$-statistic, semicoherent $\mathcal{F}$-statistic, CrossCorr, and HMM-Viterbi algorithms respectively. Increasing the coherence time of the semicoherent algorithms does not necessarily increase their sensitivity to spin-wandering signals.

Terrestrial long-baseline atom interferometer experiments are emerging as powerful tools for probing new fundamental physics, including searches for dark matter and gravitational waves. In the frequency range relevant to these signals, gravity gradient noise (GGN) poses a significant challenge. While previous studies for vertical instruments have focused on GGN induced by seismic waves, atmospheric fluctuations in pressure and temperature also lead to variations in local gravity. In this work, we advance the understanding of atmospheric GGN in vertical atom interferometers, formulating a robust characterization of its impact. We evaluate the effectiveness of underground placement of atom interferometers as a passive noise mitigation strategy. Additionally, we empirically derive global high- and low-noise models for atmospheric pressure GGN and estimate an analogous range for atmospheric temperature GGN. To highlight the variability of temperature-induced noise, we compare data from three prospective experimental sites. Our findings establish atmospheric GGN as comparable to seismic noise in its impact and underscore the importance of including these effects in site selection and active noise monitoring for future experiments.

We explore the most general phenomenology of charged lepton flavor violating (CLFV) decays of muon and tau leptons to the three body final states $(\overline{e}ee,\overline{\mu }\mu \mu ,\overline{e}\mu \mu ,\overline{\mu }\mu e,\overline{\mu }ee,\overline{e}e\mu )$. By constructing a complete basis of operators at each dimension, we derive the most general amplitudes for these decay processes. By considering constraints from unitarity and Large Electron-Positron Collider (LEP), we show that operators of mass dimension 6 and 7 are the most likely to be observed in next generation experiments. Focusing on these dimensions, we compute the results of unpolarized (spin-averaged) decays parametrized in terms of the invariant masses of the daughter particles. We also compute the differential decay rates for polarized decays, in anticipation of the experimental search Mu3e, which expects to have a muon beam with $\sim 90\%$ polarization, and the chiral Belle proposal, which aims to have a 70% polarized electron beam. To determine the extent to which the operators may be distinguished experimentally, we plot the differential distributions for each operator, showing that they leave only a few possible degenerate explanations. Through a statistical analysis, we estimate the number of events needed to break the degeneracies using the angular information. These results are adapted to treat $\ell \to {\ell }^{\prime }\nu \overline{\nu }$, where the angular distribution of the outgoing charged lepton has enhanced distinguishing power. With many Standard Model extensions predicting these CLFV decays, these results will better enable upcoming searches to identify and/or constrain physics beyond the Standard Model.

We present the first lattice gauge theory results for hybrid spin-dependent and hybrid-quarkonium mixing potentials appearing at order $(1/m_Q{)}^1$ in the Born-Oppenheimer effective field theory for hybrid mesons with gluon spin ${\kappa }^{PC}=1^{+-}$. Specifically, we compute the four unknown potentials $V_{11}^{sa}(r)$, $V_{10}^{sb}(r)$, which are relevant for the hyperfine splitting in heavy hybrid meson spectra, as well as $V_{{\mathrm{\Sigma }}_u^{-}}^{\mathrm{mix}}(r)$ and $V_{{\mathrm{\Pi }}_u}^{\mathrm{mix}}(r)$, which describe the mixing of heavy hybrid mesons with ordinary quarkonium. We relate these potentials to matrix elements, which we extract from generalized Wilson loops with a chromomagnetic field insertion along one of the temporal lines and suitable hybrid creation operators replacing the spatial lines. We use gradient flow, which facilitates the renormalization of the matrix elements and has the additional benefit of significantly reducing statistical noise. We present results for gauge group SU(3) and lattice spacing $a=0.060\mathrm{fm}$. Our results demonstrate that a future combined continuum and zero-flow time extrapolation is possible within our setup, which will be necessary to reliably predict the hyperfine splitting of heavy hybrid mesons as well as their mixing with ordinary quarkonium through coupled channel Schrödinger equations.

We extend the derivation of second-order relativistic viscous hydrodynamics to incorporate the effects of baryon current, a nonvanishing chemical potential, and a realistic equation of state. Starting from a microscopic quantum theory, we employ a quasiparticle approximation to describe the evolution of hydrodynamic degrees of freedom and establish its connection to the Wigner formalism. Using methods from relativistic kinetic theory, we perform a second-order expansion to derive a closed set of equations for the components of the stress-energy tensor and the baryon current. The resulting transport coefficients, which depend on the equation of state, are obtained through a unified prescription that ensures thermodynamic consistency.

In previous work we have combined the ${\pi }^{-}{\pi }^0$, $2{\pi }^{-}{\pi }^{+}{\pi }^0$, and ${\pi }^{-}3{\pi }^0$ spectral data obtained from hadronic $\tau$ decays measured by the ALEPH and OPAL experiments, together with electroproduction data for several of the subleading hadronic modes and BABAR data for the $K\overline{K}$ mode to construct an inclusive nonstrange vector spectral function entirely based on experimental data, with no Monte-Carlo generated input. In this paper, we include, for the first time, the Belle $\tau \to {\pi }^{-}{\pi }^0{\nu }_{\tau }$ high-statistics decay data to construct a new inclusive nonstrange vector spectral function that combines more of the world’s available data. As no Belle data are at present available for the two $4\pi$ modes, this requires a revised data analysis in comparison with our previous work. From the resulting new spectral function, we obtain a new determination of the strong coupling, ${\alpha }_s$, using our previously developed strategy based on finite-energy sum rules. We find, at the $Z$ mass scale, ${\alpha }_s(m_Z^2)=0.1159(14)$. We discuss the smaller central value and larger error of our new result compared to our previous result, showing the shifts to be due mainly to significant changes in updated HFLAV results for the ${\pi }^{-}3{\pi }^0$ decay mode.

We study the $z_g$ distribution for heavy flavor, i.e., bottom and charm quark, jets propagating through the dense QCD medium. We extend the late emission approximation for the Armesto-Salgado-Wiedemann formula to heavy flavors. We consider both the normalized and $N_{\text{jet}}$ normalized $z_g$ distributions, and the ratio of the latter distributions to the vacuum ones, called the R ratio. We demonstrate that since there is no collinear singularity in the medium, there is no principal need to use the Sudakov safety technique for medium-induced emission. We see that contrary to the vacuum case, the normalized $z_g$ distribution is sensitive to the dead-cone angle value. In particular, for the case of the $N_{\text{jet}}$ normalized distribution with ${\theta }_g\le {\theta }_{\mathrm{cut}}$, it is possible to directly probe the dead-cone gluons in the medium. Our results can be useful to guide the experimental measurements of the heavy flavor jet substructure in a dense QCD medium.

Using the color dipole picture for photon-nucleus interactions at small $x$ together with the color glass condensate (CGC) effective theory, we demonstrate that the next-to-leading (NLO) order corrections to the cross section for the inclusive production of a pair of hard jets encode not only the Jalilian-Marian, Iancu, McLerran, Weigert, Leonidov and Kovner (JIMWLK) evolution with decreasing $x$, but also the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution of the gluon distribution function and the Collins-Soper-Sterman (CSS) evolution of the gluon transverse momentum dependent (TMD) distribution. The emergent CSS equation takes the form of a rate equation describing the evolution of the dijet distribution in the transverse momentum imbalance $K_{\perp }$ when increasing the dijet relative momentum $P_{\perp }$. All three types of evolution become important when both $P_{\perp }$ and $K_{\perp }$ are much larger than the nuclear saturation momentum $Q_s(x)$ and we propose a framework which encompasses all of them. The solution to the JIMWLK equation provides the source term for the DGLAP evolution with increasing $K_{\perp }$, which in turn generates the initial condition for the CSS evolution with increasing $P_{\perp }$.