The in-medium masses of the pseudoscalar open charm ($D$, $\overline{D}$, $D_s$ and $\overline{D_s}$) and open bottom ($B$, $\overline{B}$, $B_s$ and $\overline{B_s}$) mesons in hot asymmetric strange hadronic matter are studied within a QCD sum rule approach. These are computed using the medium modifications of the light quark condensates ($⟨\overline{q_i}{q}_i⟩$, with $(q_i,i=1,2,3)\equiv (u,d,s)$), the scalar gluon condensate, $⟨\frac{{\alpha }_s}{\pi }{G}_{\mu \nu }^a{G^a}^{\mu \nu }⟩$, the twist-2 tensorial gluon operator, $⟨\frac{{\alpha }_s}{\pi }(G_{\mu \sigma }^a{{G^a}_{\nu }}^{\sigma }{u}^{\mu }{u}^{\nu }-\frac{1}{4}{G}_{\mu \sigma }^a{G^a}^{\mu \sigma })⟩$ (where $u^{\mu }$ is the four-velocity of the medium) and other operators in the operator product expansion up to mass dimension 5. Within a chiral SU(3) model, the quark condensates are obtained from the medium modifications of the nonstrange and strange scalar-isoscalar fields ($\sigma$ and $\zeta$), and the scalar-isovector field, $\delta$, whereas, the gluon (scalar and twist-2) condensates are computed from the in-medium value of the dilaton field, $\chi$, which is incorporated within the chiral model to mimic the broken scale invariance of QCD. The mixed quark-gluon condensate $⟨\overline{q_i}{g}_s\sigma ·G{q}_i⟩$ is calculated from the in-medium quark condensate $⟨\overline{q_i}{q}_i⟩$. The splittings of the masses of the $D-\overline{D}$ ($B-\overline{B}$), as well as $D_s-\overline{D_s}(B_s-\overline{B_s})$ in the hadronic medium are due to the odd part of the spectral function. For the strange-charm (strange-bottom) mesons ($(q_i,i=3)\equiv s$), the value of $⟨{q_i}^{†}{q}_i⟩$ dominates over the contributions from the other operators, $⟨{q_i}^{†}i{D}_0^2{q}_i⟩$ and $⟨{q_i}^{†}{g}_s\sigma .G{q}_i⟩$, of the odd part of the spectral function. This is observed as opposite behavior of the particle-antiparticle mass splittings with the mass of the particle to be larger (smaller) than the antiparticle mass in nuclear (hyperonic) matter. The density and isospin asymmetry effects are observed to be the dominant medium effects which might have observable consequences on the production of charmonia and open charm mesons, and, on the production ratios, $D^{+}/D^{-}$ and $D^0/\overline{D^0}$, in asymmetric heavy ion collisions in the Compressed Baryonic Matter experiment at FAIR at the future facility at Gesellschaft für Schwerionenforschung (GSI).

We investigate new contributions to the $HZZ$ vertex from the flavor changing neutral current (FCNC) involving the Higgs and $Z$ bosons. Our calculations reveal that the form factors $h_2^V$ and $h_3^V$ ($V=H$, $Z$) can be induced through these couplings, and we present our results in terms of the Passarino-Veltman scalar functions. Using the current limits on $H\overline{t}c$ and $Z\overline{t}c$ couplings, we determine that the new contributions to the $CP$-conserving form factor $h_2^V$ are small compared to the Standard Model (SM) predictions. However, for the $CP$-violating form factor $h_3^V$, the contributions can reach values as high as ${10}^{-6}$, 5 orders of magnitude larger than in the SM. Furthermore, we examine how these results influence the left-right asymmetries in the processes $H^{*}\to ZZ$ and $Z^{*}\to ZH$. Our findings suggest that significant deviations from SM predictions may occur when considering FCNC contributions.

Quantum contextuality refers to the impossibility of assigning a predefined, intrinsic value to a physical property of a system independently of the context in which the property is measured. It is, perhaps, the most fundamental feature of quantum mechanics. The many states with different spin that particle physics provides are the ideal setting for testing contextuality. We verify that the polarization states of single spin-1 massive particles produced at colliders are contextual. We test $W^{+}$ gauge bosons produced in top-quark decays, $J/\psi$ and $K^{*}(892{)}^0$ mesons in $B$-meson decays and $\varphi$ mesons in ${\chi }_c^0$ and ${\chi }_c^1$ charmonium decays by reinterpreting the data and the analyses of the ATLAS, LHCb, Belle II and BESIII experimental collaborations, respectively. The polarization states of these four particles show contextuality with a significance larger than $5\sigma$. We also discuss the presence of quantum contextuality in spin states of bipartite systems formed by spin-$1/2$ particles. We test $\mathrm{\Lambda }$ and $\mathrm{\Sigma }$ baryons reinterpreting two BESIII data analyses, and pairs of top quarks utilizing a recent analysis of the CMS Collaboration. Quantum contextuality is present with a significance exceeding $5\sigma$ also in these cases. In addition, we study the feasibility of testing quantum contextuality by means of $Z$ boson production in association with the Higgs boson, $Z$ and $W$ bosons pairs created in Higgs boson decays and with pairs of $\tau$ leptons. For the latter, we use Monte Carlo simulations that mimic the settings of SuperKEKB and of future lepton colliders. Experiments at high energies, though not designed for the purpose, perform surprisingly well in testing for quantum contextuality.

We perform a comprehensive analysis of medium modifications on ungroomed jet angularities, ${\tau }_a$, within the framework of soft-collinear effective theory with Glauber gluons (${\mathrm{SCET}}_{\mathrm{G}}$). Angularities are a one-parameter family of jet substructure observables with angularity exponent $a<2$ for infrared safety. Variation of the angularity exponent allows one to modify the relative weighting of the collinear-to-soft radiations in the jet, thereby giving access to different moments of the jet transverse momentum spectrum. In this article, we focus on $a<1$ and provide detailed results for $a=-1$, 0, and 0.5. Within ${\mathrm{SCET}}_{\mathrm{G}}$, the interactions between jet and medium constituents are mediated by off-shell Glauber gluons generated from the color sources in the medium. While medium modifications are incorporated into the jet function via the use of medium-induced splitting functions, the soft function remains unmodified for $a<1$. For all values of $a$, we find that compared to jets in vacuum, the medium-modified distributions are shifted towards smaller values of jet angularity and have a steeper fall. This redistribution of the ungroomed angularity spectrum is more apparent for a jet with a larger cone size and for higher values of $a$. We also present results for the medium sensitivity towards $p_T$ of the jet and for a jet initiated in a less central event (10%–30% centrality). Finally, we provide the ratios of nucleus-nucleus and proton-proton differential angularity distributions for different angularity exponents and for two values of the jet radius parameter.

Theoretical understanding of deep learning remains elusive despite its empirical success. In this study, we propose a novel “synaptic field theory” that describes the training dynamics of synaptic weights and biases in the continuum limit. Unlike previous approaches, our framework treats synaptic weights and biases as fields and interprets their indices as spatial coordinates, with the training data acting as external sources. This perspective offers new insights into the fundamental mechanisms of deep learning and suggests a pathway for leveraging well-established field-theoretic techniques to study neural network training.

In this work, we study quantum chaos in a variety of holographic QCD models at finite temperature and chemical potentials. This includes the 1 and 2 $R$-charge black hole models, a potential reconstruction-based analytic bottom-up model, and a numerical bottom-up model. All these models are different avatars of the Einstein-Maxwell-dilaton gravity action, distinguished by their specific choices of dilaton potentials and gauge-kinetic coupling functions. We focus on computing the chaos parameter, the butterfly velocity, using three distinct methods: entanglement wedge reconstruction, out-of-time-ordered correlators, and pole skipping. We show that all three methods yield identical results for the butterfly velocity across all the holographic QCD models considered, further establishing the equivalence between the three approaches. Furthermore, we analyze in detail the behavior of the butterfly velocity as a function of chemical potential and temperature. Interestingly, a universal trend emerges across all models: the butterfly velocity increases/decreases with temperature/chemical potential for thermodynamically stable phases. Additionally, in the high-temperature limit, the butterfly velocity in all models approaches that of the chargeless plasma.

Using AdS/CFT methods in various holographic confining backgrounds, we present the connections between the behaviors of string scattering amplitudes and mutual information. We specifically lay down the analogies between the logarithmic branch cut behavior of the string scattering amplitude in $4d$, ${\mathcal{A}}_4$, at low and medium Mandelstam variable $s$, which is due to the dependence of the string tension on the holographic radial coordinate, and the branch cut behavior observed in mutual information and critical distance $D_c$ at low cut-off variable $u_{KK}$. In both cases, as $s$ or $u_{KK}$ increases, the peaks of the branch cuts fade away in the form of $\mathrm{Re}[{\mathcal{A}}_4]\propto s^{-1}$. Next, the modular flow and modular Hamiltonian as the intermediate quantities will be used to further shed light on this connection. We then explain how mutual information itself can act as a probe of chaos in various scenarios. For two examples of Compton scattering (of a photon entangled with another photon off a target) and also the decay of a highly excited string into two tachyons, the pattern of entanglement entropy and the change in the mutual information will be examined. Finally, the kink-kink and kink-antikink scatterings, as simple models of scattering in confining geometries, are employed to probe the fractal structures in the scatterings of topological defects.

We apply the variational Monte Carlo method based on neural network quantum states, using a neural autoregressive flow architecture as our ansatz, to determine the ground state wave function of the bosonic $\mathrm{SU}(N)$ Yang-Mills-type two-matrix model at strong coupling. Previous literature hinted at the inaccuracy of such an approach at strong coupling. In this work, the accuracy of the results is tested using lattice Monte Carlo simulations: we benchmark the expectation value of the energy of the ground state for system sizes $N$ that are beyond brute-force exact diagonalization methods. We observe that the variational method with neural network states reproduces the right ground state energy when the width of the network employed in this work is sufficiently large. We confirm that the correct result is obtained for $N=2$ and 3, while obtaining a precise value for $N=4$ requires more resources than the amount available for this work.

We analyze quantum parameter estimation by studying the dynamics of the quantum Fisher information (QFI) for two classes of parameters, acceleration and initial-state weight, in an Unruh-DeWitt detector undergoing four distinct noninertial motions: linear, cusped, catenary, and circular trajectories, respectively. We assume that the detector is initialized in a pure superposition state with a weight parameter $\theta$ characterizing the probability of the detector occupying each state. Our results reveal that, over long evolution times, the QFI for the acceleration parameter converges to a nonnegative asymptotic value that depends sensitively on the trajectory, whereas the QFI for the weight parameter decays to zero as the system thermalizes. Importantly, for sufficiently large accelerations, one can attain the optimal precision in estimating the acceleration parameter within a finite interaction time, eliminating the need for infinitely long measurements. Comparing trajectories, we find that for small accelerations (relative to the detector’s energy gap), linear motion yields the highest QFI for $\theta$, while for large accelerations, circular motion becomes optimal for estimating $\theta$. By contrast, circular motion offers the best precision for estimating acceleration itself in both the small- and large-acceleration regimes (the latter only at very long times). These contrasting behaviors of QFI across trajectories suggest a novel metrological protocol for inferring the underlying noninertial motion of a quantum probe.

Like general relativity, metric-affine gravity should be a viable effective quantum theory; otherwise, it is a mathematical curiosity without physical application. Assuming a perturbative quantum field theory, the universal, flat limit of metric-affine gravity offers a good foundation for model-building only when symmetry constraints are themselves sufficient to get rid of ghosts and tachyons in the spectrum of propagating particle states, without requiring any further tuning of the couplings. Using this symmetry-first criterion, we find that for parity-preserving models with a totally symmetric distortion, only massless spin-one and spin-three modes are possible besides the graviton. Moreover, no viable models result from gauge symmetries generated by a scalar field.

This paper studies axial gravitational perturbations of a uniform-density star in scalar-Einstein-Æther theory. By applying the Israel junction conditions explicitly in the presence of a scalar field minimally coupled to the gravitational sector, it is shown that a nontrivial scalar profile cannot be sustained, as it induces a divergence at the stellar center. Since analytical solutions are unattainable, the background metric is determined through numerical integration for a few representative configurations. For axial gravitational perturbations, it is found that the system of equations of motion cannot be decoupled as long as the Æther parameter $c_i$ does not vanish. Subsequently, the dynamics of the system can be simplified to two coupled equations that describe vector and tensor perturbations with distinct wave velocities $c_V$ and $c_T$, giving rise to a bimodal system. It is shown that as the stellar radius is smaller than that of the maximum of the vacuum Schwarzschild-type effective potential, a potential well is formed, leading to the emergence of echo phenomenon for the axial gravitational perturbations. When the stellar radius exceeds the could-have-been maximum, the resulting effective potential decreases monotonically, and the wave propagation is primarily dictated by the discontinuity occurring at the star’s surface, producing a type of more attenuated echo waves. In addition, we explore the specific properties of the resultant bimodal medium consisting of two degrees of freedom with distinct sound speeds. However, it is understood that such a characteristic does not lead to observational implications, and subsequently hardly offers a potential empirical means to constrain specific metric parameters of the Einstein-Æther. We present numerical calculations and discuss the potential implications of our findings.

Gravitational wave (GW) signals from extreme mass ratio inspirals (EMRIs) are a key observational target for the Laser Interferometer Space Antenna (LISA). The waveforms may be affected by the astrophysical environment surrounding the central black hole (BH), and in particular by the surrounding dark matter (DM) distribution. In this work, we consider the effect of a rotating DM “spike” around a central Kerr BH, and assess its detectability with LISA. Using a fully relativistic model for the rotating spike, we investigate its effect on the inspiral and hence on the emitted GW signals. We compute dephasings and mismatches to quantify how the spin of the primary BH affects the binary dynamics and the gravitational waveform. We show that the modifications due to the spin of the primary BH improve the detection prospects of DM spikes with LISA, and must be taken into account for future parameter estimation studies. We also estimate within post-Newtonian theory how the environment affects the background metric, and show that this effect is mostly negligible for the systems we consider.

Decaying dark matter (DDM) has emerged as an interesting framework to extend the $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) model, as many particle physics models predict that dark matter may not be stable over cosmic time and can impact structure formation. In particular, a model in which DM decays at a rate $\mathrm{\Gamma }$ and imprints a velocity kick $v$ onto its decay products leads to a low amplitude of fluctuations, as quantified by the parameter $S_8$, in better agreement with that measured by some past weak lensing surveys. Bayesian analyses have provided mixed conclusions regarding its viability, with a reconstructed clustering amplitude only slightly below the standard $\mathrm{\Lambda }\mathrm{CDM}$ value. In this paper, we contrast previous results with a frequentist analysis of Planck and SDSS baryon acoustic oscillation data. We find that the 68% confidence level region corresponds to a decay half-life of ${6.93}_{-2.85}^{+7.88}\mathrm{Gyr}$ and a velocity kick of ${1250}_{-1000}^{+1450}\mathrm{km}/\mathrm{s}$. These $1\sigma$ constraints strongly differ from their Bayesian counterparts, indicating the presence of volume effect in the Bayesian analysis. Moreover, we find that under the DDM model, the frequentist analysis predicts lower values of $S_8$, in agreement with those found by KiDS-1000 and DES-Y3 at $\sim 1.5\sigma$. We further show that previously derived KiDS-1000 constraints that appeared to exclude the best-fit model from Planck data were driven by priors on the primordial amplitude $A_s$ and spectral index $n_s$. When those are removed from the analysis, KiDS-1000 constraints on the DDM parameters are fully relaxed. It is only when applying Planck-informed priors on $A_s$ and $n_s$ to the KiDS-1000 analysis that one can constrain the model. We further highlight that in the absence of such priors, the region of scales best measured by KiDS-1000 does not exactly match the $S_8$ kernel (centered around $k\sim 0.1h/\mathrm{Mpc}$), but rather a slightly smaller range of scales centered around $k\sim 0.3h/\mathrm{Mpc}$. One must thus be careful in applying $S_8$ constraints to a model instead of the full data likelihood.

When fits of the same physical model to two different datasets disagree, we call this tension. Several apparent tensions in cosmology have occupied researchers in recent years, and a number of different metrics have been proposed to quantify tension. Many of these metrics suffer from limiting assumptions, and correctly calibrating these is essential if we want to successfully determine whether discrepancies are significant. A commonly used metric of tension is the evidence ratio $R$. The statistic has been widely adopted by the community as a Bayesian way of quantifying tensions, however, it has a nontrivial dependence on the prior that is not always accounted for properly. We show that this can be calibrated out effectively with neural ratio estimation. We demonstrate our proposed calibration technique with an analytic example, a toy example inspired by 21-cm cosmology, and with observations of the baryon acoustic oscillations from the Dark Energy Spectroscopic Instrument (DESI) and the Sloan Digital Sky Survey (SDSS). We find no significant tension between DESI and SDSS.

Some recent studies based on numerical relativity simulations claim that slow contraction/ekpyrosis is strongly preferred over inflation as the smoothing mechanism that brought the Universe into the homogeneous, isotropic, and flat state we observe today on large scales. In this paper, we evaluate the likelihood of the initial conditions employed in the aforementioned simulations by estimating the probability that a free scalar field dominating the Universe at the beginning of inflation or ekpyrosis will be sufficiently homogeneous on scales comparable to the Hubble radius at that time. We explore the space of parameters that characterize the initial power spectrum of the scalar field, finding that either can be more likely than the other for a fixed choice of parameters. On the other hand, when we extremize over these parameters, we find that the maximal probability for inflation is much higher than that of ekpyrosis.

We show that it is possible to simulate realistic inhomogeneities during cosmological inflation with high precision using numerical relativity. Stochastic initial conditions are set in line with the Bunch-Davies vacuum and satisfy the Hamiltonian and Momentum constraints of general relativity to leading order in perturbation theory. The subsequent fully nonlinear dynamical evolution is formulated within a family of geodesic gauges but can, in principle, be adapted to any choice of coordinates. We present three examples of inflationary dynamics: a simple quadratic potential, a potential with an inflection point, and a strong resonance model. When perturbations are small, we recover standard predictions of cosmological perturbation theory, and we quantify strongly nonlinear inhomogeneities when nonperturbative configurations emerge, such as in the strong resonance model. Our results pave the way toward the first realistic nonperturbative and fully nonlinear numerical relativity simulations of the early inflationary universe.

This study presents the impact of future measurements of deeply virtual Compton scattering (DVCS) with the ePIC detector at the electron-ion collider (EIC), currently under construction at Brookhaven National Laboratory. The considered process is sensitive to generalized parton distributions (GPDs), the understanding of which is a cornerstone of the EIC physics program. Our study marks a milestone in the preparation of DVCS measurements at EIC and provides a reference point for future analyses. In addition to presenting distributions of basic kinematic variables obtained with the latest ePIC design and simulation software, we examine the impact of future measurements on the understanding of nucleon tomography and DVCS Compton form factors, which are directly linked to GPDs. We also assess the impact of radiative corrections and background contribution arising from exclusive ${\pi }^0$ production.

It has been proposed to search for thermal and collective properties arising from parton-fragmentation processes by examining high jet charged-constituent multiplicities ($N_{\mathrm{j},\mathrm{ch}}$) in proton-proton (pp) collisions. This proposal was initially tested using the pythia 8event generator with the Monash tune, which incorporates multiparton interactions (MPI) and the MPI-based color reconnection (CR) model. These studies did not reveal any conclusive evidence for the presence of radial flow. In this paper, we expand upon the proposed Monte Carlo study by eliminating selection biases associated with triggering on charged particle multiplicities. Furthermore, MPI are disabled to focus exclusively on jet fragments. We analyze pp collisions at $\sqrt{s}=13\mathrm{TeV}$ simulated with pythia 8, exploring different implementations of the generator: thermodynamical string fragmentation and the standard Lund fragmentation model. The impact of color-string junctions was also explored. Surprisingly, the thermodynamical string fragmentation together with the close-packing of strings mechanism predicts a hint of baryon enhancement in jets. Additionally, the light-flavor baryon-to-meson ratios as a function of $j_{\mathrm{T}}$ exhibit similarities across all pythia 8 implementations, and hint at radial flow-like effects. In contrast, the ratio of heavy-flavor hadrons (${\mathrm{\Lambda }}_{\mathrm{c}}^{+}/{\mathrm{D}}^0$) at low $j_{\mathrm{T}}$ as a function of $N_{\mathrm{j},\mathrm{ch}}$ shows a trend similar to that observed as a function of charged-particle multiplicity in minimum-bias data, suggesting that color-string junctions may play a crucial role in heavy baryon production in jets. The same mechanism also predicts a $j_{\mathrm{T}}$-integrated ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}/{\mathrm{D}}^0$ ratio that increases with increasing $N_{\mathrm{j},\mathrm{ch}}$. Interestingly, for the lowest $N_{\mathrm{j},\mathrm{ch}}$ value, such a ratio is consistent with the ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$ limit, suggesting that jet multiplicity is a potential way to explore more dilute systems covering the multiplicity gap between ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$ and pp collisions.

There are only six independent types of symmetry-constrained (renormalizable) scalar potentials in the two Higgs doublet model (2HDM). For example, the scalar sector symmetry known as ${\mathbb{Z}}_2\otimes {\mathrm{\Pi }}_2$, generated by the simultaneous application of two independent symmetries acting on the scalar fields, and the generalized $CP$ symmetry known as GCP2 yield equivalent 2HDM scalar potentials. A similar situation arises for the scalar sector symmetries known as $\mathrm{U}(1)\otimes {\mathrm{\Pi }}_2$ and GCP3, respectively. In this paper, we show that this “degeneracy” remains when the definitions of the corresponding symmetries are extended to the Yukawa sector with three quark generations. The proof involves the exploration of all possible extensions of the corresponding symmetries to the Yukawa sector, consistent with the phenomenological constraints of nonzero quark masses and a nontrivial quark mixing matrix. Moreover, we find that this result is a peculiarity of a Yukawa sector with three quark generations. In particular, with two quark generations, we find that models based on the extension of ${\mathbb{Z}}_2\otimes {\mathrm{\Pi }}_2$ to the Yukawa sector are inequivalent with those based on GCP2.

Generic constraints on dark photons are generally presented assuming they have Stueckelberg masses. These constraints are strengthened if instead the mass is due to the Higgs mechanism and the dark Higgs is light. First, we show that under reasonable assumptions on the origin of kinetic mixing $\epsilon$ and perturbativity, the strengthened constraints on $\epsilon$ cannot be arbitrarily relaxed by making the Higgs heavy. Second, we demonstrate a simple mechanism for generating dark photon dark matter after inflation, where fluctuations of a dark Higgs by stochastic misalignment can produce stable dark photons through $h\to A^{\prime }{A}^{\prime }$ decay. Third, we point out new lower bounds on $\epsilon$ in the case where the dark photon mediates thermal freeze-out of light dark matter by $s$-channel exchange, taking account of generic expectations for the size of $\epsilon$, and astrophysical upper bounds on the self-interaction cross section.