We study heat conduction and momentum transport in the context of stochastic fluid dynamics. We consider a fluid described by model H in the classification of Hohenberg and Halperin. We study both noncritical and critical fluids, and we investigate transport properties in two as well as three dimensions. Our results are based on numerical simulations of model H using a Metropolis algorithm, and we employ Kubo relations to extract transport coefficients. We observe the expected logarithmic divergence of the shear viscosity in a two-dimensional noncritical fluid. At a critical point, we find that the transport coefficients exhibit power-law scaling with the system size $L$. The strongest divergence is seen for the thermal conductivity $\kappa$ in two dimensions. We find $\kappa \sim L^{x_{\kappa }}$ with $x_{\kappa }=1.6\pm 0.1$. The divergence is weaker in three dimensions, $x_{\kappa }=1.25\pm 0.3$, and the scaling exponent for the shear viscosity, $x_{\eta }$, is significantly smaller than $x_{\kappa }$ in both two and three dimensions.

By studying experimental data for invariant transverse momentum distribution $f(p_T)$ of hadrons in high energy $pp$, $p\mathrm{A}$, and AA collisions, we find two characteristic $p_T$ points relating to the behavior of ${[\ln f(p_T)]}^{\prime \prime }$, i.e., the second derivative of the logarithm of hadronic $p_T$ spectrum with respect to $p_T$. One point is $p_0$ at which ${[\ln f(p_T)]}^{\prime \prime }$ is zero and another point is $p_1$ at which ${[\ln f(p_T)]}^{\prime \prime }$ reaches maximum. The hadronic distribution can be classified into three kinetic regions, i.e., soft region $0<p_T<p_0$ dominated by hadrons from the soft parton system, hard region $p_T>p_1$ dominated by hadrons from high energy partonic jets, and the transition region $p_0<p_T<p_1$ of above two sources of hadron production. Using rich data of hadronic $p_T$ spectra at RHIC and LHC, we carry out a systematical analysis for $p_0$ and $p_1$ of kaon, $K^{*}$, $\varphi$, and baryons such as $p$, $\mathrm{\Lambda }$, $\mathrm{\Xi }$, $\mathrm{\Omega }$ in $pp$, $p$-Pb, and heavy-ion collisions, and show their dependence on hadron species, collision energy, collision centrality, and/or charged-particle multiplicity. We also study the correlation between $p_0$ of hadrons and their average transverse momentum $⟨p_T⟩$, and find a difference between $p_0-⟨p_T⟩$ correlation of baryons and that of mesons, which can be understood by the quark combination mechanism at hadronization. The systematic comparison for $p_0-⟨p_T⟩$ correlation of kaon, $\varphi$, $p$, and $\mathrm{\Lambda }$ in $pp$, $p$-Pb, Pb-Pb, and $\mathrm{Au}+\mathrm{Au}$ collisions at RHIC and LHC energies indicates that $p_0$ is a sensitive physical quantity of reflecting the production property of soft hadrons in high energy collisions.

We consider inclusive $\psi (2S)$ production in proton-proton collisions at collider energies in the framework of nonrelativistic QCD and high energy factorization beyond the low-order approximation. We utilize a matching scheme proposed earlier to merge the leading-order and tree-level next-to-leading-order (NLO) production amplitudes and now extend it to low transverse momenta and/or forward rapidities. With the improved scheme, we examine the possibility to simultaneously describe all unpolarized LHC data in the full kinematic range accessible to experimental measurements and try different transverse momentum-dependent gluon distributions in the proton. A global fit to the data is carried out to extract the color octet long-distance matrix elements for $\psi (2S)$ mesons. We show that taking the NLO corrections into account leads to a better description of the data.

Gauge theories can be solved exactly slightly away from the supersymmetric (SUSY) limit softly broken by anomaly mediation when the size of SUSY breaking is much smaller than the dynamical scale ($m\ll \mathrm{\Lambda }$). We show empirical evidence that the near-SUSY limit is continuously connected to the non-SUSY limit ($m\gg \mathrm{\Lambda }$) in $\mathrm{SU}(N_c)$ gauge theories with $N_f$ quarks in the fundamental representation. The evidence includes the behavior of quark bilinear condensate and gluon condensates, light hadron spectra, and consistency with the large $N_c$ limit including the Witten-Veneziano relations between the topological susceptibility and $m_{{\eta }^{\prime }}$ and $m_{\pi }$. In addition, we present new predictions when $N_f/N_c\gtrsim O(1)$.

We present a critical assessment of the present $B$ anomalies in the exclusive $b\to s\ell \ell$ mode based on the QCD factorization (QCDf) approach. In particular, we analyze the impact of different local form factor calculations and of the largest bin in the low-$q^2$ region. We also present a model-independent analysis of the new results of the LHCb and CMS experiments on the $B\to K^{*}{\mu }^{+}{\mu }^{-}$ angular observables. In addition, we update the global fit by including all $b\to s$ observables incorporating the new data from CMS and the LHCb. In these analyses, we use 10% or higher guesstimates of the nonfactorizable power corrections as additional uncertainties, serving as a placeholder for robust estimates of these contributions. Updating earlier results, we also analyze the combined LHCb and CMS data on the $B\to K^{*}{\mu }^{+}{\mu }^{-}$ angular observables using data-driven approaches to find indications of whether these tensions between the QCDf predictions and the present data are due to underestimated subleading hadronic contributions or due to new physics effects.

Neutron multiplicity is a key observable in recent neutrino experiments that can enhance the sensitivity of various neutrino physics searches. Nuclear deexcitation plays a significant role in neutron emissions associated with neutrino-nucleus interactions. Therefore, precise prediction of this process is essential. To address this need, a general-purpose nuclear deexcitation event generator nucdeex was developed and released as an open-source package. The treatment of low-lying discrete excited states was updated to better reproduce experimental data. Benchmarks were conducted using existing nuclear deexcitation event generators and experimental data. Application to other simulators, neutrino event generator neut and general particle simulation tool geant4, are also presented.

A search for flavor violating decays of the $Z$ boson to charged leptons is performed using data from proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ collected with the CMS detector at the LHC, corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$. Each of the decays $Z\to e\mu$, $Z\to e\tau$, and $Z\to \mu \tau$ is considered. The data are consistent with the backgrounds expected from standard model processes. For the $Z\to e\mu$ channel the observed (expected) 95% confidence level upper limit on the branching fraction is $1.9(2.0)\times {10}^{-7}$, which is the most stringent direct limit to date on this process; the corresponding limits for the $Z\to e\tau$ and $Z\to \mu \tau$ channels are $13.8(11.4)\times {10}^{-6}$ and $12.0(5.3)\times {10}^{-6}$, respectively. Additionally, the $e\mu$ final state is used to search for lepton flavor violating decays of $Z^{\prime }$ resonances in the mass range from 110 to $500\mathrm{GeV}$. No significant excess is observed above the predicted background levels.

Using data samples collected by the BESIII detector located at the Beijing Electron Positron Collider, the cross sections of the process $e^{+}{e}^{-}\to f_1(1285){\pi }^{+}{\pi }^{-}$ are measured at 45 center-of-mass energies from 3.808 to 4.951 GeV. An investigation on the energy-dependent cross section is performed, and no significant structure is observed.

We present a fully backreacted Einstein-Maxwell-Dilaton–flavor model with dynamical light and strange sectors, calibrated to lattice QCD using a machine-learning–assisted spectral method. The model reproduces the $2+1$-flavor equation of state and chiral dynamics with quantitative accuracy, and maps the Columbia plot with a tricritical point at $m_s^{\mathrm{tri}}\simeq 21\mathrm{MeV}$ and a critical mass $m_c\simeq 0.785\mathrm{MeV}$, consistent with lattice results. At finite density, it yields a crossover-to-first-order transition and predicts a critical endpoint at $T_C=75.4\mathrm{MeV}$ and ${\mu }_C=768\mathrm{MeV}$, within the reach of heavy-ion experiments. These findings establish a unified holographic framework for the QCD phase structure across quark masses and baryon density, providing the first consistent and quantitative description of both deconfinement and chiral transitions within a single holographic model.

Top quark electroweak interactions serve as a sensitive probe for beyond-Standard-Model physics, potentially exhibiting significant deviations from Standard Model predictions and offering crucial tests of fundamental symmetries in ultraviolet physics. This paper investigates their measurement through deep inelastic scattering (DIS) processes involving top quark loops at the Electron-Ion Collider (EIC), within the Standard Model effective field theory framework. We demonstrate that left-handed electron beam polarization can significantly enhance DIS cross sections for these interactions compared to right-handed scenario, highlighting the pivotal role of high polarization at the EIC in constraining these couplings. Compared to direct $pp\to t\overline{t}Z$ measurements at the Large Hadron Collider (LHC), DIS measurements could significantly improve these coupling constraints and effectively resolve parameter space degeneracies present in LHC data. Moreover, the expected precision from the EIC’s high-luminosity phase matches that of LEP electroweak precision measurements, underscoring the EIC’s significant potential to probe top quark properties.

We employ deep learning within holographic duality to investigate $T$-linear resistivity, a hallmark of strange metals. Utilizing physics-informed neural networks, we incorporate boundary data for $T$-linear resistivity and bulk differential equations into a loss function. This approach allows us to derive dilaton potentials in Einstein-Maxwell-dilaton-axion theories, capturing essential features of strange metals, such as $T$-linear resistivity and linear specific heat scaling. We also explore the impact of the resistivity slope on dilaton potentials. Regardless of slope, dilaton potentials exhibit universal exponential growth at low temperatures, driving $T$-linear resistivity and matching infrared geometric analyses. At a specific slope, our method rediscovers the Gubser-Rocha model, a well-known holographic model of strange metals. Additionally, the robustness of $T$-linear resistivity at higher temperatures correlates with the asymptotic Anti-de Sitter behavior of the dilaton coupling to the Maxwell term. Our findings suggest that deep learning could help uncover mechanisms in holographic condensed matter systems and advance our understanding of strange metals.

Dirac fermions, subject to external magnetic fields and in the presence of mass orders that assume topologically nontrivial spatial textures such as domain wall and vortices, for example, bind robust midgap states at zero energy, the number of which is governed by the Aharonov-Casher and Jackiw-Rebbi or Jackiw-Rossi index theorems, respectively. Here I extend the jurisdiction of these prominent index theorems to Lorentz invariant non-Hermitian (NH) Dirac operators, constructed by augmenting the celebrated Dirac Hamiltonian by a masslike anti-Hermitian operator that also scales linearly with momentum. The resulting NH Dirac operator manifests all-real eigenvalues over an extended NH parameter regime, characterized by a real effective Fermi velocity for NH Dirac fermions ($v_{\mathrm{F}}$). From the explicit solutions of the zero-energy bound states, I show that in the presence of external magnetic fields of arbitrary shape such modes always exist when the system encloses a finite number of magnetic flux quanta, while in the presence of spatially nontrivial textures of the mass orders localized zero-energy modes can only be found in the spectrum when $v_{\mathrm{F}}$ is real. These findings pave a concrete route to realize nucleation of competing orders from the topologically robust zero-energy manifold in NH or open Dirac systems. Possible extensions of these outcomes to other index theorems and tabletop experimental setups to test these predictions are discussed.

The gravitational wave (GW) signals from extreme mass-ratio inspirals (EMRIs), a key target for the Laser Interferometer Space Antenna (LISA), will be affected in the presence of dark matter (DM) halos. In this paper we explore whether the effects of DM are detectable by LISA within a fully relativistic framework. We model the massive EMRI component as a nonrotating black hole (BH) surrounded by a DM halo. We compute axial and polar GW fluxes for circular orbits at linear order in the mass ratio for DM density profiles with varying mass and compactness. By comparing the phase evolution with vacuum systems, we find that DM halos can induce dephasings of tens to hundreds of radians over a one-year observation period. We demonstrate that even highly diluted DM distributions can significantly affect the emitted waveforms, and that the resulting GW signals can usually be distinguished from each other. While it is important to generalize these findings to more generic orbits and to spinning BHs, our results suggest that LISA could not only reveal the presence of DM halos, but also discriminate between different halo models.

When numerically solving Einstein’s equations for binary black holes (BBH), we must find initial data on a three-dimensional spatial slice by solving constraint equations. The construction of initial data is a multistep process, in which one first chooses freely specifiable data that define a conformal background and impose boundary conditions. Then, one numerically solves elliptic equations and calculates physical properties such as horizon masses, spins, and asymptotic quantities from the solution. To achieve desired properties, one adjusts the free data in an iterative “control” loop. Previous methods for these iterative adjustments rely on Newtonian approximations and do not allow the direct control of total energy and angular momentum of the system, which becomes particularly important in the study of hyperbolic encounters of black holes. Using the spectre code, we present a novel parameter control procedure that benefits from Broyden’s method in all controlled quantities. We use this control scheme to minimize drifts in bound orbits and to enable the construction of hyperbolic encounters. We see that the activation of off-diagonal terms in the control Jacobian gives us better efficiency when compared to the simpler implementation in the Spectral Einstein Code. We demonstrate robustness of the method across extreme configurations, including spin magnitudes up to $\chi =0.9999$, mass ratios up to $q=50$, and initial separations up to $D_0=1000M$. Given the open-source nature of spectre, this is the first time a parameter control scheme for constructing bound and unbound BBH initial data is available to the numerical-relativity community.

In our previous work [R. Falcone and C. Conti, Phys. Rev. Res. 7, 033079 (2025).], we derived the metric tensor for cylindrically shaped pulses with uniform energy density. Building upon that framework, we derive the complete set of geodesics with zero angular velocity. We show that perturbations in particle trajectories may be observed in gamma ray bursts. Also, deviations in the motion of moving particles are significantly larger than those previously found for particles that are initially at rest.

We construct an exact solution in four-dimensional Einstein-Maxwell-dilaton theory describing multicentered rotating black holes carrying both electric and magnetic charges obtained via dimensional reduction from five-dimensional Einstein gravity. This generalizes the Majumdar-Papapetrou solution to the rotating case and extends the recent multicentered rotating black hole solutions of Teo and Wan to configurations with unequal electric and magnetic charges. The resulting spacetimes are free of curvature singularities, conical defects, Dirac-Misner strings, and closed timelike curves, both on and outside the horizons, provided that the black holes have either aligned or antialigned spin orientations.

We investigate observational signatures of ultralight vector dark matter with masses $m\sim {10}^{-24}–{10}^{-22}\mathrm{eV}$ in pulsar timing arrays, taking into account general polarization states of the vector field. We find that vector dark matter induces pulsar timing residuals with nontrivial directional dependence, reflecting the anisotropic property and polarization structure specific to vector dark matter, unlike scalar dark matter. We also derive angular correlation curves of the timing residuals. Intriguingly, circular polarization of the vector dark matter enhances the quadrupole nature of the correlation curve, resulting in a more notable bending of the Hellings-Downs curve. The derived correlation curves offer a useful means to distinguish gravitational wave and dark matter contributions and to probe the nature of dark matter.

Recent advances in cosmological simulations enable a detailed investigation of the structure of Milky Way–like galaxies, which form and evolve in a self-consistent manner within these simulations. Using a publicly available sample of such models from Illustris TNG50, we conducted a comprehensive analysis of their dynamical structure, focusing on the contributions of individual components (e.g., bulge, disk, dark halo) to the rotation curve. This allowed us to further refine the sample by selecting only those models that best match the rotation curve data of our Galaxy, resulting in a subset of 12 galaxy models. For each model, we calculated a triplet of actions ($J_{\mathrm{R}}$, $J_z$, $L_z$) and the adiabatic invariant $J_v=J_{\mathrm{R}}+J_z+|L_z|/2$ for each stellar particle comprising such systems. We found that the two-dimensional $(L_z,J_v)$ maps for all barred models consistently exhibit a distinct thin or thick stripe associated with the bar. In some cases, a counterrotating component characterized by $L_z<0$ and/or a roughly axisymmetric vertically extended component appearing above the bar stripe in action space are observed. By comparing the actual contributions of individual components to those derived from standard rotation curve decomposition techniques, we found that the dark matter halo in the considered cosmological models is more concentrated than typical Navarro-Frenk-White profiles and instead follows a pseudoisothermal profile, while the stellar component is overall less massive. Separating the bar from the disk via actions, we obtained that the bulge, which effectively represents the bar while decomposing the rotation curve, is found to be approximately one and a half times as massive as the actual bar component.

We investigate how primordial magnetic fields (PMFs) affect the formation kinetics of the first molecules, ${\mathrm{H}}_2$, HD, and ${\mathrm{HeH}}^{+}$, as well as the populations of rovibrational levels and the global signals in the rovibrational transitions of ${\mathrm{H}}_2$ and HD. For this purpose, we numerically solve a system of differential equations that describes the gas energy balance, the kinetics of the formation of the first molecules, and the populations of their rovibrational levels, taking into account the PMF energy dissipation through ambipolar diffusion and decaying turbulence. We show that PMFs can significantly speed up the formation and destruction of the first molecules, leading to an increase in the number density of ${\mathrm{H}}_2$ and HD molecules and a decrease in the number density of ${\mathrm{HeH}}^{+}$ ion molecules compared to the case without PMFs. We demonstrate that more frequent collisions of the gas particles in such models alter the ortho-to-para ratio of hydrogen molecules, making it a potential probe of the thermal history of gas in the early Universe. In contrast to the standard cosmological model, where the global signal from the first molecules appears as an absorption feature in the cosmic microwave background spectrum, cosmological models with PMFs can produce an emission signal. Specifically, for nonhelical PMFs with $n_B=-2.9$ and a strength of $\sim 1\mathrm{nG}$, the signal transforms into emission with an amplitude of about $\sim 0.5\mathrm{Jy}/\mathrm{s}\mathrm{r}$. This signal is comparable in magnitude to other known cosmic microwave background spectral distortions and falls within the detection capabilities of several proposed missions, including Super-PIXIE, Multi-SIMBAD (four units), and Voyage2050. We show that both the amplitude and the spectral range of the global signals from the first molecules are highly sensitive to the spectral index $n_B$, the strength $B_0$, and the helicity of the PMFs. Therefore, the global signals from the first molecules can serve as a potential probe of PMFs.

Within the framework of the thermal soft-wall model of AdS/QCD, we investigate phenomenological properties of pions at finite temperature. This includes the electromagnetic form factor $F_{\pi }(Q^2,T)$, the thermal mass $M_{\pi }(T)$, charge radius $r_{\pi }(T)$, the generalized parton distribution (GPD) $H_{\pi }(x,Q^2,T)$, the charge density ${\rho }_{\pi }(b,T)$ of the pion, the pion-nucleon coupling constant $g_{\pi NN}(T)$, and pion-$\mathrm{\Delta }$ baryon coupling constant $g_{\pi \mathrm{\Delta }\mathrm{\Delta }}(T)$ coupling constant at finite temperature. The thermal pion form factor is extrapolated from the zero-temperature case. Subsequently, the GPD is obtained at finite temperature from this form factor. The above-mentioned quantities were analyzed using a thermal dilaton field in the five-dimensional anti–de Sitter action. Moreover, we determine the theoretical expression for the temperature-dependent pion-nucleon coupling constant, and the pion-$\mathrm{\Delta }$ baryon coupling constant using thermal profile functions of the nucleon, $\mathrm{\Delta }$ baryon and the pion. Our results show that the values of these quantities decrease with increasing temperature and vanish near the critical temperature $T_c$, except for the pion radius, which diverges at $T_c$. Our results reproduce expected features of low-energy hadron dynamics, thus validating the phenomenological utility of the thermal soft-wall model.