A new mechanism has been proposed to simultaneously explain the presence of dark matter and the matter-antimatter asymmetry in the Universe. This scenario predicts exotic $B$-meson decays into a baryon and a dark-sector antibaryon (${\psi }_D$) with branching fractions accessible at $B$ factories. We present a search for $B\to \mathrm{\Lambda }{\psi }_D$ decays using data collected by the BABAR experiment at SLAC. This reaction is identified by fully reconstructing the accompanying $B$ meson and requiring the presence of a single $\mathrm{\Lambda }$ baryon in the remaining particles. No significant signal is observed, and bounds on the $B\to \mathrm{\Lambda }{\psi }_D$ branching fraction are derived in the range $0.13–5.2\times {10}^{-5}$ for $1.0<m_{{\psi }_D}<4.2\mathrm{GeV}/c^2$. These results set strong constraints on the parameter space allowed by the theory.

Bigravity is one of the natural extensions of general relativity and contains an additional massive spin-2 field which can be a good candidate for dark matter. To discuss the production of spin-2 dark matter, we study fixed-point solutions of the background equations for axisymmetric Bianchi type-I universes in two bigravity theories without a Boulware-Deser ghost, i.e., Hassan-Rosen bigravity and the minimal theory of bigravity. We investigate the local and global stabilities of the fixed points and classify them. Based on the general analysis, we propose a new scenario where spin-2 dark matter is produced by the transition from an anisotropic fixed-point solution to an isotropic one. The produced spin-2 dark matter can account for all or a part of dark matter and can be directly detected by laser interferometers in the same way as gravitational waves.

We construct new classes of modified theories in which the matter sector couples with the Einstein tensor, namely we consider direct couplings of the latter to the energy-momentum tensor, and to the derivatives of its trace. We extract the general field equations, which do not contain higher-order derivatives, and we apply them in a cosmological framework, obtaining the Friedmann equations, whose extra terms give rise to an effective dark energy sector. At the background level we show that we can successfully describe the usual thermal history of the universe, with the sequence of matter and dark-energy epochs, while the dark-energy equation-of-state parameter can lie in the phantom regime, tending progressively to $-1$ at present and future times. Furthermore, we confront the theory with cosmic chronometer data, showing that the agreement is very good. Finally, we perform a detailed investigation of scalar and tensor perturbations, and extracting an approximate evolution equation for the matter overdensity we show that the predicted behavior is in agreement with observations.

We present new constraints on the masses of the halos hosting the Milky Way and Andromeda galaxies derived using graph neural networks. Our models, trained on 2,000 state-of-the-art hydrodynamic simulations of the CAMELS project, only make use of the positions, velocities and stellar masses of the galaxies belonging to the halos, and are able to perform likelihood-free inference on halo masses while accounting for both cosmological and astrophysical uncertainties. Our constraints are in agreement with estimates from other traditional methods, within our derived posterior standard deviation.

We show that nonstandard neutrino self-interactions can lead to total flavor equipartition in a dense neutrino gas, such as those expected in core-collapse supernovae. In this first investigation of this phenomenon in the multiangle scenario, we demonstrate that such a flavor equipartition can occur on very short scales, and therefore very deep inside the newly formed proto-neutron star, with a possible significant impact on the physics of core-collapse supernovae. Our findings imply that future galactic core-collapse supernovae can appreciably probe nonstandard neutrino self-interactions, for certain cases even when they are many orders of magnitude smaller than the Standard Model terms.

We consider a general two Higgs doublet model which can simultaneously solve discrepancies in neutral $B$ meson decay ($b\to s\ell \overline{\ell }$ distribution) and charged $B$ meson decay ($b\to c\tau \overline{\nu }$) with a charged Higgs. The model contains two additional neutral scalars at the same mass scale and predicts distinctive signals at the LHC. Based on the recent same-sign top search by the ATLAS collaboration, we found the constraint on the scalar mass spectrum. To probe the remaining mass window, we propose a novel $cg\to t\tau \overline{\tau }$ process at the LHC.

MUonE is a proposed experiment designed to measure the hadronic vacuum polarization contribution to muon $g-2$ through elastic $\mu -e$ scattering. As such, it employs an extremely high-resolution tracking apparatus. We point out that this makes MUonE also a very promising experiment to search for displaced vertices from light, weakly interacting new particles. We demonstrate its potential by showing how it has excellent sensitivity to dark photons in the mass range $10\mathrm{MeV}\le m_{A^{\prime }}\le 100\mathrm{MeV}$ and kinetic mixing parameter ${10}^{-5}\le \epsilon e\le {10}^{-3}$, through the process ${\mu }^{\pm }{e}^{-}\to {\mu }^{\pm }{e}^{-}{A}^{\prime }$ followed by $A^{\prime }\to e^{+}{e}^{-}$.

We propose a new way of probing the nonthermal origin of baryon asymmetry of the Universe (BAU) and dark matter (DM) from evaporating primordial black holes (PBHs) via stochastic gravitational waves (GWs) emitted due to PBH density fluctuations. We adopt a baryogenesis setup where $CP$-violating out-of-equilibrium decays of a colored scalar, produced nonthermally at late epochs from PBH evaporation, lead to the generation of BAU. The same PBH evaporation is also responsible for nonthermal origin of superheavy DM. Unlike the case of baryogenesis via leptogenesis that necessarily corners the PBH mass to $\sim \mathcal{O}(1)\mathrm{g}$, here we can have PBH mass as large as $\sim \mathcal{O}({10}^7)\mathrm{g}$ due to the possibility of producing BAU directly below sphaleron decoupling temperature. Because of the larger allowed PBH mass we can also have observable GW with mHz-kHz frequencies originating from PBH density fluctuations keeping the model constrained and verifiable at ongoing as well as near future GW experiments like LIGO, BBO, DECIGO, CE, ET etc. Because of the presence of new colored particles and baryon number violation, the model also has complementary detection prospects at laboratory experiments.

In extended Higgs models, a discrete symmetry is needed in the quark sector to avoid tree-level flavor-changing neutral currents. However, this is not necessarily the case in the lepton sector. We consider a model in which one Higgs couples to quarks and three others couple to the electron, muon, and tau, respectively. This four-doublet model is presented with the full scalar potential and the gauge and Yukawa couplings. The constraints from boundedness, perturbativity and oblique parameters are incorporated as well as constraints from meson-antimeson mixing, radiative $B$-decays, and the diphoton Higgs decay rate. We also consider bounds from searches for heavy neutral and charged scalars at the LHC. Since the Standard Model Higgs couplings match predictions very well, we focus on the alignment limit of the model. It is shown that for a wide range of parameters, the lightest additional scalar, pseudoscalar and charged scalar can have substantial decays into electrons and muons (in contrast to the usual leptonic decays into taus). An interesting signature in the neutral sector would be the production, through vector boson fusion, of a pair of scalars, each of which decays into an electron or muon pair.

Recent developments of a deep learning feed-forward network for estimating elliptic flow ($v_2$) coefficients in heavy-ion collisions have shown the prediction power of this technique. The success of the model is mainly the estimation of $v_2$ from final-state particle kinematic information and learning the centrality and transverse momentum ($p_{\mathrm{T}}$) dependence of $v_2$. The deep learning model is trained with Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$ minimum bias events simulated with a multiphase transport model. We extend this work to estimate $v_2$ for light-flavor identified particles such as ${\pi }^{\pm }$, ${\mathrm{K}}^{\pm }$, and $\mathrm{p}+\overline{\mathrm{p}}$ in heavy-ion collisions at RHIC and LHC energies. The number-of-constituent-quark scaling is also shown. The evolution of the $p_{\mathrm{T}}$-crossing point of $v_2(p_{\mathrm{T}})$, depicting a change in baryon-meson elliptic flow at intermediate $p_{\mathrm{T}}$, is studied for various collision systems and energies. The model is further evaluated by training it for different $p_{\mathrm{T}}$ regions. These results are compared with the available experimental data wherever possible.

We present the leading-order mixed-action effect ${\mathrm{\Delta }}_{\mathrm{mix}}\equiv m_{\pi ,\mathrm{vs}}^2-\frac{m_{\pi ,\mathrm{vv}}^2+m_{\pi ,\mathrm{ss}}^2}{2}$ using highly improved staggered quarks (HISQ), clover, or overlap valence fermion actions on gauge ensembles using various sea fermion actions across a widely used lattice spacing range $a\in [0.04,0.19]\mathrm{fm}$. The results suggest that ${\mathrm{\Delta }}_{\mathrm{mix}}$ decreases as the fourth order of the lattice spacing on the gauge ensembles with dynamical chiral sea fermions, such as domain wall or HISQ fermions. When a clover sea fermion action that has explicit chiral symmetry breaking is used in the ensemble, ${\mathrm{\Delta }}_{\mathrm{mix}}$ can be much larger regardless of the valence fermion action used.

We use the $\mathrm{complexity}=\text{volume}$ (CV) prescription to study the effect of a magnetic field on the computational complexity for states in the gauge theories dual to two different gravitational models. In one of these theories the complexity increases with the intensity of the magnetic field, while in the other a more interesting behavior is discovered, resulting in a phenomenon that we term magnetic simplification. The relevant difference between the two theories is that the content of the second includes a scalar operator with a nonvanishing vacuum expectation value. This leads us to conclude that the direct impact of the magnetic field is to increase the complexity of a state, but it can indirectly lower it by diminishing the complexity associated to additional degrees of freedom when these do not vanish across the space. We additionally compare the results obtained working in the full ten-dimensional backgrounds and in their effective five-dimensional truncations, exhibiting that the question is still current about which surface, whether the uplift of the 5D extremal hypersurface or the extremal surface in 10D, should be used in the CV prescription.

We explore the upper bound of the Lyapunov exponent for test particles that maintain equilibrium in the radial direction near the charged black brane with the hyperscaling violating factor. The influences of black brane parameters (hyperscaling violation exponent $\theta$ and dynamical exponent $z$) are investigated. We show that the equilibrium in the radial direction of test particles can violate the chaos bound. The chaos bound is more easily violated for the near-extremal charged black branes. When the null energy condition ($T_{\mu \nu }{\xi }^{\mu }{\xi }^{\nu }\ge 0$) is broken, the bound is also more likely to be violated. These results indicate that the chaos bound of particle motion is related to the temperature of the black hole and the null energy condition (NEC). By considering the zero-temperature and $T_{\mu \nu }{\xi }^{\mu }{\xi }^{\nu }=0$ cases, we obtain the critical parameters ${\theta }_c$ and $z_c$ for the violation of chaos bound. The chaos bound is always satisfied in the range $\theta >{\theta }_c$ or $z>z_c$.

We analyze the general structure of the three-point functions of conserved higher-spin supercurrents in 3D, $\mathcal{N}=1$ superconformal field theory. It is shown that supersymmetry imposes additional restrictions on correlation functions of conserved higher-spin currents. We develop a manifestly supersymmetric formalism to compute the three-point function $⟨{\mathbf{J}}_{s_1}{\mathbf{J}}_{s_2}^{\prime }{\mathbf{J}}_{s_3}^{\prime \prime }⟩$, where ${\mathbf{J}}_{s_1}$, ${\mathbf{J}}_{s_2}^{\prime }$, and ${\mathbf{J}}_{s_3}^{\prime \prime }$ are conserved higher-spin supercurrents with superspins $s_1$, $s_2$, and $s_3$, respectively (integer or half-integer). Using a computational approach limited only by computer power, we analytically impose the constraints arising from the superfield conservation equations and symmetries under permutations of superspace points. Explicit solutions for three-point functions are presented, and we provide a complete classification of the results for $s_i\le 20$; the pattern is very clear, and we propose that our classification holds for arbitrary superspins. We demonstrate that Grassmann-even three-point functions are fixed up to one parity-even structure and one parity-odd structure, while Grassmann-odd three-point functions are fixed up to a single parity-even structure. The existence of the parity-odd structure in the Grassmann-even correlation functions is subject to a set of triangle inequalities in the superspins. For completeness, we also analyze the structure of three-point functions involving conserved higher-spin supercurrents and scalar superfields.

By employing a free scalar quantum field theory model previously introduced [G. Peruzzo and S. P. Sorella, Phys. Rev. D 106, 125020 (2022)], we attempt to formulate the Bell-Clauser-Horne-Shimony-Holt (Bell-CHSH) inequality within the Feynman path integral. This possibility relies on the observation that the Bell-CHSH inequality exhibits a natural extension to quantum field theory in such a way that it is compatible with the time ordering $T$. By treating the Feynman propagator as a distribution and by introducing a suitable localizing set of compact support smooth test functions, we work out the path integral setup for the Bell-CHSH inequality, recovering the same results of the canonical quantization.

We investigate the evaporation of an uncharged and nonrotating black hole in vacuum by taking into account the effects given by the shrinking of the horizon area. These include the backreaction on the metric and other smaller contributions arising from quantum fields in curved spacetime. Our approach is facilitated by the use of an analog accelerating moving mirror. We study the consequences of this modified evaporation on the black hole entropy. Insights are provided on the amount of information obtained from a black hole by considering nonequilibrium thermodynamics and the nonthermal part of Hawking radiation.

Gravitational signatures of black hole superradiance are a unique probe of ultralight particles that are weakly coupled to ordinary matter. The existence of an ultralight boson would lead spinning black holes with size comparable to the Compton wavelength of the boson to become superradiantly unstable to forming an oscillating cloud, spinning down the black hole, and radiating gravitational waves in the process. However, maximizing the chance of observing such signals or, in their absence, placing the strongest constraints on the existence of such particles, requires accurate theoretical predictions. In this work, we introduce a new gravitational waveform model, superrad, that models the dynamics, oscillation frequency, and gravitational wave signals of these clouds by combining numerical results in the relativistic regime with fits calibrated to analytical estimates, covering the entire parameter space of ultralight scalar and vector clouds with the lowest two azimuthal numbers ($m=1$ and 2). We present new calculations of the gravitational wave frequency evolution as the boson cloud dissipates, including using fully general-relativistic methods to quantify the error in more approximate treatments. Finally, as a first application, we assess the viability of conducting follow-up gravitational wave searches for ultralight vector clouds around massive black hole binary merger remnants. We show that LISA may be able to probe vector masses in the range from $1\times {10}^{-16}$ to $6\times {10}^{-16}\mathrm{eV}$ using follow-up gravitational wave searches.

One of the few firm predictions of string theory is the existence of a massless scalar field coupled to gravity, the dilaton. In its presence, the value of the fundamental constants of the universe, such as the fine-structure constant, will vary with the time-dependent vacuum expectation value of this field, in direct violation of the Einstein equivalence principle. The runaway dilaton proposed by Damour, Piazza, and Veneziano provides a physically motivated cosmological scenario which reconciles the existence of a massless dilaton with observations, while still providing nonstandard and testable predictions. Furthermore, the field can provide a natural candidate for dynamical dark energy. While this model has been previously constrained from local laboratory experiments and low-redshift observations, we provide here the first full self-consistent constraints, also including high redshift data, in particular from the cosmic microwave background. We consider various possible scenarios in which the field could act as quintessence. Despite the wider parameter space, we make use of recent observational progress to significantly improve constraints on the model, showing that order unity couplings (which would be natural in string theory) are ruled out.

Scale dependence of fundamental physical parameters is a generic feature of ordinary quantum field theory. When applied to gravity, this idea produces effective actions generically containing a running Newtonian coupling constant, from which new (spherically symmetric) black hole spacetimes can be inferred. As a minimum useful requirement, of course, the new metrics should match with a Schwarzschild field at a large radial coordinate. By further imposing to the new scale dependent metric the simple request of matching with the Donoghue quantum corrected potential, we find a not yet explored black hole spacetime, which naturally turns out to describe the so-called Planck stars.