In this paper we found the parton densities at high energies. Their expressions stems from our attempts to reconcile the exact solution to the Balitsky-Kovchegov equation, which describes the rare fluctuation in the dipole-target scattering, with the fact that this equation sums the “fan” Pomeron diagrams. Using these densities we can calculate the contributions of large Pomeron loops to dipole-dipole scattering at high energies. We detected that the scattering matrix for this process has the same suppression as was predicted by Iancu and Mueller from their estimates of the “rare” fluctuation in QCD. Applying the Abramovsky, Gribov and Kancheli cutting rules we found that the produced gluons are distributed accordingly the Koba, Nielsen, and Olesen law that leads to the entropy $S_E=\ln (xG(x,Q^2))$. $xG$ has to be in the saturation region at high energies.

In collider experiments, an event is characterized by two distinct yet mutually complementary features: the “global features” and the “local features.” Kinematic information such as the event topology of a hard process, masses, and spins of particles comprises global features spanning the entire phase space. This global feature can be inferred from reconstructed objects. In contrast, representations of particles in gauge groups, such as quantum chromodynamics (QCD), offer localized features revealing the dynamics of an underlying theory. These local features, particularly observed in the patterns of radiation as raw data in various detector components, complement the global kinematic features. We propose a simple but effective neural network architecture that seamlessly integrates information from both kinematics and QCD to enhance the signal sensitivity at colliders.

Axion-mediated forces are enhanced by the presence of $CP$-violating axion couplings, which are however tightly constrained by electric dipole moment (EDM) searches. We discuss the underlying hypotheses behind different sources of $CP$ violation at high energies and the interplay between axion-mediated force experiments and EDM observables. Specifically, we identify various mechanisms, based on new sources of $CP$ violation or Peccei-Quinn symmetry breaking, that can significantly relax EDM constraints, leading to a substantial redefinition of the QCD axion window for axion-mediated forces. By considerably enlarging the QCD axion parameter space, our results provide a well-motivated target for experiments probing scalar axion couplings to matter fields. These include fifth-force tests of gravity, as well as searches for spin-dependent forces via precision magnetometry, proton storage rings and ultracold molecules.

$CP$ violation in neutral $B$ meson oscillations is an experimental observable that could be directly related to the baryon asymmetry of the Universe through the $B$-mesogenesis mechanism. As this phenomenon is highly suppressed in the Standard Model, it could also be a sensitive probe for many new physics scenarios that modify neutral meson mixing. Motivated by these facts, and the timely $B$ physics program at the LHC and Belle II, we analyze how large $CP$ violation in the mixing of neutral $B_d$ and $B_s$ meson systems could be. We answer this question, in light of current experimental data, within three different scenarios, namely: (i) generic heavy new physics only affecting the mass mixing $M_{12}^q$, (ii) vectorlike quark extensions that introduce deviations of $3\times 3$ CKM unitarity, and (iii) light new physics modifying the decay mixing ${\mathrm{\Gamma }}_{12}^q$. We find that enhancements of the semileptonic asymmetries, that measure the amount of $CP$ violation in mixing, at the level of ${10}^{-3}$ for the $B_d$ system and ${10}^{-4}$ for the $B_s$ system can be achieved within scenarios (i) and (ii), while they are much more suppressed in realistic UV completions triggering scenario (iii). With respect to cosmology, the difficulty of finding large $CP$ asymmetries in our analysis puts the $B$-mesogenesis mechanism in tension. Finally, we conclude that upcoming experimental searches for $CP$ violation in $B$ meson mixing at LHCb and Belle II are unlikely to detect a new physics signal for the most generic models.

We calculate the screening masses of pseudoscalar mesons in a hot and strongly magnetized medium within the framework of the SU(3) Nambu-Jona–Lasinio model, using a magnetic field-independent regularization scheme. Inverse magnetic catalysis (IMC) is implemented through the use of a magnetic field-dependent coupling $G(B)$, fitted to reproduce lattice quantum chromodynamics (QCD) results for the pseudocritical chiral transition temperature $T_c^B$. For the external homogeneous magnetic field considered, neutral screening masses separate in two types: perpendicular and parallel to the direction of the field, while for charged mesons only parallel energies can be defined for each Landau level. We obtain $m_{\mathrm{scr},\perp }>m_{\mathrm{scr},||}$, as expected from causality. Thermally, all screening energies are almost constant until some critical temperature, whose behavior is correlated with $T_c^B$. They rapidly increase around this value, keeping a steady enhancement afterward due to thermal excitation. Magnetically, neutral parallel masses are enhanced (suppressed) at high temperatures when considering $G(B)$ ($G$). Perpendicular ones display a nonmonotonic magnetic behavior for $G$ (due to increasing $T_c^B$) when $T\lesssim 500\mathrm{MeV}$, but become magnetically enhanced when $T\gtrsim 500\mathrm{MeV}$. For $G(B)$ they always increase with $B$. Charged parallel energies are always magnetically enhanced, for both couplings. In the high-temperature limit, we show that both neutral and charged screening energies converge to $2\pi T$. At $B=0$ the model overestimates the remaining quark interaction in this regime. At $B\ne 0$ we find that, when IMC is accounted for, the interaction is suppressed as $B$ increases, a fact that appears to be at odds with currently available lattice QCD results.

Based on $(10.09\pm 0.04)\times {10}^{9}J/\psi$ events collected with the BESIII detector operating at the BEPCII collider, a partial wave analysis of the decay $J/\psi \to \varphi {\pi }^0\eta$ is performed. We observe for the first time two new structures on the $\varphi \eta$ invariant mass distribution, with significances exceeding $27\sigma$ and $13\sigma$; the first with $J^{\mathrm{PC}}=1^{+-}$, mass $\mathrm{M}=(1908\pm 6(\mathrm{stat}){}_{-4}^{+8}(\mathrm{sys}))\mathrm{MeV}/c^2$, and width $\mathrm{\Gamma }=(175\pm 13(\mathrm{stat}){}_{-16}^{+7}(\mathrm{sys}))\mathrm{MeV}$, the second with $J^{\mathrm{PC}}=1^{--}$, mass $\mathrm{M}=(1992\pm 12(\mathrm{stat}){}_{-6}^{+15}(\mathrm{sys}))\mathrm{MeV}/c^2$, and width $\mathrm{\Gamma }=(132\pm 22(\mathrm{stat}){}_{-4}^{+17}(\mathrm{sys}))\mathrm{MeV}$. These measurements provide important input for the strangeonium spectrum. In addition, the $f_0(980)-a_0(980{)}^0$ mixing signal in $J/\psi \to \varphi f_0(980)\to \varphi a_0(980{)}^0$ and the corresponding electromagnetic decay $J/\psi \to \varphi a_0(980{)}^0$ are measured with improved precision, providing crucial information to understand the nature of $a_0(980{)}^0$ and $f_0(980)$.

We revisit the concept of phase time, which has been previously proposed as a solution to the problem of time in quantum gravity. Concretely, we show how the geometry of configuration space together with the phase of the wave function of the Universe can, under certain conditions, lead to the definition of a positive-definite squared norm from which probabilities can be defined. The norm is conserved under time evolution, and we obtain a version of Ehrenfest’s theorem that is analogous to the one in ordinary quantum mechanics. We address how the present approach avoids some difficulties that were encountered in previous attempts at defining an Ehrenfest theorem relative to phase time in the context of relativistic quantum mechanics and canonical quantum gravity, and how it is connected to a notion of gauge fixing the inner product. We conclude with a brief outlook.

We consider a conformally coupled scalar quantum field theory (QFT) on ($2+1$)-dimensional static Einstein universe $R\times S^2$ and write down the free theory Hilbert space. We explain that this theory is secretly a QFT in ($2+1$)-dimensional de Sitter space because all the quantum observables experience “quantum revivals,” which naturally restricts the timelike $R$ to the appropriate de Sitter time range. Our construction circumvents the causal obstruction to formulating QFT in de Sitter due to event horizons. There are not any in static Einstein. The “unitary gauge” description of the theory is realized by the zonal harmonics $P_{\ell }(\widehat{n}·{\widehat{n}}^{\prime })$. We verify that interactions with conformally invariant external sources are mediated only by these modes. Hence these modes comprise the complete basis of the “bulk” theory. When the theory is cut off in the UV, the basis dimension scales as the Bekenstein-Hawking formula.

In this work, we undertake an analysis of new wormhole solutions within an action-dependent Lagrangian framework. These geometries can be traversable and supported by a positive energy density. The modification of the gravitational field equations is produced by the inclusion in the gravitational Lagrangian linear of a background four-vector ${\lambda }_{\mu }$. This new term expands significantly the conventional description of gravity making it highly nonlinear, and therefore drawing general conclusions about legitimate forms of ${\lambda }_{\mu }$ proves a formidable task in general. It is, then, customary to adopt an ansatz that strikes a balance between enabling new phenomenology while retaining a significant degree of generality on ${\lambda }_{\mu }$. Ours is given by the choice ${\lambda }_{\mu }=(0,{\lambda }_1(r),0,0)$, with an arbitrary ${\lambda }_1(r)$. By setting ${\lambda }_1(r)=-1/r$ we craft new families with physically desirable properties, but the wormholes thus generated turn out to be conical, as evidenced by an angle deficit, in a similar fashion to other known solution families. Under the general shape of ${\lambda }_1(r)$, we demonstrate that these solutions are not compatible with the null energy condition in general, as it happens to their general relativity counterparts, except on specific occasions where the derivative of the redshift function of the metric diverges at the throat (however, in these latter cases, the traversability of the wormhole will be disrupted). On the other hand, it is possible to solve the conical character and satisfies the flatness condition for more general functions of ${\lambda }_1(r)$.

It has been conjectured that quantum gravity effects may cause the black-to-white hole transition due to quantum tunneling. The transition amplitude of this process is explored within the framework of the spin foam model on a 2-complex containing 56 vertices. We develop a systematic way to construct the bulk triangulation from the boundary triangulation to obtain the 2-complex. By using Thiemann’s complexifier coherent state as the boundary state to resemble the semiclassical geometry, we introduce a procedure to calculate the parameters labeling the coherent state from the continuous curved geometry. Considering that triad fields of different orientations, i.e., $e_i^a$ and $-e_i^a$, give the same intrinsic geometry of the boundary, we creatively adopt the boundary state as a superposition of the coherent states associated with both orientations. We employ the method of complex critical point to numerically compute the transition amplitude. Despite the numerical results, it is interesting to note that the transition amplitude is dominated by the terms allowing the change in orientation. This suggests that the black-to-white hole transition should be accompanied by the quantum tunneling process of a change in orientation.

We study the electromagnetic radiation reaction on a charged particle around a weakly magnetized Kerr black hole by numerically solving the Teukolsky equation to find the energy fluxes in electromagnetic radiation at the horizon and at spatial infinity. We also employ analytical methods in the low-frequency limit, finding excellent agreement with the numerical results. For a wide range of parameters, the energy fluxes on the horizon are negative for all orbital radii: the modes are amplified through superradiance. More interestingly, the flux on the horizon is larger (in absolute value) than the flux at infinity for orbits with orbital radius $r_0\gtrsim 9M$—“floating orbits” are a generic outcome of having magnetic fields around black holes. Particles on these orbits extract energy from the black hole through their radiation field; the net effect is an increase in the particles’ kinetic energy so that they outspiral to infinity. Although in realistic accretion disks viscous forces are expected to dominate, floating orbits remain an interesting feature of the existence of ergoregions in black hole spacetimes.

We present the algebraic classification of the gravitational field in four-dimensional general metric-affine geometries, thus extending the current results of the literature in the particular framework of Weyl-Cartan geometry by the presence of the traceless nonmetricity tensor. This quantity switches on four of the eleven fundamental parts of the irreducible representation of the curvature tensor under the pseudo-orthogonal group, in such a way that three of them present similar algebraic types as the ones obtained in Weyl-Cartan geometry, whereas the remaining one includes thirty independent components and gives rise to a new algebraic classification. The latter is derived by means of its principal null directions and their levels of alignment, obtaining a total number of sixteen main algebraic types, which can be split into many subtypes. As an immediate application, we determine the algebraic types of the broadest family of static and spherically symmetric black hole solutions with spin, dilation, and shear charges in metric-affine gravity.

We use a combination of high-redshift observables to extract the strongest constraints to date on the fraction of axion fuzzy dark matter (FDM) in the mass window ${10}^{-26}\mathrm{eV}\lesssim m_{\mathrm{FDM}}\lesssim {10}^{-23}\mathrm{eV}$. These observables include ultraviolet luminosity functions at redshifts 4–10 measured by the Hubble Space Telescope, a constraint on the neutral hydrogen fraction from high-redshift quasar spectroscopy, the cosmic microwave background optical depth to reionization measurement from Planck, and upper bounds on the 21 cm power spectrum from HERA. In order to calculate these signals for FDM cosmology, we use the 21 cmfirstclass code to interface between axiclass and 21 cmfast and consistently account for the full cosmic history from recombination to reionization. To facilitate a full Bayesian likelihood analysis, we developed a machine-learning-based pipeline, which is both accurate and enables a swift statistical inference, orders of magnitude faster than a brute-force approach. We find that FDM of mass $m_{\mathrm{FDM}}={10}^{-23}\mathrm{eV}$ is bound to less than 16% of the total dark matter, where the constrains strengthen toward smaller masses, reaching down to 1% for $m_{\mathrm{FDM}}={10}^{-26}\mathrm{eV}$, both at 95% confidence level. In addition, we forecast that a future detection of the 21 cm power spectrum with HERA will lower the upper bound at $m_{\mathrm{FDM}}={10}^{-23}\mathrm{eV}$ to $\lesssim 1\%$.

Cosmological correlators capture the spatial fluctuations imprinted during the earliest episodes of the Universe. While they are generally very nontrivial functions of the kinematic variables, they are known to arise as solutions to special sets of differential equations. In this work we use this fact to uncover the underlying tame structure for such correlators and argue that they admit a well-defined notion of complexity. In particular, building upon the recently proposed kinematic flow algorithm, we show that tree-level cosmological correlators of a generic scalar field theory in a Friedmann-Lemaître-Robertson-Walker spacetime belong to the class of Pfaffian functions. Since Pfaffian functions admit a notion of complexity, we can give explicit bounds on the topological and computational complexity of cosmological correlators. We conclude with some speculative comments on the general tame structures capturing all cosmological correlators and the connection between complexity and the emergence of time.

We investigate the properties of quark matter and quark stars (QSs) within the SU(3) Nambu-Jona-Lasinio model, considering the effects of axion fields and vector interactions. Under the assumption of the absolutely stable condition of strange quark matter, we find that including axion effects and vector interactions significantly influences the equation of state, constituent quark mass, isospin asymmetry for $u$ and $d$ quarks, quark fractions, sound velocity, and the maximum mass of QSs. In particular, our results indicate that the central baryon density of the maximum star mass and the polytropic index $\gamma$ both decrease with increasing star mass, and we can describe the recently observed extremely large pulsars as QSs using absolutely stable strange quark matter.

The recent AMS-02 measurements of cosmic-ray (CR) deuteron flux suggest the presence of primary deuterons in quantities far exceeding predictions from big bang nucleosynthesis. This poses a significant challenge to modern astrophysics, as no known processes can account for such large amounts of deuterons without violating existing constraints [R. I. Epstein et al., Nature (London) 263, 198 (1976)]. In contrast, it has recently been proposed that the AMS-02 measurements can be explained by a purely secondary origin when contributions from heavier nuclei are considered. In this study, we recalculate the secondary deuteron flux using production cross sections updated with the latest data. We find that the deuteron production cross sections are overestimated in the commonly used calculation tools for CR propagation, and a primary deuteron component is still necessary. We then propose a novel process for generating primary deuterons at CR sources through a fusion mechanism, which is naturally unique to deuterons. This model could explain the observed deuteron excess while maintaining consistency with other CR measurements.

Next-generation gravitational-wave detectors like the Einstein Telescope and Cosmic Explorer, currently in their preparatory phase, have the potential to significantly improve our understanding of astrophysics, cosmology, and fundamental physics. We examine how the arm orientations of the proposed detectors influence the sensitivity of a combined Einstein Telescope–Cosmic Explorer network with respect to the sensitivity to the stochastic gravitational-wave background and compact binary coalescences, where measuring both gravitational-wave polarizations is favorable. We present a method to optimize the arm orientations in the network for these two targets, and also demonstrate how to achieve a balanced configuration for both stochastic background and compact binary coalescence searches. For five specific network configurations, we explicitly compare the sensitivity to the stochastic background and binary neutron star mergers. For the latter, we conduct Bayesian parameter estimation on the extrinsic parameters of a reference binary neutron star system to assess sky localization and distance estimation capabilities. These are illustrated through efficiency curves showing the fraction of events meeting sky localization and distance uncertainty criteria as a function of redshift. Our findings suggest that globally coordinating efforts towards the next-generation gravitational-wave detector network is advantageous.

We consider resurgence for the nonconformal Bjorken flow with Fermi-Dirac and Bose-Einstein statistics in the extended relaxation-time approximation. First, we examine the full formal transseries expanded around the equilibrium and then construct the resurgent relation by looking at the structure of Borel-transformed ordinary differential equations. We form a conjecture of the resurgent relation based on the consideration that the Stokes constants constituting the resurgent relation originate only from singularities of dissipative variables on the Borel plane and that the other variables such as temperature and chemical potential become Borel nonsummable through nonlinear terms with the dissipative variables. We numerically check the conjecture for fundamental variables by explicitly evaluating the values of the dominant Stokes constant depending on the initial conditions and the particle mass. We also comment on some issues related to transseries structure and resurgence, such as the case of broken U(1) symmetry, the massless case, generalized relaxation time, and attractor solutions.

We investigate the potential of a minimal scotogenic model with two additional scalar doublets and a single heavy Majorana fermion to explain neutrino masses, dark matter, and the baryon asymmetry of the Universe. In this minimal setup, leptogenesis is purely flavored, and a second Majorana neutrino is not necessary because the Yukawa couplings of the extra doublets yield the necessary $CP$-odd phases. The mechanism we employ can also be applied to a wide range of scenarios with at least one singlet and two gauge multiplets. Despite stringent limits from the dark matter abundance, direct detection experiments, and the baryon asymmetry of the Universe, we find a parametric region consistent with all bounds which could resolve the above shortcomings of the Standard Model of particle physics. Methodically, we improve on the calculation of correlations between the mixing scalar fields given their finite width. We also present an argument to justify the kinetic equilibrium approximation for out-of-equilibrium distribution functions often used in calculations of baryogenesis and leptogenesis.

In this article, we investigate the $Y=0$ $SU(2)$ scalar triplet and $Z_2$-odd scalar singlet extension of the standard model (SM). Here, the triplet charged Higgs boson decays to $Z{W}^{\pm }$, breaking the custodial symmetry at the tree level, proportional to the triplet vacuum expectation value, while the singlet provides the dark matter (DM) relic. The triplet neutral Higgs boson ($T^0$) can decay fully invisibly owing to the triplet-singlet portal coupling ${\lambda }_{st}$. The other SM Higgs portal couplings ${\lambda }_{ht},{\lambda }_{hs}$ are constrained by the Higgs boson to diphoton observations, and the dark matter relic and direct searches as well as invisible Higgs decay bounds, respectively. For a cleaner signature, we indulge in a futuristic multi-TeV muon collider (MuC) to probe both the triplet scalars ($T^{\pm },T^0$) via vector boson fusion with forward muon tagging, at the center-of-mass energies of 3 and 10 TeV. The analysis is comprised of a traditional cut-based approach and a boosted decision tree (BDT) classifier, where the latter is more effective for lower energies. With large missing energy contributions to the final states from combinations of DM mass and ${\lambda }_{st}$, the 3 TeV MuC is projected to probe triplet scalar masses of 450 GeV with the BDT classifier. The 10 TeV MuC can pinpoint the custodial symmetry breaking $T^{\pm }\to Z{W}^{\pm }\to 3$-lepton decay up to 800 GeV of triplet scalar mass from cut-based analysis, with ${\lambda }_{st}$ as low as 1.5 being adequate.