A hidden sector that kinetically mixes with the minimal supersymmetric standard model provides simple and well-motivated dark matter candidates that possess many of the properties of a traditional weakly interacting massive particle (WIMP). These supersymmetric constructions can also provide a natural explanation for why the dark matter is at the weak scale even if it resides in a hidden sector. In the hidden sector, a natural pattern of symmetry breaking generally makes particles and their superpartners lie around the same mass scale, opening novel possibilities for a variety of cosmological histories and complex indirect detection signatures.

We study the most recently observed excited $B_c$ states with the Dyson-Schwinger equation and the Bethe-Salpeter equation approach of continuum QCD. The obtained $M_{B_c^{+}(2S)}=6.813(16)\mathrm{GeV}$, $M_{B_c^{*+}(2S)}=6.841(18)\mathrm{GeV}$ and the mass splitting $M_{B_c^{+}(2S)}-M_{B_c^{*+}(2S)}^{\mathrm{rec}}\approx 0.039\mathrm{GeV}$ agree with the observations very well. Moreover we predict the leptonic decay constant $f_{B_c^{+}(2S)}=-0.165(10)\mathrm{GeV}$, $f_{B_c^{*+}(2S)}=-0.161(7)\mathrm{GeV}$, respectively.

The hadronic weak decays of ${\mathrm{\Lambda }}_c$ are studied in the framework of a constituent quark model. With the combined analysis of the Cabbibo-favored processes, ${\mathrm{\Lambda }}_c\to \mathrm{\Lambda }{\pi }^{+}$, ${\mathrm{\Sigma }}^0{\pi }^{+}$, and ${\mathrm{\Sigma }}^{+}{\pi }^0$, we confirm that the nonfactorizable transition mechanisms play a crucial role in the understanding of their compatible branching ratios. We emphasize that the SU(3) flavor symmetry breaking effects, which is generally at the order of 1–2%, can be amplified by the destructive interferences among the pole terms in the diagrams with internal conversion. Some contributions are sensitive to the spatial distribution of the scalar-isoscalar light-quark sector in the ${\mathrm{\Lambda }}_c$, and its overlap with the light quarks in the final state hyperon. Namely, a compact diquark configuration is disfavored.

We suggest a few particle physics processes in which excited $2p$ pionium ${\mathrm{A}}_{2\pi }^{\prime }$ may be observed. They include the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ annihilation, the $V^0\to {\pi }^0{\ell }^{+}{\ell }^{-}$ and $K^{\pm }\to {\pi }^{\pm }{\ell }^{+}{\ell }^{-}$ ($\ell =e$, $\mu$) decays, and the photoproduction of two neutral pions from nucleons. We analyze available experimental data and find that they, in some cases, indicate the presence of $2p$ pionium, but do not provide definite proof.

We derive an effective dual holographic Einstein-Maxwell theory, applying renormalization group transformations to interacting Dirac fermions in a recursive way. In particular, we show how both background metric tensor and U(1) gauge fields become dynamical to describe the renormalization group flows of coupling functions and order-parameter fields of the corresponding quantum field theory through natural emergence of an extra-dimensional space, respectively. Finally, we propose a prescription on how to calculate correlation functions in a nonperturbative way, where quantum fluctuations of both metric and gauge fields are frozen to cause a classical field theory of the Einstein-Maxwell type in the large $N$ limit. Here, $N$ is the flavor degeneracy of Dirac fermions. This prescription turns out to coincide with that of the holographic duality conjecture.

We initiate the study of applications of machine learning to Seiberg duality, focusing on the case of quiver gauge theories, a problem also of interest in mathematics in the context of cluster algebras. Within the general theme of Seiberg duality, we define and explore a variety of interesting questions, broadly divided into the binary determination of whether a pair of theories picked from a series of duality classes are dual to each other, as well as the multiclass determination of the duality class to which a given theory belongs. We study how the performance of machine learning depends on several variables, including number of classes and mutation type (finite or infinite). In addition, we evaluate the relative advantages of Naive Bayes classifiers versus convolutional neural networks. Finally, we also investigate how the results are affected by the inclusion of additional data, such as ranks of gauge/flavor groups and certain variables motivated by the existence of underlying Diophantine equations. In all questions considered, high accuracy and confidence can be achieved.

Within the next several years, pulsar-timing array programs will likely usher in the next era of gravitational-wave astronomy through the detection of a stochastic background of nanohertz-frequency gravitational waves, originating from a cosmological population of inspiraling supermassive binary black holes. While the source positions will likely be isotropic to a good approximation, the gravitational-wave angular power distribution will be anisotropic, with the most massive and/or nearby binaries producing signals that may resound above the background. We study such a realistic angular power distribution, developing fast and accurate sky-mapping strategies to localize pixels and extended regions of excess power while simultaneously modeling the background signal from the less massive and more distant ensemble. We find that power anisotropy will be challenging to discriminate from isotropy for realistic gravitational-wave skies, requiring SNR $>10$ in order to favor anisotropy with $10:1$ posterior odds in our case study. Amongst our techniques, modeling the population signal with multiple point sources in addition to an isotropic background provides the most physically motivated and easily interpreted maps, while spherical-harmonic modeling of the square-root power distribution, $P(\widehat{\mathrm{\Omega }}{)}^{1/2}$, performs best in discriminating from overall isotropy. Our techniques are modular and easily incorporated into existing pulsar-timing array analysis pipelines.

In this work, new solutions for regular black holes that have multihorizons are proposed. These are formed by the direct product of solutions already published in the literature, which are described through the coupling of gravity with nonlinear electrodynamics. We analyze the regularity of the spacetime, the electric field, and the energy conditions of each solution. The strong energy condition is always violated within the event horizon in all solutions, while other energy conditions depend on the ratio between extreme charges of isolated solutions. For solutions with four horizons, we present two examples, Bardeen-Culetu and Balart-Culetu. Both solutions are regular, but the first do not satisfy all the energy conditions, except the strong, because it has an extreme charge ratio of 1.57581, great value. The second solution, on the other hand, can satisfy all other energy conditions, except the SEC, and has an extreme charge ratio of 1.09915, a value that allows this feature. A regular solution with up to six horizons is proposed, Balart-Culetu-Dymnikova, where, for a given charge value, we can verify that it satisfies all energy conditions, except the strong one. This was possible due to the ratio between extreme charges that are neither too high nor too close. We propose solutions with any number of horizons. We show that points where $-F(r)$ has a non-null minimum represent a cusp in the Lagrangian $-L(F)$. We also show an example of multihorizon solution with magnetic charge. Multihorizon solutions may exhibit exotic properties, such as negative energy density, or violation of energy conditions, but which can be circumvented with a selected choice of customized solutions and extreme charge values, resulting in regular black hole solutions that satisfy all energy conditions, less the strong.

We study the stability of relativistic stars in scalar-tensor theories with a nonminimal coupling of the form $F(\varphi )R$, where $F$ depends on a scalar field $\varphi$ and $R$ is the Ricci scalar. On a spherically symmetric and static background, we incorporate a perfect fluid minimally coupled to gravity as a form of the Schutz-Sorkin action. The odd-parity perturbation for the multipoles $l\ge 2$ is ghost-free under the condition $F(\varphi )>0$, with the speed of gravity equivalent to that of light. For even-parity perturbations with $l\ge 2$, there are three propagating degrees of freedom arising from the perfect-fluid, scalar-field, and gravity sectors. For $l=0$, 1, the dynamical degrees of freedom reduce to two modes. We derive no-ghost conditions and the propagation speeds of these perturbations and apply them to concrete theories of hairy relativistic stars with $F(\varphi )>0$. As long as the perfect fluid satisfies a weak energy condition with a positive propagation speed squared $c_m^2$, there are neither ghost nor Laplacian instabilities for theories of spontaneous scalarization and Brans-Dicke (BD) theories with a BD parameter ${\omega }_{\mathrm{BD}}>-3/2$ (including $f(R)$ gravity). In these theories, provided $0<c_m^2\le 1$, we show that all the propagation speeds of even-parity perturbations are subluminal inside the star, while the speeds of gravity outside the star are equivalent to that of light.

Since the current evidence of the existence of dark matter is revealed only through its gravitational influence, the way it couples to gravity must be then of primary importance. Here, unlike the standard model sector, which is typically coupled to a metric, dark matter is supposed to couple to a spacetime affine connection only through a $Z_2$-symmetry breaking term. We show that this structure leads to a coupling between dark matter, which is considered scalar, and the standard model Higgs potential. This induces dark matter decays into standard model particles through the Higgs boson, which acts as a portal between the visible and the dark sectors. We study thoroughly the resulting decay modes for various mass ranges and provide relevant bounds on the nonminimal coupling to affine gravity in line with observational data. Moreover, we find that the coupling to a Higgs boson can be sufficiently large to facilitate the production of dark matter lighter than 10 GeV at current and future high energy colliders.

The nonlinear, or null gravitational, memory effect for zoom-whirl orbits around fast spinning Kerr black holes for extreme mass ratio systems has a staircase structure. The latter is characterized by a periodic fast increase in the memory during the whirl phases of the orbit and near constant levels when the orbit is near apoapsis. We study the contribution of different spherical harmonic modes to this effect and discuss the relative importance, thereof. Because the hereditary memory effect increases in magnitude linearly in the number of periapsis passages on a dynamical time scale, while the oscillatory parent gravitational waves are sourced by an orbit that evolves on a much longer radiation reaction time scale, the magnitude of the former relative to the latter increases with time. We also consider orphan memory and the memory effect for extreme mass ratio inspirals. We then discuss the prospect of detection with the Laser Interferometer Space Antenna.

The data from the ground-based interferometric gravitational-wave (GW) detectors is often plagued by highly localized short-duration glitches which pose a serious challenge for any transient GW search. These glitches are not of any astrophysical origin but rather arise due to environmental or instrumental artifacts. In this work, we propose a glitch identification algorithm for the scenario of presence of a glitch, occurring within 20 s before or 10 s after the merger time of a coalescing compact binary system with chirp mass less than or equal to $5M_{\odot }$. We devise the chirp mass consistency parameter across different Q-planes in the Q-transform. We test this algorithm using a variety of short-duration glitches from the first and second observational runs of Advanced LIGO and Virgo detectors in the simulations with long-duration binary inspiral signal. The demonstration of this glitch identification algorithm in the simulated signals of generic low mass and low eccentricity binary systems shows the direct application of it in the long-duration unmodeled searches.

In this paper we test the weak cosmic censorship conjecture (WCCC) in the nearly extremal static charged black holes of Lanczos-Lovelock-Maxwell gravity based on the new version of gedanken experiments proposed by Sorce and Wald. After introducing the null energy condition of the matter fields, we show that the (nearly) extremal black holes can be destroyed under the first-order approximation for the case with $S^{\prime }(r_h)\le 0$, where $S(r_h)$ is the entropy of the background black hole geometry in Lanczos-Lovelock gravity. It implies that the WCCC is violated in these situations. For the case with $S^{\prime }(r_h)>0$, the nearly extremal black holes cannot be overcharged by the new version of the gedanken experiments for both first- and second-order approximations of perturbation. These results indicate that the WCCC is satisfied in Lanczos-Lovelock gravity with the condition $S^{\prime }(r_h)>0$. Our work also implies that the WCCC will play a natural role to constrain Lanczos-Lovelock gravities. Finally, we also show that the condition $S^{\prime }(r_h)<0$ to destroy the black holes implies that the nearly extremal black hole is thermodynamically unstable under the first-order approximation.

We construct hairy black hole solutions in a particular set of tensor-multiscalar theories of gravity for which the target-space admits a Killing vector field with periodic flow that is furthermore the generator of a one-parameter family of point transformations which leave the whole theory invariant. As for black holes with scalar hair in general relativity, these must be rotating objects as the scalarization arises from superradiant instability. We analyze the most fundamental rotating solutions (winding number $m=1$) in five theories which differ from each other by the value of the Gauss curvature of the target-space. We investigate the domain of existence of these solutions, i.e., how they depart from Kerr black holes or solitons, and verify that there is a nonuniqueness region where for a fixed pair of mass and angular momentum, different black holes can be found. Based on the ration between the mass stored in the scalar hair and the horizon mass we access how hairy these solutions are and show that with increasing Gauss curvature, hairier solutions are found. Interestingly, the smaller this curvature is, the higher is the minimum ratio $J/M^2$ featured by the solution set. The horizon area is calculated and in the nonuniqueness domain some (but not all) hairy black holes are more thermodynamically stable than bald Kerr black holes. Finally, we analyze how bulgy the horizon of these hairy black holes are through the ratio between the equatorial and polar circumferences and we observe that for none of these solutions it overcomes the deformation of extremal Kerr black holes.

In this paper we analyze the Bianchi IX Universe dynamics within the corner region associated to the potential term which the spatial curvature induces in the minisuperspace. We investigate the dynamics in terms of the WKB scenario: the isotropic Misner variable ($\alpha$) and one of the two anisotropic variables (${\beta }_{+}$) are treated as semiclassical, while the remaining anisotropy (${\beta }_{-}$) is described on a pure quantum level. The quantum dynamics always reduces to the one of a time-dependent Schrödinger equation for a harmonic potential with a time dependent frequency. The study is done in the vacuum and in the presence of a massless scalar field $\varphi$ and a cosmological constant term $\mathrm{\Lambda }$. The vacuum case is treated in the limits of a collapsing and an expanding Universe, while the dynamics in presence of $\varphi$ and $\mathrm{\Lambda }$ is studied only for $t\to \infty$. In both analyses the quantum dynamics of the anisotropy variable ${\beta }_{-}$ suggests a suppression of the quantum anisotropy associated. In the vacuum case the corner configuration becomes an attractor for the dynamics and the evolution resembles that of a Taub cosmology in the limit of a nonsingular initial Universe. This suggests that if the Bianchi dynamics enters deeply enough in the potential corner the initial singularity is removed and a Taub picture emerges. The case when $\varphi$ is present well mimics the de Sitter phase of an inflationary Universe. Here we show that both the classical and quantum anisotropies are exponentially suppressed and therefore the resulting dynamics corresponds to an isotropic closed Robertson-Walker geometry.

The multitude of binary black hole coalescence detections in gravitational waves has renewed our interest on environments that can be the cradle of these mergers. In this work we study merger rates of binary black holes in globular clusters that are among the most dense stellar environments and a natural place for the creation of black hole binaries. To model these systems with all their variations we rely on the observational properties of the known Milky Way globular clusters. We consider direct capture events between black holes, as well as soft interactions of black hole binaries with stars as third bodies that accelerate the evolution of these binaries. We find that binary black holes from direct captures merge at an averaged rate of $0.3-5\times {10}^{-11}{\mathrm{yr}}^{-1}$ per cluster. Third body soft interactions are a much more prominent channel, giving an averaged rate of $2-4\times {10}^{-10}{\mathrm{yr}}^{-1}$ per cluster. Those rates in globular clusters can lead to a cumulative merger rate of about 100 mergers per year up to a redshift of 1, i.e., a significant fraction of the detectable in the near future binary black hole coalescence events. Further observations of cluster properties both in terms of their masses, profile properties, velocity dispersion of stars, and their cosmological distribution, will allow us to better constrain the contribution of these environments to the detectable coalescence events rate.

A new family of nonrelativistic, Newtonian, nonquantum equilibrium configurations describing galactic halos is introduced, by considering strange quark matter conglomerates with masses larger than about 8 GeV as new possible components of the dark matter. Originally introduced to explain the state of matter in neutron stars, such conglomerates may also form in the high density and temperature conditions of the primordial Universe and then decouple from ordinary baryonic matter, providing the fundamental components of dark matter for the formation of pristine gravitational potential wells and the subsequent evolution of cosmic structures. The obtained results for halo mass and radius are consistent with the rotational velocity curve observed in the Galaxy. Additionally, the average density of such dark matter halos is similar to that derived for halos of dwarf spheroidal galaxies, which can therefore be interpreted as downscaled versions of larger dark matter distributions around Milky-Way-sized galaxies and hint for a common origin of the two families of cosmic structures.

The perturbative QCD static potential and ultrasoft contributions, which together give the static energy, have been calculated to three- and four-loop order respectively, by several authors. Using the renormalization group, and Padé approximants, we estimate the four-loop corrections to the static energy. We also employ the optimal renormalization method and resum the logarithms of the perturbative series in order to reduce sensitivity to the renormalization scale in momentum space. This is the first application of the method to results at these orders. The convergence behavior of the perturbative series is also improved in position space using the restricted Fourier transform scheme. Using optimal renormalization, we have extracted the value of ${\mathrm{\Lambda }}_{\mathrm{QCD}}^{\overline{\mathrm{MS}}}$ at different scales for two active flavors by matching to the static energy from lattice QCD simulations.

The electrical and Hall conductivities in a uniform magnetic field are evaluated for an interacting pion gas using the kinetic theory approach within the ambit of relaxation time approximation. The in-medium cross sections vis-à-vis the relaxation time for $\pi \pi$ scattering are obtained using a one-loop modified thermal propagator for the exchanged $\rho$ and $\sigma$ mesons using thermal field theoretic techniques. For higher values of the magnetic field, a monotonic increase of the electrical conductivity with the temperature is observed. However, for a given temperature, the conductivity is found to decrease steadily with magnetic field. The Hall conductivity, at lower values of the magnetic field, is found to decrease with the temperature more rapidly than the electrical conductivity, whereas at higher values of the magnetic field, a linear increase is seen. Use of the in-medium scattering cross section is found to produce a significant effect on the temperature dependence of both electrical and Hall conductivities compared to the case where the vacuum cross section is used.

In a recent letter we proposed a new nonthermal mechanism of dark matter production based on vacuum misalignment, where both the Higgs boson and a very light pseudoscalar $\eta$ emerge from the dark sector. In this paper, we identify the parameter space in a composite scenario where the light pseudoscalar can be produced in the sun and explain the XENON1T excess in electron recoil data. The model’s dark matter candidate has a mass around 50 TeV and out of range for direct detection. Testable predictions include gravitational waves at frequencies in the Hz range from a cosmological phase transition, an exotic decay $Z\to \gamma +\mathrm{inv}$ with rates $4÷16\times {10}^{-12}$ testable at a future Tera-Z collider, and an enhancement by $17÷40\%$ of the branching ratio $K_L\to {\pi }^0+\mathrm{inv}$, not enough to explain the KOTO anomaly. All these predictions may be confirmed by future experiments.