We model clusters of axions with spherically symmetric spatial but arbitrary momentum distributions and study the directional profile of photos produced in their evolution through spontaneous and stimulated decay of axions via the process $a\to \gamma \gamma$. Several specific examples are presented.

The aim of this article is to explore a potential usability of a photon-photon self-interaction from the noncommutative quantum electrodynamics (NCQED) in the case of light-by-light scattering ($\gamma \gamma \to \gamma \gamma$) in ultraperipheral $\mathrm{Pb}+\mathrm{Pb}$ collisions, a reaction measured recently by ATLAS and planned for future experiments in hadron-hadron colliders. We compute the total cross section from both, the full one-loop standard model (SM) and the tree-level NCQED amplitudes, in the equivalent photon approximation with impact parameters, for various noncommutative scales, ${\mathrm{\Lambda }}_{\mathrm{NC}}$, and incoming nuclear spin-energy combinations. We find that NCQED contribution to the cross section has considerable increase at diphoton invariant mass range higher than ${\mathrm{\Lambda }}_{\mathrm{NC}}$, while the SM contribution is strongly suppressed in such region. Our results show that the current ATLAS $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}=5.02\mathrm{TeV}$ experiment can only probe ${\mathrm{\Lambda }}_{\mathrm{NC}}<100\mathrm{GeV}$ region. On the other hand, future hadron-hadron collider proposals could have the potential to extend to ${\mathrm{\Lambda }}_{\mathrm{NC}}\lesssim 300\mathrm{GeV}$ region, making the performance of $\mathrm{Pb}\mathrm{Pb}\to \mathrm{Pb}\mathrm{Pb}\gamma \gamma$ scattering on testing space-time noncommutativity close to that of the previously proposed photon-photon mode of linear electron-positron collider.

We construct chiral theories with the smallest number $n_{\chi }$ of Weyl fermions that form an anomaly-free set under various Abelian gauge groups. For the $U(1)$ group, where $n_{\chi }=5$, we show that the general solution to the anomaly equations is a set of charges given by cubic polynomials in three integer parameters. For the $U(1)\times U(1)$ gauge group we find $n_{\chi }=6$, and derive the general solution to the anomaly equations, in terms of 6 parameters. For $U(1)\times U(1)\times U(1)$ we show that $n_{\chi }=8$, and present some families of solutions. These chiral gauge theories have potential applications to dark matter models, right-handed neutrino interactions, and other extensions of the Standard Model. As an example, we present a simple dark sector with a natural mass hierarchy between three dark matter components.

We explore the thermodynamics of the $1+1$-dimensional Gross-Neveu (GN) model at a finite number of fermion flavors $N_{\mathrm{f}}$, finite temperature, and finite chemical potential using lattice field theory. In the limit $N_{\mathrm{f}}\to \infty$ the model has been solved analytically in the continuum. In this limit three phases exist: a massive phase, in which a homogeneous chiral condensate breaks chiral symmetry spontaneously; a massless symmetric phase with vanishing condensate; and most interestingly an inhomogeneous phase with a condensate, which oscillates in the spatial direction. In the present work we use chiral lattice fermions (naive fermions and SLAC fermions) to simulate the GN model with 2, 8, and 16 flavors. The results obtained with both discretizations are in agreement. Similarly as for $N_{\mathrm{f}}\to \infty$ we find three distinct regimes in the phase diagram, characterized by a qualitatively different behavior of the two-point function of the condensate field. For $N_{\mathrm{f}}=8$ we map out the phase diagram in detail and obtain an inhomogeneous region smaller as in the limit $N_{\mathrm{f}}\to \infty$, where quantum fluctuations are suppressed. We also comment on the existence or absence of Goldstone bosons related to the breaking of translation invariance in $1+1$ dimensions.

Two-body hadronic weak decays of the charmed baryon ${\mathrm{\Omega }}_c$, including the Cabibbo-favored (CF), singly Cabibbo-suppressed (SCS), and doubly Cabibbo-suppressed (DCS) modes, are studied systematically in this work. To estimate nonfactorizable contributions, we work in the pole model for the $P$-wave amplitudes and current algebra for the $S$-wave amplitudes. Among all the channels decaying into a baryon octet and a pseudoscalar meson, ${\mathrm{\Omega }}_c\to {\mathrm{\Xi }}^0{\overline{K}}^0$ is the only allowed CF mode. The predicted branching fraction of order 3.8% and large and positive decay asymmetry of order 0.50 indicate that a measurement of this mode in the near future is promising. Proceeding through purely nonfactorizable contributions, the SCS mode ${\mathrm{\Omega }}_c\to {\mathrm{\Lambda }}^0{\overline{K}}^0$ and DCS mode ${\mathrm{\Omega }}_c\to {\mathrm{\Lambda }}^0\eta$ are predicted to have branching fractions as large as 0.8% and 0.4%, respectively. The two DCS modes ${\mathrm{\Omega }}_c\to {\mathrm{\Sigma }}^0\eta$ and ${\mathrm{\Omega }}_c\to {\mathrm{\Lambda }}^0{\pi }^0$ are suggested to serve as new physics searching channels for their vanishing SM background.

In the framework of QCD sum rules, we investigate the $q{q}^{\prime }\overline{Q}\overline{Q}$ tetraquark structure with quantum number $J^P=1^{+}$, which is embedded in two types of configurations, the $[8_c{]}_{q\overline{Q}}\otimes [8_c{]}_{q^{\prime }\overline{Q}}$ and $[1_c{]}_{q\overline{Q}}\otimes [1_c{]}_{q^{\prime }\overline{Q}}$ with $Q=b$, $c$, $q=u$, and $q^{\prime }=d$, $s$. Our finding confirms the lattice QCD result that the bottom tetraquark states could exist and their masses are evaluated. In the calculation, the nonperturbative condensate contributions up to dimension eight in operator product expansion are considered, and those terms linear to the strange quark mass $m_s$ are kept. It is found that for octet-octet configuration the masses of potential tetraquark states are about 11.28 GeV for the $ud\overline{b}\overline{b}$ system, and 11.36 and 11.39 GeV for the $us\overline{b}\overline{b}$ system, which are above the corresponding two-meson thresholds. For molecular configuration, the corresponding masses are found below the thresholds, that is, 10.36 GeV and 10.51 GeV, respectively. The possible tetraquark decay channels are analyzed and the strong decay rates are evaluated. The mass dependence on the radiative correction and the condensates is estimated. Moreover, the doubly charmed tetraquark states are also considered.

At a nonzero temperature $T$, a constant field ${\overline{A}}_0\sim T/g$ generates nontrivial eigenvalues of the thermal Wilson line. We discuss contributions to the free energy of such a holonomous plasma when the coupling constant, $g$, is weak. We review the computation to $\sim g^2$ by several alternate methods, and show that gauge invariant sources, which are nonlinear in the gauge potential $A_0$, generate novel contributions to the gluon self-energy at $\sim g^2$. These ensure the gluon self-energy remains transverse to $\sim g^2$, and are essential in computing contributions to the free energy at $\sim g^3$ for small holonomy, ${\overline{A}}_0\sim T$. We show that the contribution $\sim g^3$ from off-diagonal gluons is discontinuous as the holonomy vanishes. The contribution from diagonal gluons is continuous as the holonomy vanishes, but sharply constrains the possible sources which generate nonzero holonomy, and must involve an infinite number of Polyakov loops.

Pion beta decay, ${\pi }^{+}\to {\pi }^0{e}^{+}\nu (\gamma )$, provides a theoretically clean $\pm 0.3\%$ determination of the Cabibbo-Kobayashi-Maskawa matrix element $V_{\mathrm{ud}}$. Although impressive, that result falls short of super-allowed nuclear beta decays where an order of magnitude better precision already exists. Here, we advocate a new strategy for utilizing pion beta decay, based on its utility in determining $V_{\mathrm{us}}/V_{\mathrm{ud}}$ via the ratio $R_V=\mathrm{\Gamma }(K\to \pi l\nu (\gamma ))/\mathrm{\Gamma }({\pi }^{+}\to {\pi }^0{e}^{+}\nu (\gamma ))$ which provides a measure of $f_{+}^K(0)|V_{\mathrm{us}}|/f_{+}^{\pi }(0)|V_{\mathrm{ud}}|$ independent of the Fermi constant and short-distance radiative corrections. Its dependence on the ratio of two hadronic vector current form factors provides an interesting computational goal for lattice gauge theory studies. Employing a recent lattice based value $f_{+}^K(0)/f_{+}^{\pi }(0)=0.970(2)$, we find $V_{\mathrm{us}}/V_{\mathrm{ud}}=0.22910(91)$ compared to $V_{\mathrm{us}}/V_{\mathrm{ud}}=0.23131(45)$ obtained from $R_A=\mathrm{\Gamma }(K\to \mu \nu (\gamma ))/\mathrm{\Gamma }(\pi \to \mu \nu (\gamma ))$. Those independent $V_{\mathrm{us}}/V_{\mathrm{ud}}$ determinations exhibit a $2.2\sigma$ discrepancy. That tension suggests a needed shift in the lattice $f_{+}^K(0)/f_{+}^{\pi }(0)$ value towards the consistency range 0.961(4), experimental/theory input changes or “new physics” effects. Other features and implications of $R_V$ and $R_A$ are also discussed.

We show that every compact, unitary two-dimensional conformal field theory with an Abelian conserved current has vanishing twist gap for charged primary fields with respect to the $\mathfrak{u}(1)\times \mathrm{Virasoro}$ algebra. This means that either the chiral algebra is enhanced by a charged primary field with zero twist or there is an infinite family of charged primary fields that accumulate to zero twist.

Following a series of similar calculations in simpler nonconformal holographic setups, we determine the quasinormal mode spectrum for an operator dual to a gauge-invariant scalar field within the improved holographic QCD framework. At temperatures somewhat above the critical temperature of the deconfinement transition, we find a small number of clearly separated modes followed by a branch-cut-like structure parallel to the real axis, the presence of which is linked to the form of the IHQCD potential employed. The temperature dependence of the lowest nonzero mode is furthermore used to study the thermalization time of the corresponding correlator, which is found to be of the order of the inverse critical temperature near the phase transition and decrease slightly faster than $1/T$ at higher temperatures.

We investigate the evolution of holographic entanglement entropy (HEE) and holographic complexity (HC) under a thermal quench in Einstein-Maxwell-axion theory, which is dual to a field theory with momentum relaxation on the boundary. A strip-shaped boundary geometry is utilized to calculate HEE and HC via “$\text{entropy}=\text{surface}$” and “$\text{complexity}=\text{volume}$” conjecture, respectively. By fixing other parameters, we claim that either large enough black hole charge or width of the strip will introduce swallow-tail behaviors in HEE and multivalues in HC due to the discontinuity of the minimum Hubeny-Rangamani-Takayanagi surface. Meanwhile, we explore the effects of momentum relaxation on the evolution of HEE and HC. The results present that the momentum relaxation will suppress the discontinuity to occur as it increases. For large enough momentum relaxation, the continuity of HEE and HC will be recovered.

Recently, Saad et al. showed how to define the genus expansion of Jackiw-Teitelboim (JT) quantum gravity in terms of a double-scaled Hermitian matrix model. However, the model’s nonperturbative sector has fatal instabilities at low energy that they be cured by procedures that render the physics nonunique. This might not be a desirable property for a system that is supposed to capture key features of quantum black holes. Presented here is a model with identical zperturbative physics at high energy that instead has a stable and unambiguous nonperturbative completion of the physics at low energy. An explicit examination of the full spectral density function shows how this is achieved. The new model, which is based on complex matrix models, also allows for the straightforward inclusion of spacetime features analogous to Ramond-Ramond fluxes. Intriguingly, there is a deformation parameter that connects this nonperturbative formulation of JT gravity to one which, at low energy, has features of a super JT gravity.

We improve the recently discovered upper and lower bounds on the $O(1)$ correction to the Cardy formula for the density of states integrated over an energy window (of width $2\delta$), centered at high energy in two-dimensional unitary and modular invariant conformal field theory. We prove optimality of the lower bound for $\delta \to 1^{-}$. We prove a conjectured upper bound on the asymptotic gap between two consecutive Virasoro primaries for a central charge greater than 1, demonstrating it to be 1. Furthermore, a systematic method is provided to establish a limit on how tight the bound on the $O(1)$ correction to the Cardy formula can be made using bandlimited functions. The techniques and the functions used here are of generic importance whenever the Tauberian theorems are used to estimate some physical quantities.

In this work, we consider local and nonlocal higher-derivative generalizations of the super-Chern-Simons theory and four-dimensional supersymmetric QED. In contrast to previous studies, the models studied here also have higher-derivative terms in the matter sector. For these models, we calculate the one-loop superfield effective potential.

We consider purely topological 2D Yang-Mills theory on a torus with the second Stiefel-Whitney class added to the Lagrangian in the form of a $\theta$ term. It will be shown that at $\theta =\pi$ there exists a class of $SU(2N)/{\mathbb{Z}}_2$ ($N>1$) gauge theories with a twofold degenerate vacuum, which spontaneously breaks the time reversal and charge conjugation symmetries. The corresponding order parameter is given by the generator $\mathcal{O}$ of the ${\mathbb{Z}}_N$ one-form symmetry.

In recent years, many examples appeared in the literature where the configuration entropy (CE), introduced by Gleiser and Stamatopoulos, plays the role of an indicator of stability of physical systems. It was observed that, comparing states of the same system, the lower is the value of the CE, the more stable is the state. In this work, we investigate the behavior of the differential configuration entropy (DCE), that is appropriate for systems with continuous degrees of freedom, in a new context. We consider quasistates of quarkonium (a vector meson made of a heavy quark antiquark pair) inside a plasma at finite density. It is known that the density increases the dissociation effect for quasiparticles inside a plasma. So, increasing the density of a thermal medium corresponds to reducing the stability of the quasiparticles. In order to investigate how this situation is translated in the configuration entropy context, we use a recently developed holographic anti–de Sitter/QCD model for heavy vector mesons. The quasinormal modes describing the quasistates are obtained and the corresponding DCE is calculated. We find, for bottomonium and charmonium $1S$ quasi-states, that the DCE increases with the quark density, or quark chemical potential, of the medium. This result shows that the DCE works again as an indicator of stability, represented in this case by the dissociation effect associated with the density.

We study the Schwinger effect in near-extremal nonrotating black holes in an arbitrary $D(\ge 4)$-dimensional asymptotically flat and (A)dS space. Using the near-horizon geometry ${\mathrm{AdS}}_2\times {\mathrm{S}}^{D-2}$ of near-extremal black holes with Myers-Perry metric, we find a universal expression of the emission formula for charges that is a multiplication of the Schwinger effects in an ${\mathrm{AdS}}_2$ space and in a two-dimensional Rindler space. The effective temperature of an accelerated charge for the Schwinger effect is determined by the radii of the effective ${\mathrm{AdS}}_2$ space and ${\mathrm{S}}^{D-2}$ as well as the mass, charge, angular momentum of the charge, and the radius of the (A)dS space. The Schwinger effect in the asymptotically flat space is more efficient and persistent for a wide range of large black holes for dimensions higher than four. The AdS (dS) boundary enhances (suppresses) the Schwinger effect than the asymptotically flat space. The Schwinger effect persists for a wide range of black holes in the AdS space and has an upper bound in the dS space.

The detection of gravitational wave signals by Advanced LIGO and Advanced Virgo enables us to probe the polarization content of gravitational waves. In general relativity, only tensor modes are present, while in a variety of alternative theories one can also have vector or scalar modes. Recently test were performed which compared Bayesian evidences for the hypotheses that either purely tensor, purely vector, or purely scalar polarizations were present. Indeed, with only three detectors in a network and allowing for mixtures of tensor polarizations and alternative polarization states, it is not possible to identify precisely which nonstandard polarizations might be in the signal and by what amounts. However, we demonstrate that one can still infer whether, in addition to tensor polarizations, alternative polarizations are present in the first place, irrespective of the detailed polarization content. We develop two methods to do this for sources with electromagnetic counterparts, both based on the so-called null stream. Apart from being able to detect mixtures of tensor and alternative polarizations, these have the added advantage that no waveform models are needed, and signals from any kind of transient source with known sky position can be used. Both formalisms allow us to combine information from multiple sources so as to arrive at increasingly more stringent bounds. For now we apply these on the binary neutron star signal GW170817, showing consistency with the tensor-only hypothesis with p-values of 0.315 and 0.790 for the two methods.

We describe a framework for a generalized nonlocal gravity theory inspired by Poincaré gauge theory. Our theory provides a unified description of previous nonlocal extensions of Einstein’s theory of gravitation, in particular it allows for a clear geometrical foundation. Furthermore, it incorporates recent simplifications for the ansatz of the nonlocality, which should allow for a systematic study of the impact of nonlocal concepts on observations.

We study gravitational waves from a hierarchical three-body system up to first-order post-Newtonian approximation. Under certain conditions, the existence of a nearby third body can cause periodic exchange between eccentricity of an inner binary and relative inclination, known as Kozai-Lidov oscillations. We analyze features of the waveform from the inner binary system undergoing such oscillations. We find that variation caused due to the tertiary companion can be observed in the gravitational waveforms and energy spectra, which should be compared with those from isolated binaries and coplanar three-body system. The detections from future space-based interferometers will make possible the investigation of gravitational wave spectrum in mHz range and may fetch signals by sources addressed.