High-energy heavy-ion collisions generate an extremely strong magnetic field which plays a key role in a number of novel quantum phenomena in quark-gluon plasma (QGP), such as the chiral magnetic effect. However, due to the complexity in theoretical modelings of the coupled electromagnetic fields and the QGP system, especially in the preequilibrium stages, the lifetime of the magnetic field in the QGP medium remains undetermined. We establish, for the first time, a kinetic framework to study the dynamical decay of the magnetic field in the early stages of a weakly coupled QGP by solving the coupled Boltzmann and Maxwell equations. We find that at late times a magnetohydrodynamical description of the coupled system emerges. With respect to realistic collisions at RHIC and the LHC, we estimate the residual strength of the magnetic field in the QGP when the system starts to evolve hydrodynamically.

Green functions scattering method is generalized to consider mixing of electromagnetic polarizations after reflection from the plane boundary between different media and applied to derivation of the Casimir-Polder potential in systems with Chern-Simons plane boundary layers. The method is first applied to derive the Casimir-Polder potential of an anisotropic atom in the presence of a Chern-Simons plane boundary layer on a dielectric half-space. Then a general result for the Casimir-Polder potential of an anisotropic atom between two dielectric half-spaces with Chern-Simons plane parallel boundary layers is derived. The Casimir-Polder potential of an anisotropic atom between two Chern-Simons plane parallel layers in vacuum is expressed through special functions. Novel P-odd three-body vacuum effects are discovered and analyzed in the system of two Chern-Simons plane parallel layers and a neutral atom in its ground state between the layers. Remarkably, P-odd three-body vacuum effects arising due to 180 degree rotation of one of the Chern-Simons layers can be verified in experiments with neutral atoms having QED dipole interaction with an electromagnetic field.

We discuss the construction of a free scalar quantum field theory on $\kappa$-Minkowski noncommutative spacetime. We do so in terms of $\kappa$-Poincaré-invariant $N$-point functions, i.e., multilocal functions which respect the deformed symmetries of the spacetime. As shown in a previous paper by some of us, this is only possible for a lightlike version of the commutation relations, which allow the construction of a covariant algebra of $N$ points that generalizes the $\kappa$-Minkowski commutation relations. We solve the main shortcoming of our previous approach, which prevented the development of a fully covariant quantum field theory: the emergence of a non-Lorentz-invariant boundary of momentum space. To solve this issue, we propose to “extend” momentum space by introducing a class of new Fourier modes and we prove that this approach leads to a consistent definition of the Pauli-Jordan function, which turns out to be undeformed with respect to the commutative case. We finally address the quantization of our scalar field and obtain a deformed, $\kappa$-Poincaré-invariant, version of the bosonic oscillator algebra.

Gravitational-wave tails are linear waves that backscatter on the curvature of space-time generated by the total mass energy of the source. The nonlinear memory effect arises from gravitational waves sourced by the stress-energy distribution of linear waves themselves. These two effects are due to quadratic multipolar interactions (mass quadrupole and quadrupole quadrupole) and are well known. Also known are the tails generated by tails themselves (cubic “tails of tails”) and the tails generated by tails of tails or vice versa (quartic “tails of tails of tails”). In this work, we focus on the cubic “tails of memory” corresponding to the mass-quadrupole-quadrupole interaction, as well as the “spin-quadrupole tails,” which are due to the cubic interaction between the mass, the total angular momentum and the quadrupole. The tails of memory and the spin-quadrupole tails contribute to the asymptotic waveform at the fourth-post-Newtonian order beyond quadrupolar radiation.

The intermediate mass black hole range, ${10}^2\lesssim M_{\mathrm{BH}}/M_{\odot }\lesssim {10}^5$, has long offered enticing possibilities for primordial black holes (PBHs), with populations in this range postulated to be responsible for some of the black hole binary merger detected events as well as the existence of supermassive black holes embedded at galactic centers. However, a prominent bound derived from PBH accretion during recombination severely restricts the mass fraction of intermediate mass PBHs. We address this problem by proposing a formation scenario in which “primordial” black holes form late in our cosmological history, beyond the cosmic microwave background era, and bypassing this bound. During this crucial epoch, our population of compact objects exist as thermal balls supported by thermal pressure, which eventually cool to Fermi balls supported by degeneracy pressure and finally collapse to PBHs. Our mechanism is a viable production method for both the mass gap LIGO-VIRGO-KAGRA detections and the James Webb Space Telescope observation of an early time $z>10$ supermassive black hole. Furthermore, we present the remarkable possibility of PBH formation after the present era, which we term future PBH. Such a population would evade most, if not all, bounds on the PBH mass spectrum in the literature and open up previously unthought-of possibilities. Light future PBHs could form below the Hawking evaporation threshold and convert the bulk of the matter in the Universe into radiation.

We present a relativistic disk-corona model for a steady state advective accretion disk to explain the UV to x-ray spectral index ${\alpha }_{\mathrm{OX}}$ evolution of four tidal disruption event (TDE) sources XMMSL2J1446, XMMSL1J1404, XMMSL1J0740, and AT2018fyk. The viscous stress in our model depends on gas ($P_g$) and total ($P_t$) pressures as ${\tau }_{r\varphi }\propto P_g^{\mu }{P}_t^{1-\mu }$, where $\mu$ is a constant. We compare various steady and time-dependent sub-Eddington TDE accretion models along with our disk-corona model to the observed ${\alpha }_{\mathrm{OX}}$ of TDE sources and find that the disk-corona model agrees with the observations better than the other models. We find that $\mu$ is much smaller than unity for TDE sources XMMSL2J1446, XMMSL1J1404, and XMMSL1J0740. We also compare the relativistic model with a nonrelativistic disk-corona model. The relativistic accretion dynamics reduce the spectral index relative to the nonrelativistic accretion by increasing the energy transport to the corona. We estimate the mass accretion rate for all the sources and find that the observed luminosity follows a nearly linear relation with the mass accretion rate. The ratio of x-ray luminosity from the disk to the corona increases with the mass accretion rate. The observed ${\alpha }_{\mathrm{OX}}$ shows positive and negative correlations with luminosity. The disk-corona model explains the negative correlation seen in the TDE sources XMMSL1J0740, XMMSL2J1446, and XMMSL1J1404. However, TDE AT2018fyk shows a positive correlation at higher luminosity and shows a better fit when a simple spherical adiabatic outflow model is added to the relativistic disk-corona model. Even though the disk luminosity dominates at a higher mass accretion rate, we show that the accretion models without a corona are unable to explain the observations, and the presence of a corona is essential.

We evaluate the prospects for radio follow-up of the double neutron stars (DNSs) in the Galactic disk that could be detected through future space-borne gravitational wave (GW) detectors. We first simulate the DNS population in the Galactic disk that is accessible to space-borne GW detectors according to the merger rate from recent LIGO results. Using the inspiraling waveform for the eccentric binary, the average number of the DNSs detectable by TianQin (TQ), LISA, and $\mathrm{TQ}+\mathrm{LISA}$ are 217, 368, and 429, respectively. For the joint GW detection of $\mathrm{TQ}+\mathrm{LISA}$, the forecasted parameter estimation accuracies, based on the Fisher information matrix, for the detectable sources can reach the levels of $\mathrm{\Delta }{P}_{\mathrm{b}}/P_{\mathrm{b}}\lesssim {10}^{-6}$, $\mathrm{\Delta }\mathrm{\Omega }\lesssim 100{\mathrm{deg}}^2$, $\mathrm{\Delta }e/e\lesssim 0.3$, and $\mathrm{\Delta }{\dot{P}}_{\mathrm{b}}/{\dot{P}}_{\mathrm{b}}\lesssim 0.02$. These estimation accuracies are fitted in the form of power-law function of signal-to-noise ratio. Next, we simulate the radio pulse emission from the possible pulsars in these DNSs according to pulsar beam geometry and the empirical distributions of spin period and luminosity. For the DNSs detectable by $\mathrm{TQ}+\mathrm{LISA}$, the average number of DNSs detectable by the follow-up pulsar searches using the Parkes, FAST, SKA1, and SKA are 8, 10, 43, and 87, respectively. Depending on the radio telescope, the average distances of these GW-detectable pulsar binaries vary from 1 to 7 kpc. Considering the dominant radiometer noise and phase jitter noise, the timing accuracy of these GW-detectable pulsars can be as low as 70 ns while the most probable value is about $100\mathrm{\mu }\mathrm{s}$.

We study the possibility that the axion Peccei-Quinn symmetry is spontaneously broken after the beginning of inflation. This scenario interpolates between preinflationary and postinflationary axion cosmology with significant phenomenological differences from both. Since the axion is not present at the early stages of inflation large inflationary fluctuations are produced only at scales not constrained by cosmic microwave background (CMB), avoiding the strongest isocurvature constraints. The energy density in isocurvature perturbations at short scales however can be comparable with the adiabatic contribution from misalignment. These large overdensities can lead to the formation of axion miniclusters and also to constraints from Lyman-$\alpha$ forest and future CMB spectral distortion measurements. If Peccei-Quinn symmetry is broken during the first O(25) $e$-foldings of inflation no axions are produced from the string network but contributions from the annihilation of domain walls can further boost the abundance. This scenario is minimally realized if the Hubble scale during inflation drops below the Peccei-Quinn symmetry breaking scale but other realizations are possible.

We consider the sterile neutrino, which is also known as heavy neutral lepton, interacting with the Standard Model (SM) active neutrino and photon via a transition magnetic moment, the so-called dipole portal, which can be induced from the more general dipole couplings which respect the full gauge symmetries of the SM. Depending on the interactions with $\mathrm{SU}(2{)}_L$ and ${\mathrm{U}(1)}_Y$ field strength tensors ${\mathcal{W}}_{\mu \nu }^a$ and $B^{\mu \nu }$, we consider four typical scenarios and probe the constraints on the couplings with photon $d_{\gamma }$ at LEP using the analyses to search monophoton signature and the measurement of $Z$ decay. We find that in the considered scenarios assuming the coupling with $Z$ boson $d_Z\ne 0$, the measurement of $Z$ decaying into photon plus invisible particles can provide stricter constraints than the monophoton searches at the LEP1. The complementary constraints to existing experiments can be provided by the LEP. We also investigate the sensitivity on the dipole portal coupling $d_{\gamma }$ from the monophoton searches at future electron colliders, such as CEPC, and find that CEPC can explore the previously unconstrained parameter space by current experiments.

We perform the first lattice study on the mixing of the isoscalar pseudoscalar meson $\eta$ and the pseudoscalar glueball $G$ in the $N_f=2$ QCD at the pion mass $m_{\pi }\approx 350\mathrm{MeV}$. The $\eta$ mass is determined to be $m_{\eta }=714(6)(16)\mathrm{MeV}$. Through the Witten-Veneziano relation, this value can be matched to a mass value of $\sim 981\mathrm{MeV}$ for the SU(3) counterpart of $\eta$. Based on a large gauge ensemble, the $\eta -G$ mixing energy and the mixing angle are determined to be $|x|=107(15)(2)\mathrm{MeV}$ and $|\theta |=3.46(46)°$ from the $\eta -G$ correlators that are calculated using the distillation method. We conclude that the $\eta -G$ mixing is tiny and the topology induced interaction contributes most of $\eta$ mass owing to the QCD ${\mathrm{U}}_{\mathrm{A}}(1)$ anomaly.

Dipole polarizabilities of light pseudoscalar mesons are calculated in the framework of the mean field approach to QCD vacuum and bosonization based on the statistical ensemble of almost everywhere homogeneous Abelian (anti-)self-dual gluon fields, the domain model of QCD vacuum. In this approach, a nonlocal effective action of meson fields is derived that describes all possible strong, weak, and electromagnetic interactions of meson fields including their excited states. The considered mean field implements confinement and chiral symmetry, which manifests itself both in the properties of quark and gluon fields as well as upon bosonization, in the mass spectrum, decays constants and form factors of nonlocal colorless hadrons, and leads to the qualitatively distinctive features of the effective meson action. Particularly relevant to the subject of the present paper are the nonlocality of meson-quark-antiquark vertices and the absence of poles at real momenta in the propagators of scalar meson fields composed of light quark-antiquark pairs. In view of this, studying the role of manifest nonlocality of mesons and contribution of intermediate scalar meson fields in formation of the polarizabilities is of special interest. It turns out that, for charged pions and kaons, this contribution is substantial but not the largest one. Nonlocal nature of mesons provides an additional contribution so that calculated polarizabilities are in reasonable agreement with COMPASS experimental data and chiral perturbation theory.

The target normal single-spin asymmetry in inclusive electron-nucleon scattering is studied in the low-energy regime that includes the $\mathrm{\Delta }$ resonance. The particular interest in the asymmetry resides in that it is driven by two-photon exchange effects. It probes the spin-dependent absorptive part of the two-photon exchange amplitude, which is free of infrared and collinear singularities and represents the most pristine expression of two-photon exchange dynamics. The study presented here uses the $1/N_c$ expansion of QCD, which combines the $N$ and $\mathrm{\Delta }$ through the emergent $SU(4)$ spin-flavor symmetry in the baryon sector and allows for a systematic construction of the transition electromagnetic (EM) currents. The analysis includes the first subleading corrections in the $1/N_c$ expansion and presents results for elastic and inelastic final states. The asymmetry is found to be in the range ${10}^{-3}-{10}^{-2}$. The $\mathrm{\Delta }$ resonance plays an important role as an intermediate state in the elastic asymmetry and as a final state in the inclusive asymmetry.

We study two quark-propagator meromorphic Ansätze that admit a clear connection between calculations in Euclidean space and Minkowski spacetime. The connection is established through a modified Wick rotation in momentum space, where the integration contour along the imaginary axis is adequately deformed. The Ansätze were previously proposed in the literature and fitted to Euclidean lattice QCD data. The generalized impulse approximation is used to calculate the pion transition form factor and electromagnetic form factor, correcting an earlier result. The pion decay constant and distribution amplitude are also calculated. The latter is used to deduce the asymptotic behavior of the form factors. Such an asymptotic behavior is compared with those obtained directly from the generalized impulse approximation and the causes of differences are pointed out.

This work is a continuation in our series of papers that addresses quark models of hadronic structure on the light front, motivated by the QCD vacuum structure and lattice results. The spontaneous breaking of chiral symmetry on the light front is shown to parallel that in the rest frame, where the nonlocal instanton induced ’t Hooft interaction plays a central role. By rewriting this interaction solely in terms of the good component of the fermionic field, a scalar chiral condensate emerges in the mean-field approximation, which is identical to the one obtained in the rest frame. The pions and kaons emerge as deeply bound Goldstone modes in the chiral limit, with the scalar-isoscalar sigma meson mode as a threshold state with zero binding. We explicitly derive the light front distribution amplitudes (DAs) and parton distribution functions (PDFs) for these mesons. The DAs and PDFs are in good agreement with those extracted from the QCD instanton vacuum in the rest frame, using the large momentum effective theory (LaMET). The QCD evolved DAs and PDFs compare well with available measurements, as well as recent lattice results.

We extend our studies of a new class of $2\to 3$ exclusive processes using the collinear factorization framework by considering the exclusive photoproduction of a $\gamma \rho$ pair, in the kinematics where the pair has a large invariant mass, and the outgoing $\rho$ meson has a sufficiently large transverse momentum to not resonate with the nucleon. We cover the whole kinematical range from medium energies in fixed-target experiments to very large energies of colliders, by considering the experimental conditions of JLab 12-GeV, COMPASS, and future EIC and LHC (in ultra-peripheral collisions) cases. One of the main interests in studying the present process is that it provides access to both chiral-even and chiral-odd generalized parton distributions, depending on the polarization of the outgoing $\rho$ meson, both at leading twist. Our analysis covers both neutral and charged $\rho$ mesons. We find that the orders of magnitude of the obtained cross sections are sufficiently large for a dedicated experimental analysis to be performed, especially at JLab, for both longitudinally and transversely polarized $\rho$. Furthermore, we compute the linear photon beam polarization asymmetry which is sizable for a longitudinally polarized meson. These predictions are obtained for both the asymptotic distribution amplitude (DA) and the holographic DA.

The (anti)neutrino nucleus scattering plays a very important role in probing the hadronic structure as well as the electroweak phenomenologies. To this end, we calculate the jet production semi-inclusive deeply inelastic (anti)neutrino nucleus scattering process. The initial (anti)neutrino is assumed to be scattered off by a target particle with spin $1/2$ or 1. Due to the limitation of the factorization theorem, calculations are carried out in the QCD parton model framework up to tree level twist-3. We consider both the neutral current and the charged current processes and write them into a unified form due to the similar interaction forms. Considering the angular modulations and polarizations of the cross section, we calculate the complete azimuthal asymmetries. We also calculate the intrinsic asymmetries which reveal the imbalance in the distribution of the intrinsic transverse momentum of the quark. We find that these asymmetries can be expressed in terms of the transverse momentum-dependent parton distribution functions (TMD PDFs) and the electroweak couplings. With the determined couplings, these asymmetries can be used to extract the TMD PDFs and further to study the nucleus structures.

We elaborate on the off-shell superspace construction of curvature-squared invariants in minimal five-dimensional supergravity. This is described by the standard Weyl multiplet of conformal supergravity coupled to two compensators being a vector multiplet and a linear multiplet. In this setup, we review the definition of the off-shell two-derivative gauged supergravity together with the three independent four-derivative superspace invariants defined in Butter et al. [J. High Energy Phys. 02 (2015) 111]. We provide the explicit expression for the linear multiplet based on a prepotential given by the logarithm of the vector multiplet primary superfield. We then present for the first time the primary equations of motion for minimal gauged off-shell supergravity deformed by an arbitrary combination of these three four-derivative locally superconformal invariants. We also identify a four-derivative invariant based on the linear multiplet compensator and the kinetic superfield of a vector multiplet, which can be used to engineer an alternative supersymmetric completion of the scalar curvature squared.

We construct a new family of ${\mathrm{AdS}}_2\times S^3\times S^2$ solutions to type IIB supergravity arising as near-horizon geometries of D1-F1-D3-D5-NS5-D7 brane intersections preserving four supersymmetries. We show that a subclass of these solutions asymptotes locally to the ${\mathrm{AdS}}_6\times S^2\times {\mathrm{\Sigma }}_2$ solution to type IIB supergravity holographically dual to the five-dimensional Sp(N) fixed point theory. This suggests that these solutions can be interpreted as D1-F1-D3 line defects within this CFT. Switching off the D7-branes, we act with $\mathrm{SL}(2,\mathbb{R})$ to construct a second family of solutions that can be related to an ${\mathrm{AdS}}_3\times S^3\times S^3$ class of M-theory backgrounds describing surface defects within the six-dimensional (1,0) SCFT dual to ${\mathrm{AdS}}_7/{\mathbb{Z}}_k\times S^4$. Finally, using non-Abelian T-duality we construct new classes of ${\mathrm{AdS}}_2\times S^2\times S^2$ solutions to type IIA supergravity with four supercharges and elaborate on their M-theory origin.

We investigate how dark energy affects atom-field interaction. To this end, we consider acceleration radiation of a freely falling atom close to a Schwarzschild black hole (BH) in the presence of dark energy characterized by a positive cosmological constant $\mathrm{\Lambda }$. The resulting spacetime is endowed with a BH and a cosmological (or de Sitter) horizon. Our consideration is a nonextremal ($1+1$)-dimensional geometry with horizons far apart, giving rise to a flat Minkowski-like region in between the two horizons. Assuming a scalar (spin-0) field in a Boulware-like vacuum state, and by using a basic quantum optics approach, we numerically achieve excitation probabilities for the atom to detect a photon as it falls toward the BH horizon. It turns out that the nature of the emitted radiation deeply drives its origin from the magnitude of $\mathrm{\Lambda }$. In particular, radiation emission is enhanced due to dilation of the BH horizon by dark energy. Also, we report an oscillatory nonthermal spectrum in the presence of $\mathrm{\Lambda }$, and these oscillations, in a varying degree, also depend on BH mass and atomic excitation frequency. We conjecture that such a hoedown may be a natural consequence of a constrained motion due to the bifurcate Killing horizon of the given spacetime. The situation is akin to the Parikh-Wilzcek tunneling approach to Hawking radiation where the presence of extra contributions to the Boltzmann factor deforms the thermality of flux. It apparently hints at field satisfying a modified energy-momentum dispersion relation within classical regime of general relativity arising as an effective low energy consequence of an underlying quantum gravity theory. Our findings may signal new ways of conceiving the subtleties surrounding the physics of dark energy.