The study of medium effects on properties of particles embedded in nuclear matter is of great importance for understanding the nature and internal quark-gluon organization as well as exact determination of the quantum numbers, especially of the exotic states. In this context, we study the physical properties of one of the famous charmoniumlike states, $Z_c(3900)$, in a cold dense matter. We investigate the possible shifts in the mass and current-meson coupling of the $Z_c(3900)$ state due to the dense medium at saturation density ${\rho }^{\text{sat}}$ by means of the in-medium sum rules. We also estimate the vector self-energy of this state at saturation nuclear matter density. We discuss the behavior of the spectroscopic parameters of this state with respect to the density up to a high density corresponding to the core of neutron stars, $\rho \approx 5{\rho }^{\text{sat}}$. Both the mass and current coupling of this state show nonlinear behavior and decrease with respect to the density of the medium: the mass reaches roughly 30% of its vacuum value at $\rho =5{\rho }^{\text{sat}}$, while the current coupling approaches zero at $\rho \approx 2.1{\rho }^{\text{sat}}$, when the central values of the auxiliary and other input parameters are used.

We study the fine structure in the spectrum of known and predicted negative-parity hidden-charm exotic meson states, which comprise the lowest $P$-wave multiplet in the dynamical diquark model. Starting with a form previously shown to successfully describe the $S$-wave states, we develop a 5-parameter Hamiltonian that includes spin-orbit and tensor terms. After discussing the experimental status of the observed $J^{PC}=1^{--}$ states $Y$ with respect to masses and decay modes (classified by eigenvalues of heavy-quark spin), we note a number of inconsistencies between measurements from different experiments that complicate a unique determination of the spectrum. Outlining a variety of scenarios for interpreting the $Y$ data, we perform fits to each one, obtaining results that demonstrate differing possibilities for the $P$-wave spectra. Choosing one of these fits for illustration, we predict masses for all 28 isomultiplets in this $1P$ multiplet, compare the results to tantalizing hints in the data, and discuss the rich discovery potential for new states.

In this work, we study the mass spectrum of the ${\mathrm{\Omega }}_{ccc}$ and ${\mathrm{\Omega }}_{bbb}$ baryons up to the $N=2$ shell within a nonrelativistic constituent quark model. The model parameters are adopted to be the determinations by fitting the charmonium and bottomonium spectra in our previous works. The masses of the ${\mathrm{\Omega }}_{ccc}$ and ${\mathrm{\Omega }}_{bbb}$ baryon states predicted in the present work reasonably agree with the results obtained with the lattice QCD calculations. Furthermore, to provide more knowledge of the ${\mathrm{\Omega }}_{ccc}$ and ${\mathrm{\Omega }}_{bbb}$ states, we evaluate their radiative decays with the available masses and wave functions from the potential model.

We provide the first steps toward a flat space holographic correspondence in two bulk spacetime dimensions. The gravity side is described by a conformally transformed version of the matterless Callan-Giddings-Harvey-Strominger model. The field theory side follows from the complex Sachdev-Ye-Kitaev model in the limit of large specific heat and vanishing compressibility. We derive the boundary action analogous to the Schwarzian as the key link between gravity and field theory sides and show that it coincides with a geometric action discovered recently by one of us [H. R. Afshar, Warped Schwarzian theory, J. High Energy Phys. 02 (2020) 126].

We present a general prescription for determining the global $U(1)$ symmetries of six-dimensional superconformal field theories. We use the quiverlike gauge theory description of the tensor branch to identify candidate $U(1)$ symmetries which can act on generalized matter. The condition that these candidate $U(1)$’s are free of Adler-Bell-Jackiw anomalies provides bottom-up constraints for $U(1)$’s. This agrees with the answer obtained from symmetry breaking patterns induced by Higgs branch flows. We provide numerous examples illustrating the details of this proposal. In the F-theory realization of these theories, some of these symmetries originate from deformations of non-Abelian flavor symmetries localized on a component of the discriminant, while others come from an additional generator of the Mordell-Weil group. We also provide evidence that some of these global $U(1)$’s do not arise from gauge symmetries, as would happen in taking a decoupling limit of a model coupled to six-dimensional supergravity.

We formulate supersymmetric non-Hermitian quantum field theories with $\mathcal{P}\mathcal{T}$ symmetry, starting with free chiral boson/fermion models and then including trilinear superpotential interactions. We consider models with both Dirac and Majorana fermions, analyzing them in terms of superfields and at the component level. We also discuss the relation between the equations of motion, the (non)invariance of the Lagrangian and the (non)conservation of the supercurrents in the two models. We exhibit a similarity transformation that maps the free-field supersymmetric $\mathcal{P}\mathcal{T}$-symmetric Dirac model to a supersymmetric Hermitian theory, but there is, in general, no corresponding similarity transformation for the Majorana model. In this model, we find generically a mass splitting between bosons and fermions, even though its construction is explicitly supersymmetric, offering a novel non-Hermitian mechanism for soft supersymmetry breaking.

We study the Schwinger effect in near-extremal Reissner-Nordström black holes with electric and/or magnetic charges in (anti-)de Sitter (AdS) space. The formula for the Schwinger effect takes a universal form for near-extremal black holes with the near-horizon geometry of ${\text{AdS}}_2\times S^2$ and with the proper radii for the ${\text{AdS}}_2$ space and the two-sphere $S^2$, regardless of the asymptotically flat or (A)dS space. The asymptotic AdS boundary enhances and the dS boundary suppresses the Schwinger effect, and the small radius of AdS (dS) space reinforces the enhancement and suppression.

We examine the self-consistency of the first-order formulation of the Yang-Mills theory. By comparing the generating functional $Z$ before and after integrating out the additional field $F_{\mu \nu }^a$, we derive a set of structural identities that must be satisfied by the Green’s functions at all orders. These identities, which hold in any dimension, are distinct from the usual Ward identities and are necessary for the internal consistency of the first-order formalism. They relate the Green’s functions involving the fields $F_{\mu \nu }^a$, to Green’s functions in the second-order formulation which contain the gluon strength tensor $f_{\mu \nu }^a$. In particular, such identities may provide a simple physical interpretation of the additional field $F_{\mu \nu }^a$.

The purpose of this article is twofold. First, we highlight a simple connection between the real part of quasinormal modes (QNMs) in the eikonal limit and the shadow radius of black holes (BHs) and then explore the effect of dark matter on the QNMs of massless scalar field and electromagnetic field perturbations in a BH spacetime surrounded by perfect fluid dark matter (BHPFDM). Using the Wentzel–Kramers–Brillouin (WKB) approximation, we show that the quasinormal mode spectra of BHPFDM deviate from those of Schwarzschild black hole due to the presence of the perfect fluid dark matter (PFDM) encoded by the parameter $k$. Moreover, it is shown that for any $k>0$ the real part and the absolute value of the imaginary part of QNM frequencies increases, and this means that the field perturbations in the presence of PFDM decay more rapidly compared to the Schwarzschild vacuum BH. We point out that there exists a reflecting point $k_0$ corresponding to maximal values for the real part of QNM frequencies. Namely, as the PFDM parameter $k$ increases in the interval $k<k_0$, the QNM frequencies increases and reach their maximum values at $k=k_0$. Finally, we show that $k_0$ is also a reflecting point for the shadow radius, while this conclusion can be deduced directly from the inverse relation between the real part of QNMs and the shadow radius.

In odd space-time dimensions, the retarded solution of the massless wave equation has support not only on the light cone, but also inside it. At the same time, a free massless field should propagate at the speed of light. The mismatch of these two features is resolved by the fact that the emitted part of the field in the wave zone depends on the history of motion up to the retarded moment of proper time. It is shown that in the case of circular motion with an ultrarelativistic velocity, the main contribution to the radiation amplitude is made by a small interval of proper time preceding the retarded time, and thus the tail term is effectively localized. We obtain a tentative formula for scalar synchrotron radiation in $D$ dimensions: $P=g^2({\omega }_0{\gamma }^2/\sqrt{3}{)}^{D-2}$, which is explicitly verified in $D=3$, 4, 5.

LISA can detect higher harmonics of the ringdown gravitational-wave signal from massive black-hole binary mergers with large signal-to-noise ratio. The most massive black-hole binaries are more likely to have electromagnetic counterparts, and the inspiral will contribute little to their signal-to-noise ratio. Here we address the following question: can we extract the binary parameters and localize the source using LISA observations of the ringdown only? Modulations of the amplitude and phase due to LISA’s motion around the Sun can be used to disentangle the source location and orientation when we detect the long-lived inspiral signal, but they cannot be used for ringdown-dominated signals, which are very short lived. We show that (i) we can still measure the mass ratio and inclination of high-mass binaries by carefully combining multiple ringdown harmonics, and (ii) we can constrain the sky location and luminosity distance by relying on the relative amplitudes and phases of various harmonics, as measured in different LISA channels.

This paper introduces an analytical treatment of accelerated and geodesic motion within the framework of the Friedmann-Lemaître-Robertson-Walker (FLRW) spacetime. By employing conformal time transformations we manage to convert second order differential equations of motion in FLRW spacetime to first order equations in the conformally transformed spacetime. This allows us to derive a general analytical solution in closed-form for accelerated motion in spatially curved FLRW spacetime. We provide few examples of this general solution. The last part of our work focuses on the return journey for a traveler exploring a FLRW universe. We derive certain conditions for a de Sitter universe that have to be satisfied in order to achieve a return journey.

The ultraslow-roll (USR) inflationary models predict large-amplitude scalar perturbations at small scales which can lead to the primordial black hole production and scalar-induced gravitational waves. In general, scalar perturbations in the USR models can only be obtained using a numerical method because the usual slow-roll approximation breaks. In this work, we propose an analytical approach to estimate the scalar spectrum which is consistent with the numerical result. We find that the USR inflationary models predict a peak with power-law slopes in the scalar spectrum and energy spectrum of gravitational waves, and we derive the expression of the spectral indexes in terms of the inflationary potential. In turn, the inflationary potential near the USR regime can be reconstructed from the negative spectral index of the gravitational wave energy spectrum.

New viscous neutrino-radiation hydrodynamics simulations are performed for accretion disks surrounding a spinning black hole with low mass $3M_{\odot }$ and dimensionless spin 0.8 or 0.6 in full general relativity, aiming at modeling the evolution of a merger remnant of massive binary neutron stars or low-mass black hole–neutron star binaries. We reconfirm the following results found by previous studies of other groups: 15%–30% of the disk mass is ejected from the system with the average velocity of $\sim 5\%–10\%$ of the speed of light for the plausible profile of the disk as merger remnants. In addition, we find that for the not extremely high viscous coefficient case, the neutron richness of the ejecta does not become very high, because weak interaction processes enhance the electron fraction during the viscous expansion of the disk before the onset of the mass ejection, resulting in the suppression of the lanthanide synthesis. For high-mass disks, the viscous expansion timescale is increased by a longer-term neutrino emission, and hence, the electron fraction of the ejecta becomes even higher. We also confirm that the mass distribution of the electron fraction depends strongly on the magnitude of the given viscous coefficient. This demonstrates that a first-principle magnetohydrodynamics simulation is necessary for black hole–disk systems with sufficient grid resolution and with sufficiently long timescale (longer than seconds) to clarify the nucleosynthesis and electromagnetic signals from them.

We consider an inelastic scattering of protons within the simplest real scalar model ${\varphi }^3$ (phi-cubed). Although this model has been studied for a very long time, the problem of accounting for the interference contributions for all the possible particle multiplicities observed in experiments is not solved yet. We propose a method which is based on grouping of the interference contributions into sets in such a way that the sum of all interference contributions of each particular set can be calculated with Laplace’s method. This approach allowed us to calculate all the interference contributions to the cross sections for multiplicities up to $n\sim 50$ at the energy $\sqrt{s}\sim 50\mathrm{GeV}$. The obtained models of the energy dependence of the total $pp$ scattering cross section and the inclusive rapidity distribution are in qualitative agreement with the experiment. We also consider the well-known effect of the energy dependence of the shape of inclusive rapidity distribution and propose an explanation for this dependence and consider it exactly as the interference effect.

We study the anomalous $W^{+}{W}^{-}V$ ($V=\gamma$, $Z$) couplings in $e^{+}{e}^{-}\to W^{+}{W}^{-}$ using the complete set of polarization observables of $W$ boson with longitudinally polarized electron ($e^{-}$) and positron ($e^{+}$) beams. For the effective $W^{+}{W}^{-}V$ couplings, we use the most general Lorentz invariant form factor parametrization as well as $SU(2)\times U(1)$ invariant dimension-6 effective operators. We estimate simultaneous limits on the anomalous couplings using the Markov-chain Monte Carlo method for an $e^{+}{e}^{-}$ collider running at the center of mass energy of $\sqrt{s}=500\mathrm{GeV}$ and the integrated luminosity of $\mathcal{L}=100{\mathrm{fb}}^{-1}$, $3.2{\mathrm{ab}}^{-1}$ and $4{\mathrm{ab}}^{-1}$. The best limits on the anomalous couplings are obtained for $e^{-}$ and $e^{+}$ polarization being $(\pm 0.8,\mp 0.6)$ for both $100{\mathrm{fb}}^{-1}$ and $3.2{\mathrm{ab}}^{-1}$ of luminosity.

The LHCb collaboration, using its full data set from runs 1 and 2, announced in 2019 a surprising update of the hidden-charm pentaquark states $P_c(4380{)}^{+}$ and $P_c(4450{)}^{+}$, observed in 2015. A new state, $P_c(4312{)}^{+}$, was clearly seen at lower energies; furthermore, the original $P_c(4450)$ resonance was resolved into two individual states, named the $P_c(4440{)}^{+}$ and the $P_c(4457{)}^{+}$. Motivated by the fact that these new hidden-charm pentaquark states were successfully predicted by our chiral quark model, we extend herein such study to the doubly charmed sector. The analyzed total spin and parity quantum numbers are $J^P={\frac{1}{2}}^{-}$, ${\frac{3}{2}}^{-}$ and ${\frac{5}{2}}^{-}$, in the $I=\frac{1}{2}$ and $\frac{3}{2}$ isospin channels. We find several possible narrow baryon-meson resonances (theoretical masses in parenthesis): $I{J}^P=\frac{1}{2}{\frac{1}{2}}^{-}$ ${\mathrm{\Sigma }}_{c}D(4356)$, $\frac{1}{2}{\frac{3}{2}}^{-}$ ${\mathrm{\Sigma }}_c^{*}D(4449)$, $\frac{3}{2}{\frac{1}{2}}^{-}$ ${\mathrm{\Sigma }}_{c}D(4431)$, $\frac{3}{2}{\frac{1}{2}}^{-}$ ${\mathrm{\Sigma }}_{c}D(4446)$, $\frac{3}{2}{\frac{3}{2}}^{-}$ ${\mathrm{\Sigma }}_c{D}^{*}(4514)$ and $\frac{3}{2}{\frac{5}{2}}^{-}$ ${\mathrm{\Xi }}_{cc}^{*}\rho (4461)$ whose widths are 4.8, 8.0, 2.6, 2.2, 4.0 and 3.0 MeV, respectively. Moreover, one shallow bound state is found, too, with quantum numbers $I{J}^P=\frac{1}{2}{\frac{3}{2}}^{-}$ ${\mathrm{\Xi }}_{cc}^{*}\pi (3757)$. These doubly charmed pentaquark states are expected to be identified in future experiments.

In this paper, we follow a “bottom-up” anti–de Sitter (AdS)/QCD approach to holographically probe the dynamics of a moving $q\overline{q}$ pair inside a strongly coupled plasma at the boundary. We consider a deformed AdS-Reissner Nordström metric in the bulk in order to introduce nonconformality and finite quark density in the dual field theory. By boosting the gravity solution in a specific direction, we consider two extreme cases of orientation, parallel and perpendicular, for the Wilson loop, which in turn fixes the relative position of the $q\overline{q}$ pair with respect to the direction of boost in the plasma. By utilizing this setup, we holographically compute the vacuum expectation value of the timelike Wilson loop in order to obtain the real part of the $q\overline{q}$ potential, and the effects of nonconformality (deformation parameter $c$), the chemical potential $\mu$, and rapidity $\beta$ are observed on this potential. We then compute the in-medium energy loss of the moving parton (jet quenching parameter $q_m$) by setting $\beta \to \infty$, which in turn makes the Wilson loop lightlike. We also use the jet quenching as an order parameter to probe the strongly coupled domain of the dual field theory. Finally, we compute the imaginary part of the $q\overline{q}$ potential [$\mathrm{Im}(V_{q\overline{q}})$] by considering the thermal fluctuation (arbitrary long wavelength) of the string world sheet. It is observed that for fixed values of the chemical potential and rapidity, an increase in the nonconformality parameter leads to an increase in the real and imaginary potentials as well as the jet quenching parameter.

We propose a mechanism that generates a naturally light dark energy field (with Hubble-scale mass), starting from a theory with exclusively high-scale (Planckian) couplings. It is derived from the clockwork model, with $\mathcal{O}(100)$ scalar fields interacting among themselves, as well as with a 4-form field strength. We explicitly embed the key features of our model in type IIA supergravity. We also give an alternative interpretation in a braneworld setup.

The gravitational wave, traveling a long cosmological distance to reach interferometers, interacts with the (homogeneous and isotropic) cosmological background, so, generally speaking, its amplitude and phase are modified in some nontrivial way. As the sensitivity of interferometers is improved, one may detect corrections to the short-wavelength approximation, which naturally includes the information of cosmological evolution. In this work, the Newman-Penrose variable ${\mathrm{\Psi }}_4$ has been calculated to show that there are two new corrections to the short-wavelength approximation. One formally occurs at the first post-Newtonian order but is highly suppressed by the Hubble parameters; the other occurs at the fifth post-Newtonian order, which is due to the variation of the amplitude. The first correction contains the evolution of the Universe, but it may not be easily detected. The second one indicates that the short-wavelength approximation has to be corrected, when the more accurate waveforms with the higher-order post-Newtonian terms are calculated.