We describe both the Fermi velocity and the mass renormalization due to the two-dimensional Coulomb interaction in the presence of a thermal bath. To achieve this, we consider an anisotropic version of pseudoquantum electrodynamics, within a perturbative approach in the fine-structure constant $\alpha$. Thereafter, we use the so-called imaginary-time formalism for including the thermal bath. In the limit $T\to 0$, we calculate the renormalized mass $m^R(\mathrm{p})$ and compare this result with the experimental findings for the energy band gap in monolayers of transition metal dichalcogenides, namely, ${\mathrm{WSe}}_2$ and ${\mathrm{MoS}}_2$. In these materials, the quasiparticle excitations behave as massive Dirac-like particles in the low-energy limit, hence, its mass is related to the energy band gap of the material. In the low-temperature limit $T\ll v_F\mathrm{p}$, where $v_F\mathrm{p}$ is taken as the Fermi energy, we show that $m^R(\mathrm{p})$ decreases linearly on the temperature, i.e., $m^R(\mathrm{p},T)-m^R(\mathrm{p},T\to 0)\approx -A_{\alpha }T+O(T^3)$, where $A_{\alpha }$ is a positive constant. On the other hand, for the renormalized Fermi velocity, we find that $v_F^R(\mathrm{p},T)-v_F^R(\mathrm{p},T\to 0)\approx -B_{\alpha }{T}^3+O(T^5)$, where $B_{\alpha }$ is a positive constant. We also perform numerical tests which confirm our analytical results.

Effect of spatially oscillating field on Schwinger pair production is studied numerically and analytically when the work done by the electric field over its spatial extent is smaller than twice the electron mass. Under large spatial scale, we explain the characteristics of the position and momentum distribution of created pairs via the tunneling picture for the Dirac vacuum. Moreover, the exact Dirac-Heisenberg-Wigner formalism can be simplified by some alternative methods such as local density approximation, analytical approximation, and locally constant field approximation when the spatial scale is large in a certain of spatial oscillating cycle number. Also, the validity of these alternative methods are illustrated and discussed. For the studied spatially oscillating field, our results show that the maximum reduced particle number is about 5 times in comparison with the maximum one of nonoscillating inhomogeneous field.

A cosmic first-order phase transition occurring at the MeV scale provides an attractive explanation for the nano-Hertz gravitational wave (GW) background, which is indicated by the recent pulsar timing array data from the NANOGrav, CPTA, EPTA, and PPTA Collaborations. We propose this explanation can be further tested at the colliders if the hidden sector couples to the Standard Model sector via the Higgs portal. Through a careful analysis of the thermal history in the hidden sector, we demonstrate that in order to explain the observed GW signal, the portal coupling must be sizable so that it can be probed through Higgs invisible decay at the LHC or future lepton colliders such as CEPC, ILC, and FCC-ee. Our research offers a promising avenue to uncover the physical origin of the nano-Hertz GWs through particle physics experiments.

The renormalizable extension of a pure Yang-Mills theory with Lorentz violation is characterized by the $CPT$-Even $(k_F{)}_{\mu \nu \lambda \rho }$ and the $CPT$-Odd $(k_{AF}{)}_{\mu }$ constant Lorentz coefficients. In this paper, the one-loop structure of the theory up to second order in these Lorentz violating coefficients is studied using the background field method gauge. Results for the diverse beta functions are derived and contrasted with those given in the literature at first order in these parameters. Special emphasis is put on the beta function $\beta (g)$, which is studied in both mass-independent and mass-dependent renormalization schemes. It is found that in a mass-independent scheme the $(k_{AF}{)}_{\mu }$ Lorentz coefficient does not contribute to the $\beta (g)$ function, but it does in a mass-dependent scheme with contributions that are gauge dependent and IR divergent.

It is likely that the Higgs potential of the Standard Model is unstable, turning negative at $\varphi <\mathrm{\Lambda }\sim {10}^{10}\mathrm{GeV}$. Here we consider whether it is possible to have Higgs inflation on the positive stable region of the potential at $\varphi <\mathrm{\Lambda }$. To do this we add a nonminimally coupled induced gravity sector with scalar $\chi$ to the Standard Model. For an appropriate form for the nonminimal coupling of $\chi$, we show that it is possible to have conventional Higgs inflation at small $\varphi <\mathrm{\Lambda }$ if the effective Planck mass in the Jordan frame during inflation is sufficiently small, with a phase transition to $\chi \ne 0$ at the end of Higgs inflation which increases the Jordan frame Planck mass to its presently observed value. In the Einstein frame this corresponds to a suppression of the Higgs kinetic and potential term at the end of inflation. We show that the predictions of Higgs inflation at tree level are unaltered from conventional Higgs inflation, with the exception of the magnitude of the Higgs field during inflation. Hence, Higgs inflation can be achieved using the potential of the unmodified Standard Model.

It has been shown in [S. Steinhaus and J. Thürigen, Phys. Rev. D 98, 026013 (2018)] that a class of restricted spin foam models can feature a reduced spectral dimension of space-time. However, it is still an open question how curvature affects the flow of the spectral dimension. To answer this question, we consider another class of restricted spin foam models, so-called spin foam frusta, which naturally exhibit oscillating amplitudes induced by curvature, as well as an extension of the parameter space by a cosmological constant. Numerically computing the spectral dimension of one-periodic frusta geometries using extrapolated quantum amplitudes, we find that quantum effects lead to a small change of spectral dimension at small scales and an agreement to semiclassical results at larger scales. Adding a cosmological constant $\mathrm{\Lambda }$, we find additive corrections to the nonoscillating result at the diffusion scale $\tau \sim 1/\sqrt{\mathrm{\Lambda }}$. Extending to two-periodic configurations, we observe a reduced effective dimension, the form of which sensitively depends on the values of the gravitational constant $G$ and the cosmological constant $\mathrm{\Lambda }$. We provide an intuition for our results based on an analytical estimate of the spectral dimension. Furthermore, we present a simplified integrable model with oscillating measure that qualitatively explains the features found numerically. We argue that there exists a phase transition in the thermodynamic limit which crucially depends on the parameters $G$ and $\mathrm{\Lambda }$. In principle, the dependence on $G$ and $\mathrm{\Lambda }$ presents an exciting opportunity to infer phenomenological insights about quantum geometry from measurement of the spectral dimension.

We study the magnetic field effects on the quantum critical point (QCP) in the holographic Weyl semimetal model. We show that it increases quadratically with the magnetic field for weak field and linearly with the magnetic field for strong field. Our findings are compatible with previous results in the literature from other approaches.

We show how to formulate celestial twistor amplitudes in Yang-Mills (YM) and gravity. This is motivated by a refined holographic correspondence between the twistor transform and the light transform in the boundary Lorentzian CFT. The resulting amplitudes are then equivalent to light transformed correlators on the celestial torus. Using an ambidextrous basis of twistor and dual twistor variables, we derive formulas for the three- and four-point YM and gravity amplitudes. The four-point amplitudes take a particularly simple form in terms of elementary functions, with a striking correspondence between the YM and gravity expressions. We derive celestial twistor Britto–Cachazo–Feng–Witten recursion relations and show how these may be used to generate the four-point YM amplitude, illuminating the structure it inherits from the three-point amplitude and paving the way for the calculation of higher multiplicity light transformed correlators. Throughout our calculations we utilize the unique properties of the boundary structure of split signature, and in order to properly motivate and highlight these properties, we first develop our methodology in Lorentzian signature. This also allows us to prove a holographic correspondence between Fourier transforms in Lorentzian signature and shadow transforms in the Euclidean boundary CFT.

We study quantum field theories with boundaries by utilizing noninvertible symmetries. We consider three kinds of boundary conditions of the four dimensional ${\mathbb{Z}}_2$ lattice gauge theory at the critical point as examples. The weights of the elements on the boundary are determined so that these boundary conditions are related by the Kramers-Wannier-Wegner (KWW) duality. In other words, it is required that the KWW duality defects ending on the boundary are topological. Moreover, we obtain the ratios of the hemisphere partition functions with these boundary conditions; this result constrains the boundary renormalization group flows.

Results on the isolation of the radiative degrees of freedom of the gravitational field with a positive cosmological constant in full general relativity are put forward. Methods employed in a recent geometric characterization of gravitational radiation are used and, inspired by Ashtekar’s work on asymptotically flat space-times, a space of connections is defined. Ground differences emerge due to the spacelike character of the conformal boundary, and one has to put into play a fundamental result by Friedrich concerning the initial value problem for space-times with a positive cosmological constant. Based on this, half of the radiative degrees of freedom are identified; remarkably, they utterly determine the gravitational radiation content for space-times with algebraically special rescaled Weyl tensor at infinity. Directions for defining the phase space in the general case are proposed.

Numerical relativity simulations provide the most precise templates for the gravitational waves produced by binary black hole mergers. However, many of these simulations use an incomplete waveform extraction technique—extrapolation—that fails to capture important physics, such as gravitational memory effects. Cauchy-characteristic evolution (CCE), by contrast, is a much more physically accurate extraction procedure that fully evolves Einstein’s equations to future null infinity and accurately captures the expected physics. In this work, we present a new surrogate model, NRHybSur3dq8_CCE, built from CCE waveforms that have been mapped to the post-Newtonian (PN) BMS frame and then hybridized with PN and effective one-body (EOB) waveforms. This model is trained on 102 waveforms with mass ratios $q\le 8$ and aligned spins ${\chi }_{1z},{\chi }_{2z}\in [-0.8,0.8]$. The model spans the entire LIGO-Virgo-KAGRA (LVK) frequency band (with $f_{\mathrm{low}}=20\mathrm{Hz}$) for total masses $M\gtrsim 2.25M_{\odot }$ and includes the $\ell \le 4$ and $(\ell ,m)=(5,5)$ spin-weight $-2$ spherical harmonic modes, but not the (3, 1), (4, 2) or (4, 1) modes. We find that NRHybSur3dq8_CCE can accurately reproduce the training waveforms with mismatches $\lesssim 2\times {10}^{-4}$ for total masses $2.25M_{\odot }\le M\le 300M_{\odot }$ and can, for a modest degree of extrapolation, capably model outside of its training region. Most importantly, unlike previous waveform models, the new surrogate model successfully captures memory effects.

Future long-baseline experiments will play an important role in exploring physics beyond the standard model. One such new physics concept is the large extra dimension (LED), which provides an elegant solution to the hierarchy problem. This model also explains the small neutrino mass in a natural way. The presence of the LED modifies the standard neutrino oscillation probabilities. Hence, the long-baseline experiments are sensitive to the LED parameters. We explore the potential of the three future long-baseline neutrino experiments, namely, T2HK, ESSnuSB, and DUNE, to probe the LED parameter space. We also compare the capability of the charged and neutral current measurements at DUNE to constrain the LED model. We find that T2HK will provide more stringent bounds on the largest compactification radius ($R_{\mathrm{ED}}$) compared to the DUNE and ESSnuSB experiments. At 90% confidence limits, T2HK can exclude $R_{\mathrm{ED}}\sim 0.45(0.425)\mathrm{\mu }\mathrm{m}$ for the normal (inverted) mass hierarchy scenario.

The hot, neutron-rich, and dense circumstance in core-collapse supernovae provides a source of negatively charged pions that may make up a significant portion of the matter. These abundant thermal pions offer an opportunity to populate light and hidden hypothetical particles. In this study, we discuss the dark gauge boson production via reactions involving supernova pions. The rate of this production is determined by the isovector nucleon coupling. We consider two toy models, the dark photon and the gauged $B-L$ models, that carry the typical distinct isovector nucleon coupling structure in the medium. Pion-induced dark gauge bosons leave an imprint on several observational consequences associated with supernova. Their sizable emissivity and characteristic hard spectral distribution result in the stringent constraints on the dark gauge boson models, in particular at masses above the two electron mass.

To understand the true origin of flowlike signatures and applicability of hydrodynamics in small collision systems, effects of soft QCD dynamics, the sensitivity of jetlike correlations, and nonequilibrium effects, efforts are being made to perform $p$-O and O-O collisions at the LHC and RHIC energies. It is equally interesting to look into the possible signatures of an $\alpha$-clustered nuclear geometry in ${}^{16}\mathrm{O}\text{−}{}^{16}\mathrm{O}$ collisions by studying the initial-state effects on the final-state observables. In this work, within a multiphase transport model, we implement an $\alpha$-cluster tetrahedral density profile in the oxygen nucleus along with the default Woods-Saxon density profile. We study the eccentricity (${\epsilon }_2$), triangularity (${\epsilon }_3$), normalized symmetric cumulants [NSC(2,3)], elliptic flow ($v_2$), and triangular flow ($v_3$) in ${}^{16}\mathrm{O}\text{−}{}^{16}\mathrm{O}$ collisions at $\sqrt{s_{\mathrm{NN}}}=7\mathrm{TeV}$. The constituent quark number scaling of the elliptic flow is also reported. For the most central collisions, enhanced effects in $⟨{\epsilon }_3⟩/⟨{\epsilon }_2⟩$ and $⟨v_3⟩/⟨v_2⟩$ with a negative value of NSC(2,3), and an away-side broadening in the two-particle azimuthal correlation function [$C(\mathrm{\Delta }\varphi )$] of the identified particles are observed in the presence of an $\alpha$-clustered geometry.

We carry out the first calculation for the twist-3 gluon contribution to the single transverse-spin asymmetry (SSA) in $J/\psi$ production in semi-inclusive deep inelastic scattering. Our result shows that the $J/\psi$ SSA is an ideal observable to pin down the $C$-even type twist-3 gluon distribution that has a direct relationship with the gluon transverse-momentum-dependent distribution function. We also perform some numerical simulations of the $J/\psi$ SSA for the kinematics accessible at the future electron-ion-collider experiment. For color-singlet contribution, the hadronization effect of $J/\psi$ is completely canceled at the level of the SSA, and the spin-dependent structure functions directly reflect the behavior of the $C$-even twist-3 gluon distribution.

We provide a reinterpretation of the quantum vacuum ambiguities that one encounters when studying particle creation phenomena due to an external and time-dependent agent. We propose a measurement-motivated understanding: Each way of measuring the number of created particles selects a particular vacuum. This point of view gives a clear and physical meaning to the time evolution of the number of particles produced by the agent as the counts in a specific detector and, at the same time, relates commonly used quantization prescriptions to particular measurement setups.

The double-copy program relies crucially on the so-called color-kinematics duality which, in turn, is widely believed to descend from a kinematic algebra possessed by gauge theories. In this paper we construct the kinematic algebra of gauge-invariant and off shell self-dual Yang-Mills theory, up to trilinear maps. This structure is a homotopy algebra of the same type as the ones recently uncovered in Chern-Simons and full Yang-Mills theories. To make contact with known results for the self-dual sector, we show that it reduces to the algebra found by Monteiro and O’Connell upon taking the light cone gauge and partially solving the self-duality constraints. Finally, we test a double-copy prescription recently proposed in Bonezzi et al. [Gauge invariant double copy of Yang-Mills theory: The quartic theory, Phys. Rev. D 107, 126015 (2023)] and reproduce self-dual gravity.

The uniqueness problem of static axially symmetric black hole in a magnetic universe filled with dark matter component is considered in this paper. The dark matter model comprises of the additional $U(1)$ gauge field (dark photon) interacting with the Maxwell one through the kinetic mixing term. We show that all the solutions of Einstein-Maxwell dark photon gravity subject to the same boundary and regularity conditions authorize the only static axially symmetric black hole solutions with nonvanishing time and azimuthal components of Maxwell and hidden-sector gauge fields, e.g., Schwarzschild-like black hole immersed in a dark matter Melvin universe.

Over the last few years, there has been an increasing interest in sub-solar-mass black holes due to their potential to provide valuable information about cosmology or the black hole population. Motivated by this, we study observable phenomena connected to the merger of a sub-solar-mass black hole with a neutron star. For this purpose, we perform new numerical-relativity simulations of a binary system composed of a black hole with mass $0.5M_{\odot }$ and a neutron star with mass $1.4M_{\odot }$. We investigate the merger dynamics of this exotic system and provide information about the connected gravitational-wave and kilonova signals. Our study indicates that current gravitational-waveform models cannot adequately describe such systems and that phenomenological relations connecting the binary parameters with the ejecta and remnant properties do not apply to our system. Furthermore, we find a dependence of the kilonova signal on the azimuthal viewing angle due to the asymmetric mass ejection. This first-of-its-kind simulation opens the door for studying sub-solar-mass black hole–neutron star mergers and could serve as a testing ground for future model development.