We obtain nonperturbative results on the sine-Gordon model using the lattice field technique. In particular, we employ the Fourier accelerated hybrid Monte Carlo algorithm for our studies. We find the critical temperature of the theory based on autocorrelation time, as well as the finite size scaling of the “thickness” observable used in an earlier lattice study by Hasenbusch et al. We study the entropy, which is smooth across all temperatures, supportive of an infinite order transition. This system has a well-known duality with the massive Thirring model, which can play the role of a toy model for Montonen-Olive duality in $\mathcal{N}=4$ super-Yang Mills theory, since it relates solitons to elementary field excitations. Our research lays a groundwork for such study on the lattice.

We present new results on up to sixth-order cumulants of net baryon-number fluctuations at small values of the baryon chemical potential, ${\mu }_B$, obtained in lattice QCD calculations with physical values of light and strange quark masses. Representing the Taylor expansions of higher-order cumulants in terms of the ratio of the two lowest-order cumulants, $M_B/{\sigma }_B^2={\chi }_1^B(T,{\mu }_B)/{\chi }_2^B(T,{\mu }_B)$, allows for a parameter-free comparison with data on net proton-number cumulants obtained by the STAR Collaboration in the Beam Energy Scan at RHIC. We show that recent high-statistics data on skewness and kurtosis ratios of net proton-number distributions, obtained at a beam energy $\sqrt{s_{NN}}=54.4\mathrm{GeV}$, agree well with lattice QCD results on cumulants of net baryon-number fluctuations close to the pseudocritical temperature, $T_{pc}({\mu }_B)$, for the chiral transition in QCD. We also present first results from a next-to-leading-order expansion of fifth- and sixth-order cumulants on the line of the pseudocritical temperatures.

We report results of numerical relativity simulations for 26 new nonspinning binary neutron star systems with 6 grid resolutions using an adaptive mesh refinement numerical relativity code sacra-mpi. The finest grid spacing is $\approx 64–85\mathrm{m}$, depending on the systems. First, we derive long-term high-precision inspiral gravitational waveforms and show that the accumulated gravitational-wave phase error due to the finite grid resolution is less than 0.5 rad during more than 200 rad phase evolution irrespective of the systems. We also find that the gravitational-wave phase error for a binary system with a tabulated equation of state (EOS) is comparable to that for a piecewise polytropic EOS. Then we validate the SACRA inspiral gravitational waveform template, which will be used to extract tidal deformability from gravitational wave observation, and find that accuracy of our waveform modeling is $\lesssim 0.1\mathrm{rad}$ in the gravitational-wave phase and $\lesssim 20\%$ in the gravitational-wave amplitude up to the gravitational-wave frequency 1000 Hz. Finally, we calibrate the proposed universal relations between a postmerger gravitational wave signal and tidal deformability/neutron star radius in the literature and show that they suffer from systematics and many relations proposed as universal are not very universal. Improved fitting formulas are also proposed.

Recently, Li and Bambi proposed a hypothesis that the event horizon of a regular black hole can be destroyed because these objects have no gravitational singularity and therefore they are not protected by the weak cosmic censorship conjecture (WCCC). In this paper, to test their hypothesis, we perform the new version of the gedanken experiments proposed by Sorce and Wald to overcharge a near extremal static electrically regular black hole. After introducing the stability condition of the spacetime and the null energy condition of matter fields, we derive the first-order and second-order perturbation inequalities of the perturbation matter fields based on the Iyer-Wald formalism. As a result, we find that these regular black holes cannot be destroyed under the second-order approximation after these two perturbation inequalities are taken into account, even though they are not protected by the WCCC. Our results indicate that there might be some deeper mechanisms to protect the event horizon of the black holes.

Considering corrections produced by modified dispersion relations on the equation of state parameter of radiation, we study the induced black hole metric inspired by Kiselev’s ansatz, thus defining a deformed Reissner-Nordström metric. In particular, we consider thermodynamic properties of such a black hole from the combined viewpoints of the modified equation of state parameter and the phenomenological approach to the quantum gravity problem called rainbow gravity.

We perform the canonical analysis of the Holst action for general relativity with a cosmological constant without introducing second-class constraints. Our approach consists in identifying the dynamical and nondynamical parts of the involved variables from the very outset. After integrating out the nondynamical variables associated with the connection, we obtain the description of phase space in terms of manifestly $SO(3,1)$ [or $SO(4)$, depending on the signature] covariant canonical variables and first-class constraints only. We impose the time gauge on them and show that the Ashtekar-Barbero formulation of general relativity emerges. Later, we discuss a family of canonical transformations that allows us to construct new $SO(3,1)$ [or $SO(4)$] covariant canonical variables for the phase space of the theory and compare them with the ones already reported in the literature, pointing out the presence of a set of canonical variables not considered before. Finally, we resort to the time gauge again and find that the theory, when written in terms of the new canonical variables, either collapses to the $SO(3)$ ADM formalism or to the Ashtekar-Barbero formalism with a rescaled Immirzi parameter.

We present the results from a search for gravitational-wave transients associated with core-collapse supernovae observed within a source distance of approximately 20 Mpc during the first and second observing runs of Advanced LIGO and Advanced Virgo. No significant gravitational-wave candidate was detected. We report the detection efficiencies as a function of the distance for waveforms derived from multidimensional numerical simulations and phenomenological extreme emission models. The sources with neutrino-driven explosions are detectable at the distances approaching 5 kpc, and for magnetorotationally driven explosions the distances are up to 54 kpc. However, waveforms for extreme emission models are detectable up to 28 Mpc. For the first time, the gravitational-wave data enabled us to exclude part of the parameter spaces of two extreme emission models with confidence up to 83%, limited by coincident data coverage. Besides, using ad hoc harmonic signals windowed with Gaussian envelopes, we constrained the gravitational-wave energy emitted during core collapse at the levels of $4.27\times {10}^{-4}{M}_{\odot }{c}^2$ and $1.28\times {10}^{-1}{M}_{\odot }{c}^2$ for emissions at 235 and 1304 Hz, respectively. These constraints are 2 orders of magnitude more stringent than previously derived in the corresponding analysis using initial LIGO, initial Virgo, and GEO 600 data.

The symmetron field is one of the promising candidates of dark energy scalar fields. In all viable candidate field theories, a screening mechanism is implemented to be consistent with existing tests of general relativity. The screening effect in the symmetron theory manifests its influence only to the thin outer layer of a bulk object, where inside a dense material the symmetry of the field is restored and no force exists. For pointlike particles such as atoms, the depth of screening is larger than the size of the particle, such that the screening mechanism is ineffective and the symmetron force is fully expressed on the atomic test particles. Extra force measurements using atom interferometry are thus much more sensitive than bulk mass based measurements, and indeed have placed the most stringent constraints on the parameters characterizing symmetron field in certain region. There is however no clear direct connection between the laboratory measurements and astrophysical observations, where the constraints are far separated by 10 orders of magnitude in the parameter space. In this paper, we present a closed-form expression for the symmetron acceleration of realistic atomic experiments. The expression is validated through numerical simulations for a terrestrial fifth-force experiment using atom interferometry. As a result, we show the connection of the atomic measurement constraints to the astrophysical ones. We also estimate the attainable symmetron constraints from a previously proposed experiment in space intended for a test of chameleon theory. The atomic constraints on the symmetron theory will be further improved by orders of magnitude.

Finite size effects come into play during the late stages of neutron star binary inspiral, with the tidal deformability of the supranuclear density matter leaving an imprint on the gravitational-wave signal. As demonstrated in the case of GW170817, this leads to a constraint on the neutron star radius (and hence the equation of state). A deeper understanding of the tidal response requires an analysis of both the state and composition of matter. While these aspects may not have dramatic impact, they could lead to systematic effects that need to be kept in mind as the observational data become more precise. As a step in this direction we explore the role of the composition of matter, which is likely to remain “frozen” during the late stages of binary inspiral. We provide the first in-depth analysis of the problem, including estimates of how composition impacts on the effective tidal deformability. The results provide improved insight into how aspects of physics that tend to be ignored impact on binary neutron star gravitational-wave signals.

We present an explicit expression for a particular $n$-gluon two-loop scattering partial amplitude. Specifically we present an analytic form for the single-trace $N_c$-independent color partial amplitude for the case where all external gluons have positive helicity.

The continuously improving sensitivity of dark matter direct detection experiments has limited the interaction between dark matter and nucleons being increasingly feeble, while the dark matter relic density favors it to take part in weak interactions. After taking into account the constraints from the Large Hadron Collider (LHC) search for Higgs bosons and sparticles, it is becoming difficult for the neutralino dark matter in the minimal Supersymmetric Standard Model and the next-to-minimal supersymmetric Standard Model to possess these two seemingly paradoxical features in their most natural parameter space for electroweak symmetry breaking due to the limited theoretical structure. In contrast, the seesaw extension of the next-to-minimal supersymmetric Standard Model, which was initially proposed to solve the neutrino mass problem, enables the lightest sneutrino to act as a viable dark matter candidate, readily has these features, and thus, it easily satisfies the constraints from dark matter and LHC experiments. Compared with the Type-I seesaw extension, the dark matter physics in the inverse seesaw extension is more flexible, allowing it to be consistent with the experimental results in broader parameter space. We conclude that weakly interacting massive particles (such as the sneutrino in this study) work well in supersymmetric theories as dark matter candidates.

Ultraviolet completions for axionlike particles (ALPs) lighter than the neutral pion generically induce ALP-neutral pion mixing and are therefore sensitive to direct constraints on the mixing angle. For ALPs below the pion mass, we demonstrate that strong and novel bounds on the ALP-pion mixing angle can be extracted from existing rare pion decay data, measured by the PIENU and PIBETA experiments.

In this work we introduce $CPT$-odd nonminimal Lorentz-symmetry violating couplings to the electroweak sector modifying the interaction between leptons and gauge bosons. The vertex rules allow us to calculate tree-level processes modified by the presence of the novel dimension-five operators. For definitiveness, we investigate the $W$ decay into a lepton-neutrino pair, the $Z$ decay into pairs of charged and neutral leptons, as well as the decay of the muon. By comparing the experimental measurements on these processes to our results we are able to bound several combinations of the background 4-vectors to be $\lesssim {10}^{-4}{\mathrm{GeV}}^{-1}$.

Motivated by the fermion-bag approach, we construct a new class of Hamiltonian lattice field theories that can help us to study fermionic quantum critical points, particularly those with four-fermion interactions. Although these theories are constructed in discrete time with a finite temporal lattice spacing $ϵ$, when $ϵ\to 0$, conventional continuous-time Hamiltonian lattice field theories are recovered. The fermion-bag algorithms run relatively faster when $ϵ=1$ as compared to $ϵ\to 0$ but still allow us to compute universal quantities near the quantum critical point even at such a large value of $ϵ$. As an example of this new approach, here we study the $N_f=1$ Gross-Neveu chiral-Ising universality class in $2+1$ dimensions by calculating the critical scaling of the staggered mass order parameter. We show that we are able to study lattice sizes up to ${100}^2$ sites when $ϵ=1$, while with comparable resources we can reach lattice sizes of only up to ${64}^2$ when $ϵ\to 0$. The critical exponents obtained in both these studies match within errors.

We study $J/\psi$ and ${\eta }_c$ inclusive production in $\mathrm{\Upsilon }$ decay within the framework of nonrelativistic-QCD (NRQCD) factorization. In the latter case, for which no experimental data exist so far, we also include the $h_c$ feed-down contribution. We calculate the short-distance coefficients completely through $\mathcal{O}({\alpha }_s^5)$. The NRQCD predictions for the branching fraction $\mathcal{B}(\mathrm{\Upsilon }\to J/\psi +X)$ via direct production, evaluated with different sets of long-distance matrix elements (LDMEs), all agree with the experimental data in a reasonable range of renormalization scale. Using ${\eta }_c$ and $h_c$ LDMEs obtained from $J/\psi$ and ${\chi }_c$ ones via heavy-quark spin symmetry, we find that the bulk of $\mathcal{B}(\mathrm{\Upsilon }\to {\eta }_c+X)$ via prompt production arises from the $c\overline{c}({{}^{3}S}_1^{[8]})$ Fock state. The experimental study of this decay process would, therefore, provide a particularly clean probe of the color octet mechanism of heavy-quarkonium production.

The finite size effect on hadron physics and quark matter has attracted much interest for more than three decades; normally, both the periodic (with a zero-momentum mode) and the antiperiodic (without a zero-momentum mode) spatial boundary condition are applied for fermions. By comparing the thermodynamical potential, it is found that, if there is no other physical constraint, the droplet quark matter is always more stable when the periodic spatial boundary condition is applied, and the catalysis of chiral symmetry breaking is observed with the decrease of the system size, while the pions excited from the droplet vacuum remain as pseudo–Nambu-Goldstone bosons. Furthermore, it is found that the zero-momentum-mode contribution brings a significant change of the chiral apparent phase transition in a droplet of cold dense quark matter: The first-order chiral apparent phase transition becomes quantized; i.e., the first-order apparent phase transition is completed in two steps, which is a brand-new quantum phenomenon. It is expected that the catalysis of chiral symmetry breaking and the quantized first-order phase transition are common features for fermionic systems with a quantized momentum spectrum with a zero-mode contribution, which also shows up in quark matter under a magnetic field.

We describe a method of construction of gauge-invariant operators (Dirac observables or “evolving constants of motion”) from the knowledge of the eigenstates of the gauge generator in time-reparametrization invariant mechanical systems. These invariant operators evolve unitarily with respect to an arbitrarily chosen time variable. We emphasize that the dynamics is relational, both in the classical and quantum theories. In this framework, we show how the “emergent Wentzel-Kramers-Brillouin time” often employed in quantum cosmology arises from a weak-coupling expansion of invariant transition amplitudes, and we illustrate an example of singularity avoidance in a vacuum Bianchi I (Kasner) model.

In this paper, we construct an effective rotating loop quantum black hole (LQBH) solution, starting from the spherical symmetric LQBH by applying the Newman-Janis algorithm modified by Azreg-Aïnou’s noncomplexification procedure, and study the effects of loop quantum gravity (LQG) on its shadow. Given the rotating LQBH, we discuss its horizon, ergosurface, and regularity as $r\to 0$. Depending on the values of the specific angular momentum $a$ and the polymeric function $P$ arising from LQG, we find that the rotating solution we obtained can represent a regular black hole, a regular extreme black hole, or a regular spacetime without horizon (a non-black-hole solution). We also study the effects of LQG and rotation, and show that, in addition to the specific angular momentum, the polymeric function also causes deformations in the size and shape of the black hole shadow. Interestingly, for a given value of $a$ and inclination angle ${\theta }_0$, the apparent size of the shadow monotonically decreases, and the shadow gets more distorted with increasing $P$. We also consider the effects of $P$ on the deviations from the circularity of the shadow, and find that the deviation from circularity increases with increasing $P$ for fixed values of $a$ and ${\theta }_0$. Additionally, we explore the observational implications of $P$ in comparing with the latest Event Horizon Telescope observation of the supermassive black hole, M87*. The connection between the shadow radius and quasinormal modes in the eikonal limit as well as the deflection of massive particles are also considered.

In this work, we study two-dimensional Galilean field theories with global translations and anisotropic scaling symmetries. We show that such theories have enhanced local symmetries, generated by the infinite dimensional spin-$\ell$ Galilean algebra with possible central extensions, under the assumption that the dilation operator is diagonalizable and has a discrete and non-negative spectrum. We study the Newton-Cartan geometry with anisotropic scaling, on which the field theories could be defined in a covariant way. With the well-defined Newton-Cartan geometry we establish the state-operator correspondence in anisotropic Galilean conformal field theory and determine the two-point functions of primary operators.

Multiple scalar fields nonminimally interacting through pure affine gravity are considered to generate primordial perturbations during an inflationary phase. The couplings considered give rise to two distinct sources of entropy perturbations that may not be suppressed in the long wavelength limit. The first is merely induced by the presence of more than one scalar and arises even in the minimal coupling limit. The second source, however, is restricted to nonminimal interaction. Unlike the case of metric gravity, and due to the absence of anisotropic stresses, the second source disappears for a single scalar, showing that nonminimal couplings become relevant to nonadiabatic perturbations only when more than one scalar field are considered. Hence the notion of adiabaticity is not affected by the transition to minimal coupling contrary to the metric gravity case where it is confused by changing the frames. Precise data that might be able to neatly track different sources of isocurvature modes, if any, must not only distinguish between different models of inflation but also determine the most viable approach to gravity that underlies the inflationary dynamics itself.