In this paper we calculate the scalar induced gravitational waves (SIGWs) accompanying the formation of primordial black holes during the radiation dominated era in three different gauges, i.e., the synchronous gauge, Newton gauge, and uniform curvature gauge, and we find that the energy density spectra of SIGWs, ${\mathrm{\Omega }}_{\mathrm{GW}}(k)$, are identical in these three different gauges.

We conduct force-free simulations of a single neutron star undergoing orbital motion in flat spacetime, mimicking the trajectory of the star about the center of mass on a compact binary system. Our attention is focused on the kinetic energy being extracted from the orbit by the acceleration of the magnetic dipole moment of the neutron star and, particularly, on how this energy gets distributed within its surrounding magnetosphere. A detailed study of the resulting magnetospheric configurations in our setting is presented, incorporating as well the effects due to neutron star spin and the misalignment of the magnetic and orbital axes. We find many features resembling those of pulsar magnetospheres for the orbiting neutron star—even in the absence of spin-of particular interest being the development of a spiral current sheet that extends beyond the light cylinder. Then, we use recent advances in pulsar theory to estimate electromagnetic emissions produced at the reconnection regions of such current sheets.

Dark matter (DM) can consist of very light bosons behaving as a classical scalar field that experiences coherent oscillations. The presence of this DM field would perturb the dynamics of celestial bodies, either because the (oscillating) DM stress tensor modifies the gravitational potentials of the galaxy or if DM is directly coupled to the constituents of the body. We study secular variations of the orbital parameters of binary systems induced by such perturbations. Two classes of effects are identified. Effects of the first class appear if the frequency of DM oscillations is in resonance with the orbital motion; these exist for general DM couplings including the case of purely gravitational interaction. Effects of the second class arise if DM is coupled quadratically to the masses of the binary system members and do not require any resonant condition. The exquisite precision of binary pulsar timing can be used to constrain these effects. Current observations are not sensitive to oscillations in the galactic gravitational field, though a discovery of pulsars in regions of high DM density may improve the situation. For DM with direct coupling to ordinary matter, the current timing data are already competitive with other existing constraints in the range of DM masses $\sim {10}^{-22}-{10}^{-18}\mathrm{eV}$. Future observations are expected to increase the sensitivity and probe new regions of parameters.

We study the end point of the first-order deconfinement phase transition in two- and $2+1$-flavor QCD in the heavy quark region of the quark mass parameter space. We determine the location of the critical point at which the first-order deconfinement phase transition changes to a crossover, and calculate the pseudoscalar meson mass at the critical point. Performing quenched QCD simulations on lattices with the temporal extents $N_t=6$ and 8, the effects of heavy quarks are determined using the reweighting method. We adopt the hopping parameter expansion to evaluate the quark determinants in the reweighting factor. We estimate the truncation error of the hopping parameter expansion by comparing the results of leading- and next-to-leading-order calculations, and study the lattice spacing dependence as well as the spatial volume dependence of the result for the critical point. The overlap problem of the reweighting method is also examined. Our results for $N_t=4$ and 6 suggest that the critical quark mass decreases as the lattice spacing decreases and increases as the spatial volume increases.

We study isospin-1 $P$-wave $\pi \pi$ scattering in lattice QCD with two flavors of $\mathrm{O}(a)$ improved Wilson fermions. For pion masses ranging from $m_{\pi }=265\mathrm{MeV}$ to $m_{\pi }=437\mathrm{MeV}$, we determine the energy spectrum in the center-of-mass frame and in three moving frames. We obtain the scattering phase shifts using Lüscher’s finite-volume quantization condition. Fitting the dependence of the phase shifts on the scattering momentum to a Breit-Wigner form allows us to determine the corresponding $\rho$ mass $m_{\rho }$ and $g_{\rho \pi \pi }$ coupling. By combining the scattering phase shifts with the decay matrix element of the vector current, we calculate the timelike pion form factor, $F_{\pi }$, and compare the results to the Gounaris-Sakurai representation of the form factor in terms of the resonance parameters. In addition, we fit our data for the form factor to the functional form suggested by the Omnès representation, which allows for the extraction of the charge radius of the pion. As a further application, we discuss the long-distance behavior of the vector correlator, which is dominated by the two-pion channel. We reconstruct the long-distance part in two ways: one based on the finite-volume energies and matrix elements, and the other based on $F_{\pi }$. It is shown that this part can be accurately constrained using the reconstructions, which has important consequences for lattice calculations of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment.

Khuri-Treiman equations have proven to be a useful theoretical tool in the analysis of three-body decays, especially into the $3\pi$ final state. In this work we present in full detail the necessary generalization of the formalism to study the decays of particles with arbitrary spin, parity, and charge conjugation. To this extent, we find it most convenient to work with helicity amplitudes instead of the so-called invariant amplitudes, especially when dealing with the unitarity relations. The isobar expansions in the three possible ($s$-, $t$-, and $u$-) final channels are related with the appropriate crossing matrices. We pay special attention to the kinematical singularities and constraints of the helicity amplitudes, showing that these can be derived by means of the crossing matrix.

The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section, mean transverse momentum, mean transverse momentum squared of inclusive $J/\psi$, and cross section ratio of $\psi (2S)$ to $J/\psi$ at forward rapidity in $p+p$ collisions at $\sqrt{s}=510\mathrm{GeV}$ via the dimuon decay channel. Comparison is made to inclusive $J/\psi$ cross sections measured at $\sqrt{s}=200\mathrm{GeV}$ and 2.76–13 TeV. The result is also compared to leading-order nonrelativistic QCD calculations coupled to a color-glass-condensate description of the low-$x$ gluons in the proton at low transverse momentum ($p_T$) and to next-to-leading order nonrelativistic QCD calculations for the rest of the $p_T$ range. These calculations overestimate the data at low $p_T$. While consistent with the data within uncertainties above $\approx 3\mathrm{GeV}/c$, the calculations are systematically below the data. The total cross section times the branching ratio is BR $d{\sigma }_{pp}^{J/\psi }/dy(1.2<|y|<2.2,0<p_T<10\mathrm{GeV}/c)=54.3\pm 0.5(\mathrm{stat})\pm 5.5(\mathrm{syst})\mathrm{nb}$.

We consider a class of correlation measures for quantum states called optimized correlation measures defined as a minimization of a linear combination of von Neumann entropies over purifications of a given state. Examples include the entanglement of purification $E_P$ and squashed entanglement $E_{\mathrm{sq}}$. We show that when evaluating such measures on “nice" holographic states in the large-$N$ limit, the optimal purification has a semiclassical geometric dual. We then apply this result to confirm several holographic dual proposals, including the $n$-party squashed entanglement. Moreover, our result suggests two new techniques for determining holographic duals: holographic entropy inequalities and direct optimization of the dual geometry.

In any consistent massive quantum field theory there are well-known bounds on scattering amplitudes at high energies. In conformal field theory there is no scattering amplitude, but the Mellin amplitude is a well-defined object analogous to the scattering amplitude. We prove bounds at high energies on Mellin amplitudes in conformal field theories, valid under certain technical assumptions. Such bounds are derived by demanding the absence of spurious singularities in position space correlators. We also conjecture a stronger bound, based on evidence from several explicit examples.

Following the idea of Alekseev and Shatashvili, we derive the path integral quantization of a modified relativistic particle action that results in the Feynman propagator of a free field with arbitrary spin. This propagator can be associated with the Duffin, Kemmer, and Petiau (DKP) form of a free field theory. We show explicitly that the obtained DKP propagator is equivalent to the standard one, for spins 0 and 1. We argue that this equivalence holds also for higher spins.

The Einstein-Hilbert Lagrangian has no well-defined variational derivative with respect to the metric. This issue has to be tackled by adding a suitable surface term to the action, which is a peculiar feature of gravity. We also know that null surfaces in spacetime exhibit (observer-dependent) thermodynamic features. This suggests a possible thermodynamic interpretation of the boundary term when the boundary is a null surface. For timelike/spacelike surfaces it is easy to construct the boundary term but there are some subtleties in the case of the null surface. The correct form of boundary term for null surfaces was obtained recently from first principles. We show that this surface term, as well as its variation, has direct thermodynamic interpretation in terms of a heat density of null surfaces. The implications of the result are discussed.

Displacement and velocity memory effects in the exact, vacuum, plane gravitational wave line element have been studied recently by looking at the behavior of pairs of geodesics or via geodesic deviation. Instead, one may investigate the evolution of geodesic congruences. In our work here, we obtain the evolution of the kinematic variables which characterize timelike geodesic congruences, using chosen pulse profiles (square and sech squared) in the exact, plane gravitational wave line element. We also analyze the behavior of geodesic congruences in possible physical scenarios describable using derivatives (first, second and third) of one of the chosen pulses. Beginning with a discussion on the generic behavior of such congruences and consequences thereof, we find exact analytical expressions for shear and expansion with the two chosen pulse profiles. Qualitatively similar numerical results are noted when various derivatives of the sech-squared pulse are used. We conclude that for geodesic congruences, a growth (or decay) of shear causes focusing of an initially parallel congruence, after the departure of the pulse. A correlation between the “focusing time” (or $u$ value, $u$ being the affine parameter) and the amplitude of the pulse (or its derivatives) is found. Such features distinctly suggest a memory effect, named in recent literature as $\mathcal{B}$ memory.

We introduce the concept of inflationary twin models, that is, a class of generalized (kinetic or “K inflation”) field theories which lead exactly to the same cosmological evolution during the inflationary period as a given standard scalar field theory of inflation. The twin concept permits us to introduce generalized, K-inflation theories in a controlled manner, maintaining some inflationary predictions unaltered. Further, this concept allows us to extend analytical tools like the slow-roll expansion to the realm of K-inflation theories, facilitating their investigation. Twins of a standard scalar field model of inflation still may result in different results for some inflationary observables, because of their nontrivial scalar speed of sound. This implies that nonstandard twins may lead to completely viable models of inflation, even if their standard twin is ruled out by observations. We provide some explicit examples of this possibility, including the physical case of a dilaton–Dirac-Born-Infeld theory.

In this work, we investigate cosmologies where the gravitational constant varies in time, with the aim of explaining the accelerated expansion without a cosmological constant. We achieve this by considering a phenomenological extension to general relativity, modifying Einstein’s field equations such that $G$ is a function of time, $G(t)$, and we preserve the geometrical consistency (Bianchi identity) together with the usual conservation of energy by introducing a new tensor field to the equations. In order to have concrete expressions to compare with cosmological data, we posit additional properties to this tensor field, in a way that it can be interpreted as a response of spacetime to a variation of $G$. Namely, we require that the energy this tensor represents is nonzero only when there is a time variation of $G$, and its energy depends on the scale factor only because of its coupling to $G$ and the matter and radiation energy densities. Focusing on the accelerated expansion period, we use type Ia supernovae and baryon acoustic oscillation data to determine the best fit of the cosmological parameters as well as the required variation in the gravitational constant. As a result, we find that it is possible to explain the accelerated expansion of the Universe with a variation of $G$ and no cosmological constant. The obtained variation of $G$ stays under 10% of its current value in the investigated redshift range, and it is consistent with the local observations of $\dot{G}/G$.

We reanalyze data collected with the DarkSide-50 experiment and recently used to set limits on the spin-independent interaction rate of weakly interacting massive particles (WIMPs) on argon nuclei with an effective field theory framework. The dataset corresponds to a total $(16660\pm 270)\mathrm{kg}\mathrm{d}$ exposure using a target of low-radioactivity argon extracted from underground sources. We obtain upper limits on the effective couplings of the 12 leading operators in the nonrelativistic systematic expansion. For each effective coupling we set constraints on WIMP-nucleon cross sections, setting upper limits between $2.4\times {10}^{-45}{\mathrm{cm}}^2$ and $2.3\times {10}^{-42}{\mathrm{cm}}^2$ ($8.9\times {10}^{-45}{\mathrm{cm}}^2$ and $6.0\times {10}^{-42}{\mathrm{cm}}^2$) for WIMPs of mass of $100\mathrm{GeV}/{\mathrm{c}}^2$ ($1000\mathrm{GeV}/{\mathrm{c}}^2$) at 90% confidence level.

Charge-parity-time ($CPT$) symmetry governs that the oscillation parameters for neutrinos and antineutrinos are to be identical. Different mass and mixing parameters for these particles may give us a possible hint for $CPT$ violation in the neutrino sector. Using this approach, we discuss the ability of long-baseline and atmospheric neutrino experiments to determine the difference between mass squared splittings ($\mathrm{\Delta }{m}_{32}^2-\mathrm{\Delta }{\overline{m}}_{32}^2$) and atmospheric mixing angles (${\sin }^2{\theta }_{23}-{\sin }^2{\overline{\theta }}_{23}$) of neutrinos and antineutrinos. We show the joint sensitivity of the T2K, NOvA, and INO experiments to such $CPT$ violating observables in different possible combinations of octant for neutrinos and antineutrinos.

We perform a systematic study on the twist-3 gluon distribution and fragmentation functions which appear in the collinear twist-3 factorization for hard inclusive processes. Three types of twist-3 distribution and fragmentation functions, i.e., intrinsic, kinematical, and dynamical ones, which are necessary to describe all kinds of twist-3 cross sections, are related to each other by the operator identities based on the QCD equation of motion and the Lorentz invariance properties of the correlation functions. We derive the exact relations for all twist-3 gluonic distribution and fragmentation functions for a spin-$1/2$ hadron. Those relations allow one to express intrinsic and kinematical twist-3 gluon functions in terms of the twist-2 and dynamical twist-3 functions, which provides a basis for the renormalization of intrinsic and kinematical twist-3 functions. In addition, those model independent relations are crucial to guarantee gauge invariance and frame independence properties of the twist-3 cross sections.

The densest state of matter in the Universe is uniquely realized inside the central cores of the neutron star. While first-principles evaluation of the equation of state of such matter remains as one of the long-standing problems in nuclear theory, evaluation in light of neutron star phenomenology is feasible. Here we show results from a novel theoretical technique to utilize a deep neural network with supervised learning. We input up-to-date observational data from neutron star x-ray radiations into the trained neural network and estimate a relation between the pressure and the mass density. Our results are consistent with extrapolation from the conventional nuclear models and the experimental bound on the tidal deformability inferred from gravitational wave observation.

We present results for the charged kaon-box contributions to the hadronic light-by-light (HLBL) correction of the muon’s anomalous magnetic moment. To this end we determine the kaon electromagnetic form factor within the functional approach to QCD using Dyson-Schwinger and Bethe-Salpeter equations and evaluate the kaon-box contribution as defined in the dispersive approach to HLBL. As an update to previous work we also reevaluate the charged pion-box contribution taking effects due to isospin breaking into account. Our results are $a_{\mu }^{{\pi }^{\pm }-\mathrm{box}}=-15.7(2)(3)\times {10}^{-11}$ and $a_{\mu }^{K^{\pm }-\mathrm{box}}=-0.48(2)(4)\times {10}^{-11}$ thus confirming the large suppression of box contributions beyond the leading pion box.

Pion valence, glue, and sea distributions are calculated using a continuum approach to the two valence-body bound-state problem. Since the framework is symmetry preserving, physical features of the distributions are properly expressed. The analysis reveals that the emergent phenomenon of dynamical chiral symmetry breaking causes a hardening of the valence-quark distribution function, ${\mathfrak{q}}^{\pi }(x)$. Nevertheless, this distribution exhibits the $x\simeq 1$ behavior predicted by quantum chromodynamics (QCD). At the scale ${\zeta }_2≔2\mathrm{GeV}$, the following momentum fractions are predicted: $⟨x_{\text{valence}}⟩=0.48(3)$, $⟨x_{\mathrm{glue}}⟩=0.41(2)$, $⟨x_{\mathrm{sea}}⟩=0.11(2)$. Evolving to $\zeta =5.2\mathrm{GeV}$, the result for ${\mathfrak{q}}^{\pi }(x)$ agrees with that computed using lattice QCD. These outcomes should both spur improved analyses of existing experiments and stimulate efforts to obtain new data on the pion distribution functions using available and envisioned facilities.