A new sufficient condition for photons emitted near future null infinity to reach future null infinity is derived by studying null geodesics in the Bondi coordinates in asymptotically flat spacetimes. In our previous works [M. Amo et al., Phys. Rev. D 104, 064025 (2021).; M. Amo et al., Phys. Rev. D 105, 064074 (2022).], such a condition was established for photons emitted in outward or tangential directions to constant radial surfaces. This paper improves our previous result by including photons emitted in inward directions. In four dimensions, imposing the same assumptions on the metric functions as previously, we prove that photons reach future null infinity if their initial values of $|dr/du|$ are smaller than a certain quantity, where $r$ and $u$ are the radial and retarded time coordinates, respectively. This quantity is determined by the asymptotic properties of the metric and is connected to the conjectured maximal luminosity. In higher dimensions, photons emitted with $dr/du>-(1-1/\sqrt{3})\approx -0.423$ are shown to reach future null infinity without the assumptions on the metric functions.

Increasing attention has recently focused on nontraditional dark-matter production mechanisms which result in primordial dark-matter velocity distributions with highly nonthermal shapes. In this paper, we undertake an assessment of how the detailed shape of a general dark-matter velocity distribution impacts structure formation in the nonlinear regime. In particular, we investigate the impact on the halo-mass and subhalo-mass functions, as well as on astrophysical observables such as satellite and cluster-number counts. We find that many of the standard expectations no longer hold in situations in which this velocity distribution takes a highly nontrivial, even multimodal shape. For example, we find that the nominal free-streaming scale alone becomes insufficient to characterize the effect of free-streaming on structure formation. In addition, we propose a simple one-line conjecture which can be used to “reconstruct” the primordial dark-matter velocity distribution directly from the shape of the halo-mass function. Although our conjecture is completely heuristic, we show that it successfully reproduces the salient features of the underlying dark-matter velocity distribution even for nontrivial distributions which are highly nonthermal and/or multimodal, such as might occur for nonminimal dark sectors. Moreover, since our approach relies only on the halo-mass function, our conjecture provides a method of probing dark-matter properties even for scenarios in which the dark and visible sectors interact only gravitationally.

The kilo-Hertz gravitational waves radiated by the neutron star merger remnants carry rich information about the physics of high-density nuclear matter states, and many important astrophysical phenomena such as gamma-ray bursts and black hole formation. Current laser interferometer gravitational wave detectors, such as LIGO, VIRGO, and KAGRA have limited signal response at the kilo-Hertz band, thereby being unable to capture these important physical phenomena. This work proposes an alternative protocol for boosting the sensitivity of the gravitational wave detectors at high frequency by implementing an optomechanical quantum amplifier. With the auxiliary quantum amplifier, this design has the feature of parity-time ($PT$) symmetry so that the detection band will be significantly broadened within the kilo-Hertz range. In this work, we carefully analyze the quantum-noise-limited sensitivity and the dynamical stability of this design. Based on our protocol, our result shows that the quantum-noise-limited sensitivity will be improved by one order of magnitude around 3 kHz, which indicates the potential of our design for a future search of neutron star merger signals.

We investigate the effects of relative motion on entanglement harvesting by considering a pair of Unruh-Dewitt detectors moving at arbitrary but independent and constant velocities, both linearly interacting with a massless scalar field vacuum in four-dimensional Minkowski spacetime. Working within the weak coupling approximation, we find that the negativity is a (nonelementary) function of the relative velocity of the detectors, as well as their energy gaps and minimal separation. We find parameter regions where negativity increases with velocity up to a maximum and then decreases, reaching zero at some sublight velocity. At any given relative velocity, the harvested entanglement is inversely correlated with the detector energy gap (at sufficiently high values) and the distance of closest approach of two detectors.

We investigated the strange hadrons transverse momentum ($p_T$) spectra in Au-Au collision at $\sqrt{s_{NN}}=54.4\mathrm{GeV}$ in the framework of modified Hagedorn function with embedded flow. It is found that the model can describe the particle spectra well. We extracted the kinetic freeze-out temperature $T_0$, transverse flow velocity ${\beta }_T$, kinetic freeze-out volume $V$, mean transverse momentum $⟨p_T⟩$, the entropy parameter $n$, and the multiplicity parameter $N_0$. We reported that all these parameters increase towards the central collisions. The larger kinetic freeze-out temperature, transverse flow velocity, kinetic freeze-out volume, and the entropy parameter ($n$) in central collisions compared to peripheral collisions show the early decoupling of the particles in central collisions. In addition, all the above parameters are mass dependent. The kinetic freeze-out temperature ($T_0$), the entropy parameter $n$, and mean transverse momentum ($⟨p_T⟩$) are larger for massive particles, while the transverse flow velocity (${\beta }_T$), kinetic freeze-out volume ($V$), and the multiplicity parameter ($N_0$) show the opposite behavior. Larger $T_0$, $n$, and smaller ${\beta }_T$ as well as $V$ of the heavier particles indicate the early freeze-out of the heavier particles, while larger $⟨p_T⟩$ for the heavier particles evince that the effect of radial flow is stronger in heavier particles. The separate set of parameters for each particle shows the multiple kinetic freeze-out scenario, where the mass-dependent kinetic freeze-out volume shows the volume differential freeze-out scenario. We also checked the correlation among different parameters, which include the correlation of $T_0$ and ${\beta }_T$, $T_0$ and $V$, ${\beta }_T$ and $V$, $⟨p_T⟩$ and $T_0$, $⟨p_T⟩$ and ${\beta }_T$, $⟨p_T⟩$, and $V$, $n$ and $T_0$, $n$ and ${\beta }_T$, and $n$ and $V$, and they all are observed to have positive correlations with each other which validates our results.

Gas-rich dwarf galaxies located outside the virial radius of their host are relatively pristine systems and have ultralow gas cooling rates. This makes them very sensitive to heat injection by annihilation or decay of dark matter (DM). Such dwarfs are particularly sensitive to DM producing $e^{\pm }$ with energies 1–100 MeV or photons with energies 13.6 eV–1 keV, because these products can be efficiently thermalized in the neutral hydrogen gas of the dwarfs. Following the methodology of Wadekar and Farrar [Phys. Rev. D 103, 123028 (2021)], we require the rate of heat injection by DM to not exceed the ultralow radiative cooling rate of gas in the Leo T dwarf galaxy. This gives model-independent bounds on (i) the decay lifetime of DM to $e^{\pm }$ (photons), which are stronger than all the previous literature for $m_{\mathrm{DM}}\sim 1–10\mathrm{MeV}$ ($m_{\mathrm{DM}}\sim 0.02–1\mathrm{keV}$), (ii) annihilation of DM to $e^{\pm }$ comparable to constraints from cosmic microwave background and $\mathrm{x}/\gamma$-ray surveys. We also translate our bounds for the case of the following DM models: axionlike particles (ALPs), sterile neutrinos, excited DM states, Higgs portal scalars, and dark baryons. Observations of gas-rich low-mass dwarfs from upcoming 21 cm and optical surveys can therefore be powerful probes of a multitude of models of DM.

We consider the generation of the baryon asymmetry in models with right-handed neutrinos produced through gravitational scattering of the inflaton during reheating. The right-handed neutrinos later decay and generate a lepton asymmetry, which is partially converted to a baryon asymmetry by Standard Model sphaleron processes. We find that a sufficient asymmetry can be generated for a wide range of right-handed neutrino masses and reheating temperatures. We also show that the same type of gravitational scattering produces Standard Model Higgs bosons, which can achieve inflationary reheating consistent with the production of a baryon asymmetry.

We propose a minimal model based on lepton number symmetry (and violation), to address a common origin of baryon asymmetry, dark matter and neutrino mass generation. The model consists of a vectorlike fermion to constitute the dark sector, three right-handed neutrinos (RHNs) to dictate leptogenesis and neutrino mass, while an additional complex scalar is assumed to be present in the early Universe the decay of which produces both dark matter and RHNs via lepton number violating and lepton number conserving interactions respectively. Interestingly, the presence of the same scalar helps in making the electroweak vacuum stable until the Planck scale. The unnatural largeness and smallness of the parameters required to describe correct experimental limits are attributed to lepton number violation. The allowed parameter space of the model is illustrated via a numerical scan.

We perform hybrid Monte-Carlo simulation of lattice QCD with $N_f=2+1+1$ domain-wall quarks at the physical point, on the ${64}^3\times (64,20,16,12,10,8,6)$ lattices, each with three lattice spacings. The lattice spacings and the bare quark masses are determined on the ${64}^4$ lattices. The resulting gauge ensembles provide a basis for studying finite temperature QCD with $N_f=2+1+1$ domain-wall quarks at the physical point. In this paper, we determine the topological susceptibility of the QCD vacuum for $T>T_c\sim 150\mathrm{MeV}$. The topological charge of each gauge configuration is measured by the clover charge in the Wilson flow at the same flow time in physical units, and the topological susceptibility ${\chi }_t(a,T)$ is determined for each ensemble with lattice spacing $a$ and temperature $T$. Using the topological susceptibility ${\chi }_t(a,T)$ of 15 gauge ensembles with three lattice spacings and different temperatures in the range $T\sim 155–516\mathrm{MeV}$, we extract the topological susceptibility ${\chi }_t(T)$ in the continuum limit. To compare our results with others, we survey the continuum extrapolated ${\chi }_t(T)$ in lattice QCD with $N_f=2+1(+1)$ dynamical quarks at/near the physical point and discuss their discrepancies. Moreover, a detailed discussion on the reweighting method for the domain-wall fermion is presented.

A novel method of formulating the twist-3 gluon fragmentation function contribution to hyperon polarization in the proton-proton collision is presented. The method employs a covariant gauge and takes full advantage of the Ward-Takahashi identities before performing the collinear expansion. It provides a robust way of constructing the general cross section formula and also a clear understanding for the absence of the ghostlike terms in the twist-3 cross section in the leading order with respect to the QCD coupling constant.

We evaluate the longitudinal or (chromo-)electric Yang-Mills gluon propagator in the recently proposed center-symmetric Landau gauge at finite temperature [D. M. van Egmond et al., SciPost Phys. 12, 087 (2022).]. To model the effect of the Gribov copies in the infrared, we use the Curci-Ferrari model which, in turn, allows us to rely on perturbative calculations. At one-loop order in the SU(2) case, the so-obtained longitudinal gluon propagator provides a clear signature for $Z_2$ center-symmetry breaking with a singular behavior, characteristic of a continuous phase transition. This is in sharp contrast with what is found within the standard Landau gauge. We also identify various signatures for $Z_3$ center-symmetry breaking in the SU(3) case in the form of genuine order parameters. Among those, we find that the gluon propagator, although degenerate along the diagonal color directions in the confining phase, becomes nondegenerate in the deconfined phase. Our results open new ways of identifying the transition from correlation functions both within continuum approaches and on the lattice.

In global analyses of nuclear parton distribution functions (nPDFs), neutrino deep-inelastic scattering (DIS) data have been argued to exhibit tensions with the data from charged-lepton DIS. Using the nCTEQ framework, we investigate these possible tensions both internally and with the datasets used in our recent nPDF analysis nCTEQ15WZSIH. We take into account nuclear effects in the calculation of the deuteron structure function $F_2^D$ using the CJ15 analysis. The resulting nPDF fit, nCTEQ15WZSIHdeut, serves as the basis for our comparison with inclusive neutrino DIS and charm dimuon production data. Using ${\chi }^2$ hypothesis testing, we confirm evidence of tensions with these data and study the impact of the proton PDF baseline as well as the treatment of data correlation and normalization uncertainties. We identify the experimental data and kinematic regions that generate the tensions and present several possible approaches how a consistent global analysis with neutrino data can be performed. We show that the tension can be relieved using a kinematic cut at low $x$ ($x>0.1$) and also investigate a possibility of managing the tensions by using uncorrelated systematic errors. Finally, we present a different approach identifying a subset of neutrino data which leads to a consistent global analysis without any additional cuts. Understanding these tensions between the neutrino and charged-lepton DIS data is important not only for a better flavor separation in global analyses of nuclear and proton PDFs, but also for neutrino physics and for searches for physics beyond the Standard Model.

We present the implementation and validation of the Hartree-Fock continuum random phase approximation (HF-CRPA) model in the GENIE neutrino-nucleus interaction event generator and a comparison of the subsequent predictions to experimental measurements of lepton kinematics from interactions with no mesons in the final state. These predictions are also compared to those of other models available in GENIE. It is shown that, with respect to these models, HF-CRPA predicts a significantly different evolution of the cross section when moving between different interaction targets, when considering incoming antineutrinos compared to neutrinos and when changing neutrino energies. These differences are most apparent for interactions with low-energy and momentum transfer. It is also clear that the impact of nucleon correlations within the HF-CRPA framework is very different than in GENIE’s standard implementation of RPA corrections. Since many neutrino oscillation experiments rely on their input model to extrapolate between targets, flavors, and neutrino energies, the newly implemented HF-CRPA model provides a useful means to verify that such differences between models are appropriately covered in oscillation analysis systematic error budgets.

Most matter in the Universe is invisible and unknown, and is called dark matter. A candidate of dark matter is the axion, which is an ultralight particle motivated as a solution for the $CP$ problem. Axions form clouds in a galactic halo, and amplify and delay a part of gravitational waves propagating in the clouds. The Milky Way is surrounded by the dark matter halo composed of a number of axion patches. Thus, the characteristic secondary gravitational waves are always expected right after the reported gravitational-wave signals from compact binary mergers. In this paper, we derive a realistic amplitude of the secondary gravitational waves. Then we search the gravitational waves having the characteristic time delay and duration with a method optimized for them. We find no significant signal. Assuming the axions are a dominant component of dark matter, we obtain the constraints on the axion coupling to the parity-violating sector of gravity for the mass range, $[1.7\times {10}^{-13},8.5\times {10}^{-12}]\mathrm{eV}$, which is at most $\sim 10$ times stronger than that from Gravity Probe B.

The branching ratio of the $K^{+}\to {\pi }^{+}{e}^{+}{e}^{-}{e}^{+}{e}^{-}$ ($K^{+}\to {\pi }^{+}4e$) decay is calculated at leading order in the Standard Model. The dominance of the neutral-pion pole determines the overall branching ratio to be $B(K^{+}\to {\pi }^{+}4e)=B(K^{+}\to {\pi }^{+}{\pi }^0)B({\pi }^0\to 4e)\approx 7.0(3)\times {10}^{-6}$. The significance of this contribution is very much concentrated in the context of the whole available phase space, throughout most of which the one-photon-exchange topology is prevalent in turn. It is thus interesting to present branching ratios for only parts of the allowed kinematical region. We find, for instance, $B(K^{+}\to {\pi }^{+}4e,m_{4e}>150\mathrm{MeV})=6.0(6)\times {10}^{-11}$.

The diffractive photoproduction of $J/\mathrm{\Psi }$ on a nucleon is mostly due to gluonic exchanges at all $\sqrt{s}$. In holographic QCD (large number of colors and strong ${}^{\prime }\mathrm{t}$ Hooft coupling), these exchanges are captured by gravitons near threshold, and their reggeized form (Pomeron) asymptotically. We revisit our holographic analysis of the $A$ and $D$ gravitational form factors in light of the new lattice data, and use them to refine our predictions for the photoproduction of $J/\mathrm{\Psi }$ near threshold, and the comparison to the GlueX data. We use these results to estimate the scalar and mass radii of the nucleon, and describe the gravitational pressure and shear across a nucleon.

It was recently pointed out that linear quantum fields $\widehat{\varphi }(x)$ can be meaningfully propagated across the big bang (and the big crunch) singularities of spatially flat Friedmann, Lemaître, Robertson, Walker (FLRW) universes [A. Ashtekar et al., Adv. Theor. Math. Phys. 25, 1651 (2021)]. Recall that $\widehat{\varphi }(x)$, as well as renormalized observables $⟨{\widehat{\varphi }}^2(x){⟩}_{\mathrm{ren}}$ and $⟨{\widehat{T}}_{ab}(x){⟩}_{\mathrm{ren}}$, are distribution valued already in Minkowskian quantum field theories. It was shown that they can be extended as well-defined distributions even when these spacetimes are enlarged to include the big bang (or the big crunch). We generalize these results to spatially closed and open FLRW models, showing that this “tameness” of cosmological singularities is not an artifact of the technical simplifications due to spatial flatness. Our analysis also provides explicit expressions of $⟨\widehat{\varphi }(x)\widehat{\varphi }(x^{\prime })⟩,⟨{\widehat{\varphi }}^2(x){⟩}_{\mathrm{ren}}$ and $⟨{\widehat{T}}_{ab}(x){⟩}_{\mathrm{ren}}$ in closed and open universes for minimally coupled massless scalar fields and discuss the ambiguities in the definition of $⟨{\widehat{T}}_{ab}(x){⟩}_{\mathrm{ren}}$ at the big bang. While the technical expressions are more complicated than in the spatially flat case, there is also an unexpected conceptual simplification: the infrared divergence [L. H. Ford and L. Parker, Phys. Rev. D 16, 245 (1977)] is now absent because, in effect, the spatial curvature provides a natural cutoff. Finally, we further clarify the sense in which quantum field theory can continue to be well defined even though the extended spacetime is not globally hyperbolic because of the singularity, and suggest directions for further work.

The ($2+1$)-dimensional generalized massless Thirring model with four-component Fermi fields is investigated by the Hartree-Fock method. The Lagrangian of this model is constructed from two different four-fermion structures. One of them takes into account the vector $\times$ vector channel of fermion interaction with coupling constant $G_v$, the other, the scalar $\times$ scalar channel with coupling $G_s$. At some relation between bare couplings $G_s$ and $G_v$, the Hartree-Fock equation for self-energy of fermions can be renormalized, and dynamical generation of the Dirac and Haldane fermion masses is possible. As a result, a phase portrait of the model consists of two nontrivial phases. In the first one the chiral symmetry is spontaneously broken due to dynamical appearance of the Dirac mass term, while in the second phase a spontaneous breaking of the spatial parity $\mathcal{P}$ is induced by a Haldane mass term. It is shown that in the particular case of a pure Thirring model, i.e., at $G_s=0$, the ground state of the system is indeed a mixture of these phases. Moreover, it was found that dynamical generation of fermion masses is possible for any finite number of Fermi fields.

We consider a braneworld scenario in the simplest setting, $M_4\times S^1$, with a four-dimensional (4D) Minkowski metric induced on the brane, and establish the possibility of superluminal propagation. If the brane is at rest, the 4D Lorentz symmetry of the brane is exact, but if the brane is in motion, it is broken globally by the compactification. By measuring bulk fields, an observer on the brane sees a slice through a higher-dimensional field profile, which carries an imprint of the extra dimensions even when the brane is at rest. If the brane is in motion, we find that bulk fields can propagate outside the brane light cone by a parametrically large amount set by the brane velocity. We mention observational tests and possible applications to cosmology.

All existing treatments of bimetric MOND (modified Newtonian dynamics) (BIMOND)—a class of relativistic versions of MOND—have dealt with a rather restricted subclass: The Lagrangian of the interaction between the gravitational degrees of freedom—the two metrics—is a function of a certain single scalar argument built from the difference in connections of the two metrics. I show that the scope of BIMOND is much richer: The two metrics can couple through several scalars to give theories that all have a “good” nonrelativistic (NR) limit—one that accounts correctly, à la MOND, for the dynamics of galactic systems, including gravitational lensing. This extended-BIMOND framework exhibits a qualitative departure from the way we think of MOND at present, as encapsulated, in all its aspects, by one “interpolating function” of one acceleration variable. After deriving the general field equations, I pinpoint the subclass of theories that satisfy the pivotal requirement of a good NR limit. These involve three independent, quadratic scalar variables. In the NR limit these scalars all reduce to the same acceleration scalar, and the NR theory then does hinge on one function of a single acceleration variable—representing the NR MOND interpolating function, whose form is largely dictated by the observed NR galactic dynamics. However, these scalars take different values and behave differently in different relativistic contexts. So, the full richness of the multivariable Lagrangian, as it enters cosmology, for example, or gravitational-wave dynamics, is hardly informed by what we learn of MOND from observations of galactic dynamics. In this paper, I present the formalism, with some generic examples. I also consider some cosmological solutions where the two metrics are small departures from one Friedmann-Lemaitre-Robertson-Walker metric. This may offer a framework for describing cosmology within the extended BIMOND.