In this work we study static neutron stars in the context of several inflationary models which are popular in cosmology. These inflationary models are nonminimally coupled scalar theories which yield a viable inflationary phenomenology in both Jordan and Einstein frames. By considering the constraints from inflationary theories, which basically determine the values of the potential strength, usually considered as a free parameter in astrophysical neutron star works, we construct and solve the Tolman-Oppenheimer-Volkoff equations using a solid Python-3 LSODA integrator. For our study we consider several popular inflationary models, such as the universal attractors, the $R^p$ attractors (three distinct model values), the induced inflation, the quadratic inflation, the Higgs inflation and the $a$-attractors (two distinct model values) and for the following popular equations of state the WFF1, the SLy, the APR, the MS1, the AP3, the AP4, the ENG, the MPA1 and the MS1b. We construct the $M-R$ diagram and we confront the resulting theory with theoretical and observational constraints. As we demonstrate, remarkably, all the neutron stars produced by all the inflationary models we considered are compatible with all the constraints for the MPA1 equation of state. It is notable that for this particular equation of state, the maximum masses of the neutron stars are in the mass-gap region with $M>2.5M_{\odot }$, but lower than the three solar masses causal limit. Another important feature of our work is that it may be possible to discriminate inflationary attractors which at the cosmological level are indistinguishable using the $M-R$ graphs of static neutron stars, however we point out the limitations in discriminating the inflationary attractors. Also we show that the WFF1, MS1 and MS1b seem to be entirely ruled out, regarding a viable description of static neutron stars. We also make the observation that as the NICER constraints are pushed towards larger radii, as for example in the case of the black widow pulsar PSR J0952-0607, it seems that equations of state that produce neutron stars with maximum masses in the mass gap region, with $M>2.5M_{\odot }$, but lower than the three solar masses causal limit, are favored and are compatible with the modified NICER constraints. Finally we question the ability of the MPA1 equation of state to pass all the theoretical and observational constraints and we impose the question whether this equation of state plays any fundamental role in static neutron star physics.

We use updated type Ia $\mathrm{Pantheon}+\text{supernova}$, baryon acoustic oscillation, and Hubble parameter (now also accounting for correlations) data, as well as new reverberation-measured C iv quasar data, and quasar angular size, H ii starburst galaxy, reverberation-measured Mg ii quasar, and Amati-correlated gamma-ray burst data to constrain cosmological parameters. We show that these datasets result in mutually consistent constraints and jointly use them to constrain cosmological parameters in six different spatially flat and nonflat cosmological models. Our analysis provides summary model-independent determinations of two key cosmological parameters: the Hubble constant, $H_0=69.8\pm 1.3\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$, and the current nonrelativistic matter density parameter, ${\mathrm{\Omega }}_{m0}=0.288\pm 0.017$. Our summary error bars are 2.4 and 2.3 times those obtained using the flat cosmological constant cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) model and Planck $\mathrm{TT},\mathrm{TE},\mathrm{EE}+\mathrm{lowE}+\text{lensing}$ cosmic microwave background (CMB) anisotropy data. Our $H_0$ value is very consistent with that from the local expansion rate based on the tip of the red giant branch and type Ia supernova (SN Ia) data, is $2\sigma$ lower than that from the local expansion rate based on Cepheid and SN Ia data, and is $2\sigma$ higher than that in the flat $\mathrm{\Lambda }\mathrm{CDM}$ model based on Planck $\mathrm{TT},\mathrm{TE},\mathrm{EE}+\mathrm{lowE}+\text{lensing}$ CMB data. Our data compilation shows at most mild evidence for nonflat spatial hypersurfaces, but more significant evidence for dark energy dynamics, $2\sigma$ or larger in the spatially flat dynamical dark energy models we study.

We study a simple complex scalar singlet dark matter (DM) model with $Z_3$ symmetry in the framework of the type-II seesaw mechanism. We use the model to explain the excess of electron-positron flux measured by the AMS-02, DAMPE, and Fermi-LAT Collaborations, which is encouraged by the decay of the triplets produced from dark matter annihilations in the Galactic halo. We focus on the nondegenerate case in which the mass of DM is larger than that of the triplets’ and deliberately alleviates the leptophilic properties of the DM, so that the semiannihilation effects are enhanced. With the guarantee of $Z_3$ symmetry, by fitting the antiproton spectrum observed in the PAMELA and AMS experiments, we find that the DM cubic terms and the couplings between DM and the Higgs boson are strongly constrained, leading to the semiannihilation cross-section fraction less than 11% when DM mass is given at 2 TeV.

New physics in the rare top decays $t\to q{\ell }^{+}{\ell }^{-}$ is currently very weakly constrained. We show that in a large class of Standard Model extensions, existing experimental constraints on new physics in flavor-conserving processes imply strong indirect bounds on new physics contributions to flavor-violating processes of the form $t\to q{\ell }^{+}{\ell }^{-}$. These indirect bounds arise from basic principles of quantum field theory together with a few generic conditions on the UV structure of the theory, and are roughly an order of magnitude stronger than the present experimental bounds on the same processes. These constraints provide a theoretically motivated target for experimental searches for $t\to q{\ell }^{+}{\ell }^{-}$: violation of these bounds would exclude a large class of new physics models, and would provide nontrivial insight into the UV behavior of the new physics.

The low-energy spectrum and scattering of two-nucleon systems are studied with lattice quantum chromodynamics using a variational approach. A wide range of interpolating operators are used: dibaryon operators built from products of plane-wave nucleons, hexaquark operators built from six localized quarks, and quasilocal operators inspired by two-nucleon bound-state wave functions in low-energy effective theories. Sparsening techniques are used to compute the timeslice-to-all quark propagators required to form correlation-function matrices using products of these operators. Projection of these matrices onto irreducible representations of the cubic group, including spin-orbit coupling, is detailed. Variational methods are applied to constrain the low-energy spectra of two-nucleon systems in a single finite volume with quark masses corresponding to a pion mass of 806 MeV. Results for $S$- and $D$-wave phase shifts in the isospin singlet and triplet channels are obtained under the assumption that partial-wave mixing is negligible. Tests of interpolating-operator dependence are used to investigate the reliability of the energy spectra obtained and highlight both the strengths and weaknesses of variational methods. These studies and comparisons to previous studies using the same gauge-field ensemble demonstrate that interpolating-operator dependence can lead to significant effects on the two-nucleon energy spectra obtained using both variational and nonvariational methods, including missing energy levels and other discrepancies. While this study is inconclusive regarding the presence of two-nucleon bound states at this quark mass, it provides robust upper bounds on two-nucleon energy levels that can be improved in future calculations using additional interpolating operators and is therefore a step toward reliable nuclear spectroscopy from the underlying Standard Model of particle physics.

Boost-invariant equations of spin hydrodynamics confined to the first-order terms in gradients are numerically solved. The spin equation of state, relating the spin density tensor to the spin chemical potential, is consistently included in the first order. Depending on its form and the structure of the spin transport coefficients, we find solutions which are both stable and unstable within the considered evolution times of $10\mathrm{fm}/\mathrm{c}$. These findings are complementary to the recent identification of stable and unstable modes for perturbed uniform spin systems described by similar hydrodynamic frameworks.

The detection of black-hole binaries at high redshifts is a cornerstone of the science case of third-generation gravitational-wave interferometers. The star-formation rate peaks at $z\sim 2$ and decreases by orders of magnitude by $z\sim 10$. Any confident detection of gravitational waves from such high redshifts would imply either the presence of stars formed from pristine material originating from cosmological nucleosynthesis (the so-called population III stars), or black holes that are the direct relics of quantum fluctuations in the early Universe (the so-called primordial black holes). Crucially, detecting sources at cosmological distances does not imply inferring that sources are located there, with the latter posing more stringent requirements. To this end, we present two figures of merit, which we refer to as “$z\text{−}z$ plot” and “inference horizon,” that quantify the largest redshift one can possibly claim a source to be beyond. We argue that such inference requirements, in addition to detection requirements, should be investigated when quantifying the scientific payoff of future gravitational-wave facilities.

We discuss all-order transseries in one of the simplest quantum mechanical systems: a U(1) symmetric single-degree-of-freedom system with a first-order time derivative term. Following the procedure of the Lefschetz thimble method, we explicitly evaluate the path integral for the generating function of the Noether charge and derive its exact transseries expression. Using the conservation law, we find all the complex saddle points of the action, which are responsible for the nonperturbative effects and the resurgence structure of the model. The all-order power-series contributions around each saddle point are generated from the one-loop determinant with the help of the differential equations obeyed by the generating function. The transseries are constructed by summing up the contributions from all the relevant saddle points, which we identify by determining the intersection numbers between the dual thimbles and the original path integration contour. We confirm that the Borel ambiguities of the perturbation series are canceled by the nonperturbative ambiguities originating from the discontinuous jumps of the intersection numbers. The transseries computed in the path-integral formalism agrees with the exact generating function, whose explicit form can be obtained in the operator formalism thanks to the integrable nature of the model. This agreement indicates the nonperturbative completeness of the transseries obtained by the semiclassical expansion of the path integral based on the Lefschetz thimble method.

We study the homoclinic orbit and the violation of chaos bound, which are obtained by particle motions around a black hole that coexist with anisotropic matter fields. The homoclinic one is associated with an unstable local maximum of the effective potential. By perturbing a particle located slightly away from the homoclinic one, we numerically compute Lyapunov exponents indicating the sensitivity of the initial value. Our results demonstrate that the violation of the chaos bound increases with higher angular momentum, and the anisotropic matter gives rise to violating the chaos bound further, even in the case of the nonextremal black hole. We utilize the Hamiltonian-Jacobi formalism to explicitly illustrate how the geodesic motion of a particle can be integrable in the procedure of obtaining our findings.

Recent measurements of the primordial ${}^4\mathrm{He}$ abundance $Y_p$ from EMPRESS suggest a cosmological scenario with an effective number of neutrino species that deviates from the standard value and a nonzero lepton asymmetry. We argue that the standard cosmological model would be extended further if the Hubble tension were taken into account, in which the derived baryon density could be somewhat higher than the in the standard $\mathrm{\Lambda }\mathrm{CDM}$ framework. We also discuss the issue by assuming early dark energy whose energy density can have a sizable fraction at the epoch of big bang nucleosynthesis. We show that the existence of early dark energy can reduce some of the tension implied by the EMPRESS $Y_p$ results.

Recent pulsar timing array experiments have reported a hint of gravitational stochastic background in nHz band frequency. Further confirmation might rely on whether the signature of the signals is consistent with that sketched by overlap reduction functions, known as Hellings-Downs curves. This paper investigates the nonlinear corrections of overlap reduction functions in the presence of non-Gaussianity, in which the self-interaction of gravity is first taken into account. Expanding Einstein field equations and geodesic equations into the nonlinear regime, we obtain nonlinear corrections for the timing residuals of pulsar timing, and theoretically study the overlap reduction functions for pulsar timing arrays. In the event of considerable correction from the three-point correlations of gravitational waves, the shapes of the overlap reduction functions with nonlinear corrections can be differentiated from Hellings-Downs curves.

With planned space-based and 3rd generation ground-based gravitational wave detectors (LISA, Einstein Telescope, Cosmic Explorer), and proposed DeciHz detectors (DECIGO, Big Bang Observer), it is timely to explore statistical cosmological tests that can be employed with the forthcoming plethora of data, ${10}^4–{10}^6$ mergers a year. We forecast the combination of the standard siren measurement with the weak lensing of gravitational waves from binary mergers. For 10 years of 3rd generation detector runtime, this joint analysis will constrain the dark energy equation of state with marginalized $1\sigma$ uncertainties of $\sigma (w_0)\sim 0.005$ and $\sigma (w_a)\sim 0.04$. This is comparable to or better than forecasts for future galaxy/intensity mapping surveys, and better constraints are possible when combining these and other future probes with gravitational waves. We find that combining mergers with and without an electromagnetic counterpart helps break parameter degeneracies. Using DeciHz detectors in the post-LISA era, we demonstrate for the first time how merging binaries could achieve a precision on the sum of neutrino masses of $\sigma (\mathrm{\Sigma }{m}_{\nu })\sim 0.05\mathrm{eV}$ using $3\times {10}^6$ sources up to $z=3.5$ with a distance uncertainty of 1%, and $\sim \mathrm{percent}$ or subpercent precision also on curvature, dark energy, and other parameters, independently from other probes. Finally, we demonstrate how the cosmology dependence in the redshift distribution of mergers can be exploited to improve dark energy constraints if the cosmic merger rate is known, instead of relying on measured distributions as is standard in cosmology. In the coming decades gravitational waves will become a formidable probe of both geometry and large scale structure.

Diffuse gamma-ray emission (DGE) has been discovered over the Galactic disk in the energy range from sub-GeV to sub-PeV. While it is believed to be dominated by the pionic emission of cosmic ray hadrons via interactions with interstellar medium, unresolved gamma-ray sources may also be potential contributors. TeV gamma-ray halos around middle-aged pulsars have been proposed as such sources. Their contribution to DGE, however, highly depends on the injection rate of electrons and the injection spectral shape, which are not well determined based on current observations. The measured fluxes of DGE can thus provide constraints on the $e^{\pm }$ injection of the pulsar halo population in turn. In this paper, we estimate the contribution of pulsar halos to DGE based on the Australia Telescope National Facility pulsar samples with taking into account the off-beam pulsars. The recent measurement on DGE by Tibet $\mathrm{AS}\gamma$ and an early measurement by Multiple Institution Los Alamos Gamma Ray Observatory (MILAGRO) are used to constrain the pair injection parameters of the pulsar halo population. Our result may be used to distinguish different models for pulsar halos.

We study the Large Hadron Collider (LHC) search potential of a ${\mathbb{Z}}_4$-based two Higgs doublet model which can simultaneously explain the muon $g-2$ anomaly and the observed dark matter. The neutral scalars in the second Higgs doublet couple to $\mu$ and $\tau$ and largely contribute to the muon anomalous magnetic moment through the one-loop diagram involving $\tau$ and scalars. An additional singlet scalar which is charged under the discrete symmetry can be a dark matter candidate. An upper limit on the scalar mass originates from the unitarity constraint, and the $\mu \tau$ flavor-violating nature of the scalars predicts nonstandard signatures at the LHC. However, the previously proposed ${\mu }^{\pm }{\mu }^{\pm }{\tau }^{\mp }{\tau }^{\mp }$ signal via the electroweak heavy neutral scalar pair production at the LHC loses sensitivity for increasing scalar mass. We revisit this model and investigate the LHC prospects for the single production of the $\mu \tau$ flavor-violating neutral scalar. It is shown that the single scalar process helps to extend the LHC reach to the 1 TeV mass regime of the scenario. The search potential at the high energy LHC is also discussed.

We show that a conformal extension of the standard model with local $B-L$ symmetry and two complex scalars breaking $B-L$ can provide a unified description of neutrino mass, origin of matter, and dark matter. There are two hierarchical $B-L$ breaking vacuum expectation value (VEV) scales in the model, the higher denoted by $v_B$ and the lower by $v_A$. The higher breaking scale is dynamically implemented via the Coleman-Weinberg mechanism and plays a key role in the model since it induces electroweak symmetry breaking as well as the lower $B-L$ breaking scale. It is also responsible for neutrino masses via the seesaw mechanism and origin of matter. The imaginary part of the complex scalar with lower $B-L$ breaking VEV plays the role of a pseudo-Goldstone dark matter (DM). The DM particle is unstable with its lifetime naturally longer than ${10}^{28}$ seconds. We show that its relic density arises from the freeze-in mechanism for a wide parameter domain. Due to the pseudo-Goldstone boson nature of the DM particle, the direct detection cross section is highly suppressed. The model also predicts the dark matter to be heavier than 100 TeV and it decays to two high energy neutrinos which can be observable at the IceCube, providing a test of this model.

Future gravitational wave observations are potentially sensitive to new physics corrections to the Higgs potential once the first-order electroweak phase transition arises. We study the Standard Model effective field theory (SMEFT) dimension-six operator effects on the Higgs potential, where three types of effects are taken into account: (i) SMEFT tree level effect on ${\phi }^6$ operator, (ii) SMEFT tree level effect on the wave function renormalization of the Higgs field, and (iii) SMEFT top-quark one-loop level effect. The sensitivity of future gravitational wave observations to these effects is numerically calculated by performing a Fisher matrix analysis. We find that the future gravitational wave observations can be sensitive to (ii) and (iii) once the first-order electroweak phase transition arises from (i). The dimension-eight ${\phi }^8$ operator effects on the first-order electroweak phase transition are also discussed. The sensitivities of the future gravitational wave observations are also compared with those of future collider experiments.

An analysis of the geometry and structure of center vortices in the presence of dynamical fermions is performed. A variety of metrics are used to measure the matrix structure of the vortex-modified gauge fields. Visualizations of center vortices are presented and percolating clusters are identified. The size of secondary vortex clusters is analyzed, with substantial differences observed between the pure Yang-Mills and dynamical fermion case. Vortex fields are represented as directed graphs, with branching points acting as the vertices. This representation leads to a novel picture of vortex branching as a binomial process. These results elucidate the change in the center vortex vacuum induced by the introduction of dynamical fermions.

In the absence of interactions the conductivity of the chiral separation effect (CSE) in the system of massless fermions is given by a topological expression; interactions might change the pattern drastically. However, we prove that the CSE conductivity is still given by the topological invariant composed of the Green functions at zero temperature as long as the chiral symmetry is present, and if the renormalized axial current is considered. This allows us to predict its appearance with the standard value of conductivity per the Dirac fermion ${\sigma }_{\mathrm{CSE}}=\frac{1}{2{\pi }^2}$ in quark-gluon matter at $T=0$ and sufficiently large baryon chemical potential, in the hypothetical phase with restored chiral symmetry and without color superconductivity. This phase may be realized inside the neutron stars. We also argue that the same topological expression for the CSE may be observed in Weyl semimetals, which realize the system of interacting relativistic fermions in solid state systems. In order to estimate the nonperturbative corrections to ${\sigma }_{\mathrm{CSE}}$ within QCD at finite temperatures we apply the method of field correlators developed by Yu. A. Simonov. As expected, above the deconfinement crossover, the topological expression is approached within the quark-gluon plasma phase, when the quark chemical potential is sufficiently large. However, we observe that this occurs only when quark chemical potential is much larger than the thermal (Debye) mass. This range of parameters appears to be far out of the region accessible at the modern colliders.

Lorentz and $CPT$ symmetry in the quark sector of the Standard Model are studied in the context of an effective field theory using ZEUS $e^{\pm }p$ data. Symmetry-violating effects can lead to time-dependent oscillations of otherwise time-independent observables, including scattering cross sections. An analysis using five years of inclusive neutral-current deep inelastic scattering events corresponding to an integrated HERA luminosity of $372{\mathrm{pb}}^{-1}$ at $\sqrt{s}=318\mathrm{GeV}$ has been performed. No evidence for oscillations in sidereal time has been observed within statistical and systematic uncertainties. Constraints, most for the first time, are placed on 42 coefficients parametrizing dominant $CPT$-even dimension-four and $CPT$-odd dimension-five spin-independent modifications to the propagation and interaction of light quarks.

It is a long-standing problem in general relativity that the notion of angular momentum of an isolated system has supertranslation ambiguity. In this paper, we argue that the ambiguity is essentially because of the gravitational wave memory. When properly subtracting the memory effect of the observer, one can introduce a supertranslation invariant definition of the angular momentum at null infinity even for dynamical process.