We present a covariant quantum formalism for scalar particles based on an enlarged Hilbert space. The particular physical theory can be introduced through a timeless Wheeler DeWitt-like equation, whose projection onto four-dimensional coordinates leads to the Klein-Gordon equation. The standard quantum mechanical product in the enlarged space, which is invariant and positive definite, implies the usual Klein-Gordon product when applied to its eigenstates. Moreover, the standard three-dimensional invariant measure emerges naturally from the flat measure in four dimensions when mass eigenstates are considered, allowing a rigorous identification between definite mass history states and the standard Wigner representation. Connections with the free propagator of scalar field theory and localized states are subsequently derived. The formalism also allows the superposition of different theories and remains valid in the presence of a fixed external field, revealing special orthogonality relations. Other details such as extended identities for the current density, the quantization of parameterized theories and the nonrelativistic limit, with its connection to the Page and Wooters formalism, are discussed. A related consistent second quantization formulation is also introduced.

By replacing the scalar $\varphi$ with $i\varphi$ in the solution constructed by Huang et al. [Static and dynamic charged black holes, Eur. Phys. J. C 79, 975 (2019).], we obtain electrically charged wormhole and black hole solutions in the Einstein-Maxwell-scalar theory, in which the scalar is a phantom field coupled to the Maxwell field nonminimally. Our solutions are simpler than the previously known charged wormholes in the Einstein-Maxwell-dilaton theory in that both the scalar and the radius of the foliating sphere of our solutions are independent of electric charge. The wormhole solution has two asymptotically flat regions and reduces to the Ellis wormhole when the charge is zero. We draw the embedding diagrams for the wormholes and demonstrate that the two sides are asymmetric. As the charge increases, horizons will appear, and the wormhole becomes a black hole, with no curvature singularity but a wormhole throat or a bounce. We analyze black hole thermodynamics and the causal structure. We also determine the photon spheres of both the wormhole and the black hole and discuss their observable characteristics.

Recently, Sorce and Wald have suggested a new version of the gedanken experiments to overspin or overcharge the Kerr-Newman black holes in Einstein-Maxwell gravity. Following their setup, in this paper, we investigate the weak cosmic censorship conjecture in the static Einstein-Born-Infeld black holes for the Einstein gravity coupled to nonlinear electrodynamics. First of all, we derive the first second order perturbation inequalities of the charged collision matter in the Einstein-Born-Infeld gravity based on the Iyer-Wald formalism as well as the null energy conditions of the matter fields and show that they share the same form as these in Einstein-Maxwell gravity. As a result, we find that the static Einstein-Born-Infeld black holes cannot be overcharged under the second-order approximation after considering these inequalities. Our result at some level hints at the validity of the weak cosmic censorship conjecture for string theory.

Nonlocal RT gravity is a successful modified gravity theory, which not only explains the late-time cosmic acceleration but also behaves well in the Solar System. Previous analysis generally assumes the auxiliary field $S_i$ vanishes at the cosmic background. However, we find the background $S_i$ is proportional to $a^2$ with the expansion of the Universe. Then, we discuss the influence of the nonzero background $S_i$ on the cosmic background evolution and the scalar and tensor perturbations. We find the cosmic background evolution is independent of $S_i$, and the influence of the nonzero background $S_i$ on the weak field limit at Solar System scales is negligible. For the tensor perturbation, we find the only possible observable effect is the influence of nonzero background $S_i$ on the LIGO gravitational wave amplitude and also luminosity distance. Future high-redshift gravitational wave observations could be used to constrain the background value of $S_i$.

The Universe’s early thermal history is poorly constrained, and it is possible that it underwent a period of early matter domination driven by a heavy particle or an oscillating scalar field that decayed into radiation before the onset of big bang nucleosynthesis. The entropy sourced by this particle’s decay reduces the cross section required for thermal-relic dark matter to achieve the observed abundance. This degeneracy between dark matter properties and the thermal history vastly widens the field of viable dark matter candidates, undermining efforts to constrain dark matter’s identity. Fortunately, an early matter-dominated era also amplifies density fluctuations at small scales and leads to early microhalo formation, boosting the dark matter annihilation rate and bringing smaller cross sections into the view of existing indirect-detection probes. Employing several recently developed models of microhalo formation and evolution, we develop a procedure to derive indirect-detection constraints on dark matter annihilation in cosmologies with early matter domination. This procedure properly accounts for the unique morphology of microhalo-dominated signals. While constraints depend on dark matter’s free-streaming scale, the microhalos make it possible to obtain upper bounds as small as $⟨\sigma v⟩\lesssim {10}^{-32}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ using Fermi-LAT observations of the isotropic gamma-ray background and the Draco dwarf galaxy.

Thermodynamics on the horizon of a flat universe at late times is studied in holographic cosmological models that assume an associated entropy on the horizon. In such models, a $\mathrm{\Lambda }(t)$ model similar to a time-varying $\mathrm{\Lambda }(t)$ cosmology is favored because of the consistency of energy flows across the horizon. Based on this consistency, a $\mathrm{\Lambda }(t)$ model with a power-law term proportional to $H^{\alpha }$ is formulated to systematically examine the evolution of the Bekenstein-Hawking entropy. Here, $H$ is the Hubble parameter and $\alpha$ is a free parameter whose value is a real number. The present model always satisfies the second law of thermodynamics on the horizon. In particular, the universe for $\alpha <2$ tends to approach thermodynamic equilibriumlike states. Consequently, when $\alpha <2$, the maximization of the entropy should be satisfied as well, at least in the last stage of the evolution of an expanding universe. A relaxationlike process before the last stage is also examined from a thermodynamics viewpoint.

In the presence of the local-type primordial non-Gaussianity, it is known that the clustering of primordial black holes (PBHs) emerges even on superhorizon scales at the formation time. This effect has been investigated in the high-peak limit of the PBH formation in the radiation-dominated epoch in the literature. There is another possibility that the PBH formation takes place in the early matter-dominated epoch. In this scenario, the high-peak limit is not applicable because even initially small perturbations grow and can become a PBH. We first derive a general formula to estimate the clustering of PBHs with primordial non-Gaussianity without assuming the high-peak limit and then apply this formula to a model of PBH formation in a matter-dominated epoch. Clustering is less significant in the case of the PBH formation in the matter-dominated epoch than that in the radiation-dominated epoch. Nevertheless, it is much larger than the Poisson shot noise in many cases. Relations to the constraints of the isocurvature perturbations by the cosmic microwave background radiation are quantitatively discussed.

We analyze the impact of various boundary conditions on the (minisuperspace) Lorentzian gravitational path integral. In particular, we assess the implications for the Hartle-Hawking no-boundary wave function. It was shown recently that when this proposal is defined as a sum over compact metrics, problems arise with the stability of fluctuations. These difficulties can be overcome by an especially simple implementation of the no-boundary idea, namely, taking the Einstein-Hilbert action at face value while adding no boundary term. This prescription simultaneously imposes an initial Neumann boundary condition for the scale factor of the Universe and, for a Bianchi IX spacetime, Dirichlet conditions for the anisotropies. Another way to implement the no-boundary wave function is to use Robin boundary conditions. A subclass of Robin conditions allows one to specify the Hubble rate on the boundary hypersurface, and we highlight the surprising aspect that specifying the final Hubble rate (rather than the final size of the Universe) significantly alters the off-shell structure of the path integral. The conclusion of our investigations is that all current working examples of the no-boundary wave function force one to abandon the notion of a sum over compact and regular geometries, and point to the importance of an initial Euclidean momentum.

We study the impact of the fermion vacuum term in the SU(3) quark meson model on the equation of state and determine the vacuum parameters for various sigma meson masses. We examine its influence on the equation of state and on the resulting mass radius relations for compact stars. The tidal deformability $\mathrm{\Lambda }$ of the stars is studied and compared to the results of the mean field approximation. Parameter sets which fulfill the tidal deformability bounds of GW170817 together with the observed two solar mass limit turn out to be restricted to a quite small parameter range in the mean field approximation. The extended version of the model does not yield solutions fulfilling both constraints. Furthermore, no first order chiral phase transition is found in the extended version of the model, not allowing for the twin star solutions found in the mean field approximation.

The orbital period of a compact binary system decays mainly due to quadrupole gravitational radiation, which agrees with the observation to within 1%. Other types of radiation such as ultralight scalar or pseudoscalar radiation and massive vector boson radiation also contribute to the decay of the orbital period as long as the mass of the emitted particle is less than the orbital frequency of the compact binary system. We obtain an expression of the energy loss due to the radiation of the massive vector field from the neutron star–neutron star and neutron star–white dwarf binaries. Because of the large chemical potential of the degenerate electrons, neutron stars (NSs) have large muon charge. We derive the energy loss due to $U(1{)}_{L_{\mu }-L_{\tau }}$ gauge boson radiation from the binaries. For the radiation of the vector boson, the mass is restricted by $M_{Z^{\prime }}<\mathrm{\Omega }\simeq {10}^{-19}\mathrm{eV}$, which are the orbital frequencies of the compact star binaries. Using the formula of orbital period decay, we obtain constraints on the coupling constant of the gauge boson in the gauged $L_{\mu }-L_{\tau }$ theory for the four compact binary systems. For vector gauge boson muon coupling, we find that for $M_{Z^{\prime }}<{10}^{-19}\mathrm{eV}$, the constraint on the coupling constant is $g<\mathcal{O}({10}^{-20})$. We also obtain the exclusion plots of the massive vector Proca field and the gauge field which can couple to muons.

We examine the uncertainty of the calculation of the atmospheric neutrino flux due to the uncertainty in the hadronic interaction, and present a way to reduce it using accurately measured atmospheric muon flux. Considering the difference in the hadronic interaction model and the real one as a variation of hadronic interaction, we find a quantitative estimation method for the error of the atmospheric neutrino flux calculation from the reconstruction residual of the atmospheric muon flux observed in a precision experiment. However, the relation of the calculation error of the neutrino flux and the reconstruction residual of the muon flux is largely dependent on the atmospheric muon observation site, especially for the low energy neutrinos. We study the relation at several observation sites, near Kamioka at sea level, same but 2770 m a.s.l., Hanle India (4500 m a.s.l.), and at Balloon altitude ($\sim 32\mathrm{km}$). Then, we estimate how stringently the atmospheric muon can reduce the calculation error of the atmospheric neutrino flux. We also discuss briefly on the source of error which is considered to be difficult to reduce only by the atmospheric muon data.

We consider the decoherence effects in the propagation of neutrinos in a background composed of a scalar particle and a fermion due to the nonforward neutrino scattering processes. Using a simple model for the coupling of the form ${\overline{f}}_R{\nu }_L\varphi$, we calculate the contribution to the imaginary part of the neutrino self-energy arising from the nonforward neutrino scattering processes in such backgrounds, from which the damping terms are determined. In the case we are considering, in which the initial neutrino state is depleted but does not actually disappear (the initial neutrino transitions into a neutrino of a different flavor but does not decay into a $f\varphi$ pair, for example), we associate the damping terms with decoherence effects. For this purpose, we give a precise prescription to identify the decoherence terms, as used in the context of the master or Linblad equation, in terms of the damping terms we have obtained from the calculation of the imaginary part of the neutrino self-energy from the nonforward neutrino scattering processes. The results can be directly useful in the context of dark matter-neutrino interaction models in which the scalar and/or fermion constitute the dark matter and can also serve to guide the generalizations to other models and/or situations in which the decoherence effects in the propagation of neutrinos originate from the nonforward scattering processes may be important. As a guide to estimating such decoherence effects, the contributions to the absorptive part of the self-energy and the corresponding damping terms are computed explicitly in the context of the model we consider, for several limiting cases of the momentum distribution functions of the background particles.

By considering a flavor expansion about the $SU(3)$ flavor symmetric point, we investigate how flavor blindness constrains octet baryon matrix elements after $SU(3)$ is broken by the mass difference between quarks. Similarly to hadron masses we find the expansions to be constrained along a mass trajectory where the singlet quark mass is held constant, which provides invaluable insight into the mechanism of flavor symmetry breaking and proves beneficial for extrapolations to the physical point. Expansions are given up to third order in the expansion parameters. Considering higher orders would give no further constraints on the expansion parameters. The relation of the expansion coefficients to the quark-line-connected and quark-line-disconnected terms in the three-point correlation functions is also given. As we consider Wilson cloverlike fermions, the addition of improvement coefficients is also discussed and shown to be included in the formalism developed here. As an example of the method we investigate this numerically via a lattice calculation of the flavor-conserving matrix elements of the vector first-class form factors.

We investigate the equal-time (static) quark propagator in Coulomb gauge within the Hamiltonian approach to QCD. We use a non-Gaussian vacuum wave functional which includes the coupling of the quarks to the spatial gluons. The expectation value of the QCD Hamiltonian is expressed by the variational kernels of the vacuum wave functional by using the canonical recursive Dyson-Schwinger equations (CRDSEs) derived previously. Assuming the Gribov formula for the gluon energy we solve the CRDSE for the quark propagator in the bare-vertex approximation together with the variational equations of the quark sector. Within our approximation the quark propagator is fairly insensitive to the coupling to the spatial gluons and its infrared behavior is exclusively determined by the strongly infrared diverging instantaneous color Coulomb potential.

We perform the general relativistic stability analysis against adiabatic radial oscillations of unpaired quark stars obtained using the equation of state for cold quark matter from perturbative QCD, the only free parameter being the renormalization scale. This approach consistently incorporates the effects of interactions and includes a built-in estimate of the inherent systematic uncertainties in the evaluation of the equation of state. We also take into account the constraints imposed by the recent gravitational wave event GW170817 to the compact star masses and radii, and restrict their vibrational spectrum.

We investigate the role of anomalous gauge boson and fermion couplings in the production of $WZ$ and $W^{+}{W}^{-}$ pairs at the LHC to next-to-leading-order (NLO) QCD in the Standard Model effective field theory (SMEFT), including dimension-six operators. Our results are implemented in a publicly available version of the powheg-box. We combine our $WZ$ results in the leptonic final state $e\nu {\mu }^{+}{\mu }^{-}$ with previous $W^{+}{W}^{-}$ results to demonstrate the numerical effects of NLO QCD corrections on the limits on effective couplings derived from ATLAS and CMS 8 and 13 TeV differential measurements. Our study demonstrates the importance of including NLO QCD SMEFT corrections in the $WZ$ analysis, while the effects on $WW$ production are smaller. We also show that the $\mathcal{O}(1/{\mathrm{\Lambda }}^4)$ contributions dominate the analysis, where $\mathrm{\Lambda }$ is the high-energy scale associated with the SMEFT.

Using the data sample of $711{\mathrm{fb}}^{-1}$ of $\mathrm{\Upsilon }(4S)$ on-resonance data taken by the Belle detector at the KEKB asymmetric-energy electron-positron collider, we present the first measurements of branching fractions of the decays $B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c^{\prime 0}$, $B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c(2645{)}^0$, and $B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c(2790{)}^0$. The signal yields for these decays are extracted from the recoil mass spectrum of the system recoiling against ${\overline{\mathrm{\Lambda }}}_c^{-}$ baryons in selected $B^{-}$ candidates. The branching fraction of $B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c(2790{)}^0$ is measured to be $(1.1\pm 0.4\pm 0.2)\times {10}^{-3}$, where the first uncertainty is statistical and the second is systematic. The 90% credibility level upper limits on $\mathcal{B}(B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c^{\prime 0})$ and $\mathcal{B}(B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c(2645{)}^0)$ are determined to be $6.5\times {10}^{-4}$ and $7.9\times {10}^{-4}$, respectively.

Neutrino- and antineutrino-oxygen neutral-current quasielasticlike interactions are measured at Super-Kamiokande using nuclear deexcitation $\gamma$ rays to identify signal-like interactions in data from a $14.94(16.35)\times {10}^{20}$ protons-on-target exposure of the T2K neutrino (antineutrino) beam. The measured flux-averaged cross sections on oxygen nuclei are $⟨{\sigma }_{\nu \text{−}\mathrm{NCQE}}⟩=1.70\pm 0.17(\mathrm{stat}.{)}_{-0.38}^{+0.51}(\mathrm{syst}.)\times {10}^{-38}{\mathrm{cm}}^2/\text{oxygen}$ with a flux-averaged energy of 0.82 GeV and $⟨{\sigma }_{\overline{\nu }\text{−}\mathrm{NCQE}}⟩=0.98\pm 0.16(\mathrm{stat}.{)}_{-0.19}^{+0.26}(\mathrm{syst}.)\times {10}^{-38}{\mathrm{cm}}^2/\text{oxygen}$ with a flux-averaged energy of 0.68 GeV, for neutrinos and antineutrinos, respectively. These results are the most precise to date, and the antineutrino result is the first cross section measurement of this channel. They are compared with various theoretical predictions. The impact on evaluation of backgrounds to searches for supernova relic neutrinos at present and future water Cherenkov detectors is also discussed.

Gravitational waves (GWs) provide an excellent opportunity to test the gravity in the strong gravitational fields. In this article, we calculate the waveform of GWs, produced by the coalescence of compact binaries, in an extension of the Chern-Simons gravity by including higher derivatives of the coupling scalar field. By comparing the two circular polarization modes, we find the effects of amplitude birefringence and velocity birefringence of GWs in their propagation caused by the parity violation in gravity, which are explicitly presented in the GW waveforms by the amplitude and phase modifications, respectively. Combining the two modes, we obtain the GW waveforms in the Fourier domain and find that the deviations from those in general relativity are dominated by effects of velocity birefringence of GWs. In addition, we also map the effects of the parity violation on the waveform onto the parametrized post-Einsteinian (PPE) framework and identify explicitly the PPE parameters.

The possibility of neutron-mirror neutron transition has recently been discussed both from theoretical and experimental perspectives. We point out that such a transition would imply mass loss in neutron stars leading to a significant change of the orbital period of neutron star binary systems. Known limits on the period changes of such binaries therefore put strong limits on the above transition rate and hence on the $n-n^{\prime }$ mixing parameter ${\epsilon }^{\prime }$. These considerations exclude a large range of ${\epsilon }^{\prime }$ even if the $n-n^{\prime }$ mass difference is $\delta m^{\prime }$ as large as a few MeV. Our limits also exclude a large range of the values required to explain the neutron decay anomaly via $n-n^{\prime }$ mixing.