In the present work, we derive the motion of light in the weak-field limit of energy-momentum-squared gravity (EMSG). To do so, we introduce the post-Newtonian expansion of this modified theory of gravity. It is shown that, in addition to the Newtonian potential, a new EMSG potential affects the trajectory of photons. As a result, in this theory, photons do not behave as predicted by general relativity (GR). To evaluate the EMSG theory by the Solar System tests, we study light deflection and Shapiro time delay. Regarding the results obtained in Bertotti et al. [Nature (London) 425, 374 (2003)] and Shapiro et al. [Phys. Rev. Lett. 92, 121101 (2004)], we restrict the free parameter of the theory and show that it lies within the range $-4.0\times {10}^{-27}\mathrm{m}{\mathrm{s}}^2{\mathrm{kg}}^{-1}<f_0^{\prime }<8.7\times {10}^{-26}\mathrm{m}{\mathrm{s}}^2{\mathrm{kg}}^{-1}$. This interval is in agreement with those derived in Nazari et al. [Phys. Rev. D 105, 044014 (2022)] and Akarsu et al. [Phys. Rev. D 97, 124017 (2018)]. This consistency manifests that this theory passes these Solar System tests with flying colors. Interestingly, it turns out that the magnitude of the EMSG correction strongly depends on the density of the deflector. So, we investigate the possible effects of EMSG on images of a light source microlensed by a compact dense object such as neutron stars. It is estimated that the EMSG correction to the position of lensed images could be as large as (1–0.1) microarcseconds, which may be detected by future high-resolution missions. Moreover, the total magnification and the shape of light curves are obtained in the EMSG theory. It is revealed that except for a small deviation, the overall behavior of the EMSG light curves is similar to that in GR. We also show that as long as the light source and the dense lens are aligned, the EMSG correction is effective, and the combined light of the lensed images is different from the GR case. This issue makes it possible to observe signatures of this theory in the microlensing regime.

In this article, we continue the work on translating elements of the perturbative quantum field theory defined on Minkowski spacetime into the background independent framework of loop quantum gravity. We present the construction of r-Fock measures for $SU(N)$ gauge theories and represent the Fock vacuum of $SU(N)$ gauge fields on the loop quantum gravity Hilbert space. We treat the case of $SU(2)$ explicitly and provide a relation between these new r-Fock measures and the difeomorphism invariant measure used in loop quantum gravity.

We consider a nonminimally coupled scalar field as a potential cold dark matter candidate. These models are natural extensions of the ultralight axion models which are based on minimally coupled scalar fields. Such ultralight scalar fields are motivated by string theory and, in particular, have been studied in the context of the axiverse scenario. For a nonminimally coupled field, the scalar-field energy density behaves as radiation at early times, which yields a bound on the coupling constant, $\xi \lesssim 10$, from the primordial nucleosynthesis theory. The first-order perturbations of the nonminimally coupled field with adiabatic initial conditions cause the gravitational potential to decay on large scales. A comparison of the cosmological data with the theoretical matter power spectrum yields the following constraint on the coupling constant: $\xi \lesssim 0.01$. We also consider isocurvature modes in our analysis. We argue that a mix of adiabatic and isocurvature initial conditions for a nonminimally coupled scalar field might allow one to obtain the usual adiabatic CDM power spectrum.

We revisit the model of axion inflation in the context of stochastic inflation and investigate the effects of the stochastic noise associated to the electromagnetic fields. Because of the parity-violating interaction, one polarization of the gauge field is amplified inducing a large curvature perturbation power spectrum. Taking into account the stochastic kicks arising from the short modes at the time of horizon crossing we obtain the corresponding Langevin equations for the long modes of the electromagnetic and axion fields. It is shown that a mean-reverting process governs the dynamics of the electromagnetic fields such that the tachyonic growth of the gauge fields is balanced by the diffusion forces. As the instability parameter grows towards the end of inflation, the large curvature perturbations induced from gauge field perturbations lead to a copious production of small mass primordial black holes (PBHs). It is shown that the produced PBHs follow Gaussian statistics. Imposing the observational constraints on PBH formation relaxes the previous bounds on the instability parameter by about fifty percent.

The LHCb collaboration newly measured the decay rate of doubly charmed baryon ${\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Xi }}^{\prime +}{\pi }^{+}$, and a ratio of its branching fraction with respect to that of the decay ${\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Xi }}^{+}{\pi }^{+}$ is reported as $1.41\pm 0.17\pm 0.10$. This result conflicts with the theoretical predictions made by several groups. In our previous work, following the prescription given in early literature where the $us$ diquark in ${\mathrm{\Xi }}_c^{+}$ is assumed to be a scalar, whereas in ${\mathrm{\Xi }}_c^{\prime +}$ it is a vector, i.e., the spin-flavor structure of ${\mathrm{\Xi }}_c^{+}$ is $[us{]}_{0}c$ and that of ${\mathrm{\Xi }}_c^{\prime +}$ is $[us{]}_{1}c$, we studied the case of ${\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Xi }}^{(\prime )+}$ with the light-front quark model. Numerically we obtained $\mathrm{\Gamma }({\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Xi }}^{\prime +}{\pi }^{+})/\mathrm{\Gamma }({\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Xi }}^{+}{\pi }^{+})=0.56\pm 0.18$, which is about half of the data. While abandoning the presupposition, we suppose the spin-flavor structure of $[us]c$ in ${\mathrm{\Xi }}_c^{+}$ may be a mixture of $[us{]}_{0}c$ and $[us{]}_{1}c$, namely the spin-flavor function of ${\mathrm{\Xi }}_c^{+}$ could be $\cos \theta [us{]}_0[c]+\sin \theta [us{]}_1[c]$. An alternative combination $-\sin \theta [us{]}_0[c]+\cos \theta [us{]}_1[c]$ would correspond to ${\mathrm{\Xi }}_c^{\prime +}$. Introducing the mixing mechanism, the ratio $\mathrm{\Gamma }({\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Xi }}^{\prime +}{\pi }^{+})/\mathrm{\Gamma }({\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Xi }}^{+}{\pi }^{+})$ depends on the mixing angle $\theta$. With the mixing scenario, the theoretical prediction on the ratio between the transition rate of ${\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Xi }}_c^{\prime +}$ and that of ${\mathrm{\Xi }}_{cc}^{++}\to {\mathrm{\Xi }}_c^{+}$ can coincide with the data as long as $\theta =16.27°\pm 2.30°$ or $85.54°\pm 2.30°$ is set. Definitely, more precise measurements on other decay portals of ${\mathrm{\Xi }}_{cc}^{++}$ are badly needed for testing the mixing mechanism and further determining the mixing angle.

First-order phase transitions exist in many models beyond the Standard Model and can generate detectable stochastic gravitational waves for a strong one. Using the cosmological observables in big bang nucleosynthesis and cosmic microwave background, we derive constraints on the phase transition temperature and strength parameter in a model-independent way. For a strong phase transition, we find that the phase transition temperature should be above around 2 MeV for both reheating photon and neutrino cases. For a weak one with the temperature below 1 MeV, the phase transition strength parameter is constrained to be smaller than around 0.1. Implications for using a first-order phase transition to explain the NANOGrav observed signal are also discussed.

In this paper we develop a quantum theory of synchrotron radiation of massive and massless fermions in ($2+1$)-dimensional electrodynamics with a doubled fermionic representation based on an exact formula for the radiation shift of electron energy in a constant magnetic field. Analytical formulas describing the dependences of the spectral distribution and the total radiation power of a massive fermion on the dynamic parameter of synchrotron radiation and the spin quantum number of the initial electron are obtained. The power of synchrotron radiation of a massless charged fermion is calculated in the case of large values of the main quantum number and a relatively weak magnetic field. It was shown that the radiation power of a massless fermion is described by a formula that coincides with the main term of the asymptotic expansion of the radiation power of a massive electron in the ultraquantum case.

Discrete symmetries are widely imposed in particle theories. It is well known that the spontaneous breaking of discrete symmetries leads to domain walls. Current studies of domain walls have focused on those from the spontaneous breaking of a $Z_2$ symmetry. Larger discrete symmetries have multiple degenerate vacua, leading to domain walls which are in principle different from the simplest $Z_2$ domain wall. We take domain walls from $Z_N$ symmetry breaking as an illustrative study, and study in detail the $Z_3$ case, in which semianalytical results for the tension and thickness of domain walls are derived. Explicit symmetry-breaking terms lead to the dynamics of domain walls collapsing in a more more complicated way than the $Z_2$ case. Gravitational wave signals deviate from those from $Z_2$ domain walls.

We designed a protocol for digital quantum computation of a gauge theory with a topological term in Minkowski spacetime, which is practically inaccessible by standard lattice Monte Carlo simulations. We focus on $1+1$ dimensional quantum electrodynamics with the $\theta$ term known as the Schwinger model and test our protocol for this on an IBM simulator. We construct the true vacuum state of a lattice Schwinger model using adiabatic state preparation which, in turn, allows us to compute an expectation value of the fermion mass operator with respect to the vacuum. Upon taking a continuum limit we find that our result in the massless case agrees with the known exact result. In the massive case, we find an agreement with mass perturbation theory in the small-mass regime and deviations in the large-mass regime. We estimate computational costs required to take a reasonable continuum limit. Our results imply that digital quantum simulation appears a promising tool to explore nonperturbative aspects of gauge theories with real time and topological terms.

Lattice quantum chromodynamics (LQCD) has the promise of constraining low-energy constants (LECs) of nuclear effective field theories (EFTs) from first-principles calculations that incorporate the dynamics of quarks and gluons. Given the Euclidean and finite-volume nature of LQCD outputs, complex mappings are developed in recent years to obtain the Minkowski and infinite-volume counterparts of LQCD observables. In particular, as LQCD is moving toward computing a set of important few-nucleon matrix elements at the physical values of the quark masses, it is important to investigate whether the anticipated precision of LQCD spectra and matrix elements will be sufficient to guarantee tighter constraints on the relevant LECs than those already obtained from phenomenology, considering the nontrivial mappings involved. With a focus on the leading-order LECs of the pionless EFT, $L_{1,A}$ and $g_{\nu }^{NN}$, which parametrize, respectively, the strength of the isovector axial two-body current in a single-$\beta$ decay (and other related processes such $pp$ fusion), and of the isotensor contact two-body operator in the neutrinoless double-$\beta$ decay within the light neutrino exchange scenario, the expected uncertainty on future extractions of $L_{1,A}$ and $g_{\nu }^{NN}$ are examined using synthetic data at the physical values of the quark masses. It is observed that achieving small uncertainties in $L_{1,A}$ will be challenging, and (sub)percent-level precision in the two-nucleon spectra and matrix elements is essential in reducing the uncertainty on this LEC compared to the existing constraints. On the other hand, the short-distance coupling of the neutrinoless double-$\beta$ decay, $g_{\nu }^{NN}$, is shown to be less sensitive to uncertainties on both LQCD energies and the matrix element, and can likely be constrained with percent-level precision in the upcoming LQCD calculations.

Manifestly Lorentz-invariant baryon chiral perturbation theory is used to calculate the radiative correction of low energy elastic lepton proton scatterings. Corrections of differential cross section and charge asymmetry are given at chiral next-to-leading order $(\mathcal{O}(p^2))$ with a nonzero lepton mass, which are infrared and ultraviolet finite. The results are basically consistent with previous predictions based on hadron model calculation, but they are somewhat different from calculations based on heavy baryon chiral perturbation theory, especially in charge asymmetry.

The potential for using slow-fluor liquid scintillators to study low energy solar neutrinos and neutrinoless double beta decay ($0\nu \beta \beta$) is explored through a series of simulations. The fluorescence model assumed for the primary fluor has characteristics similar to acenaphthene, recently used to demonstrate Cherenkov separation at energies around 1 MeV [Nucl. Instrum. Methods Phys. Res., Sect. A 972, 164106 (2020)]. Results here indicate notably better directional reconstruction in large-scale detectors than has previously been suggested by other approaches, allowing better identification of low energy solar neutrinos. These studies indicate that a detector with as little as $\sim 30\%$ coverage using currently available photomultiplier tubes could be able to make a measurement of the CNO solar neutrino flux to a precision of better than 10% (enough to distinguish metallicity models) with a few kiloton-years of exposure. In terms of $0\nu \beta \beta$, studies here suggest that the ability to separate mechanisms based on angular distributions is weak, but that the rejection of solar neutrino backgrounds with such a technique might potentially approach a factor of 10 for endpoint energies near 2.5 MeV in the angular hemisphere defined by the solar direction.

Superfluid ${}^4\mathrm{He}$ is a promising target material for direct detection of light ($<1\mathrm{GeV}$) dark matter. Possible signal channels available for readout in this medium include prompt photons, triplet excimers, and roton and phonon quasiparticles. The relative yield of these signals has implications for the sensitivity and discrimination power of a superfluid ${}^4\mathrm{He}$ dark matter detector. Using a $16{\mathrm{cm}}^3$ volume of 1.75 K superfluid ${}^4\mathrm{He}$ read out by six immersed photomultiplier tubes, we measured the scintillation from electronic recoils ranging between 36.3 and $185{\mathrm{keV}}_{\mathrm{ee}}$, yielding a mean signal size of ${1.25}_{-0.03}^{+0.03}\mathrm{phe}/{\mathrm{keV}}_{\mathrm{ee}}$, and nuclear recoils from 53.2 to $1090{\mathrm{keV}}_{\mathrm{nr}}$. We compare the results of our relative scintillation yield measurements to an existing semiempirical model based on helium-helium and electron-helium interaction cross sections. We also study the behavior of delayed scintillation components as a function of recoil type and energy, a further avenue for signal discrimination in superfluid ${}^4\mathrm{He}$.

We introduce the notion of genus-one data for theories in ($1+1$) dimensions with an anomalous finite group global symmetry. We outline the groups for which genus-one data are effective in detecting the anomaly and also show that genus-one data are insufficient to detect the anomaly for dicyclic groups.

We clarify relations among topological solitons in various dimensions: a domain wall, non-Abelian vortex, magnetic monopole, and Yang-Mills instanton, together with a (non-Abelian) sine-Gordon soliton, baby skyrmion (lump), and skyrmion. We construct a composite configuration consisting of a domain wall, vortex, magnetic monopole, and Yang-Mills instanton (wall-vortex-monopole-instanton) using the effective theory technique or moduli approximation. Removing some solitons from such a composite, we obtain all possible composite solitons in the form of solitons within a soliton, including all the previously known configurations, yielding relations among topological solitons.

We propose a new approach to study the phase transition dynamics of the Reissner-Nordström-AdS black holes on the underlying free energy landscape. By formulating a path integral framework, we quantify the kinetic paths representing the histories from the initial state to the end state, which provides us a visualized, yet quantified, picture about how the phase transition proceeds. Based on these paths, we derive the analytical formulas for the time evolution of the transition probability and provide a physical interpretation of the contribution to the probability from one pseudomolecule (antipseudomolecule), composed of instantons and anti-instantons, which is actually the phase transition rate from the small(large) to the large(small) black hole state. These numerical results show a good consistency with the underlying free energy landscape topography.

Ultracompact objects with photonspheres are known to mimic many observational features of black holes. It has been suggested that anomalous tidal heating or the presence of resonances in gravitational wave signals would be a clear imprint of a surface or absence of a horizon. Such claims and studies are all based on a frequency-domain analysis, assuming stationarity. Here we show that the object needs to first “fuel-up” until it reaches the stationary regime. The presence of a stable light ring and large light-travel times inside the object may in fact delay enormously the “charging-up” and effectively contribute to the effacement of structure. In other words, black hole mimickers behave as black holes more efficiently than previously thought. Our results have implications for other resonant systems with sharp resonances, including “floating orbits” around spinning black holes. A proper accounting of the self-force for such systems seems to be both mandatory, and would have important applications for tests of horizon physics.

We discuss cosmology based on a Cuscuta-Galileon gravity theory, which preserves just two degrees of freedom. Although there exist no additional degrees of freedom, introduction of a potential of a scalar field changes the dynamics. The scalar field is completely determined by matter fields. Giving an exponential potential as an example, we discuss the cosmological dynamics. The gravitational “constant” $G_{\mathrm{F}}$ appeared in the effective Friedmann equation becomes time dependent. We also present how to construct a potential when we know the evolution of the Hubble parameter. When we assume the $\mathrm{\Lambda }\mathrm{CDM}$ cosmology for the background evolution, we find the potential form. We then analyze the density perturbations, which equation is characterized only by a change of the gravitational “constant” $G_{\mathrm{eff}}$, which also becomes time dependent. From the observational constraints such as the constraint from the big-bang nucleosynthesis and the constraint on time-variation of gravitational constant, we restrict the parameters in our models. The time dependence of the gravitational constant in the effective Friedmann equation, we may have a chance to explain the Hubble tension problem.

The uniqueness theorem for static, spherically symmetric, asymptotically flat, and higher dimensional phantom black holes, with nondegenerate event horizon, being the solutions of Einstein phantom-dilaton Maxwell–anti-Maxwell gravity systems is considered. Conformal positive energy theorem and conformal transformations authorize the crucial tools for exploiting the boundary conditions and conformal flatness.

The Tolman VII solution is considered by some as one of the few analytical solutions to Einstein’s equations, which describes approximately well the interior of neutron stars (NSs). This solution is characterized by the mass $M$, radius $R$, and an energy density that varies quadratically with the radial coordinate $r$. Recently, Jiang and Yagi proposed a modification of this solution, the so-called modified Tolman VII (MTVII) solution, by introducing an additional quartic term to the energy density radial profile. The MTVII solution is an approximate solution to Einstein’s equation, which includes a new parameter $\alpha$ that allows the solution to have a better agreement with the energy density profiles for realistic NSs. Here we consider the MTVII solution, showing that for certain values of the parameter $\alpha$ and compactness $\mathcal{C}$ this solution manifests a region of negative pressure near the surface which leads to negative values of the tidal Love number. To alleviate these drawbacks, we introduce an exact version of the MTVII solution obtained by solving numerically Einstein’s equations for the MTVII energy density profile. As an application of our new exact MTVII (EMTVII) solution, we calculate the tidal Love number and tidal deformability, as a function of $\mathcal{C}$, for different values of the parameter $\alpha$. We find that the EMTVII solution predicts a positive tidal Love number for the whole range of allowed values of parameters $(\mathcal{C},\alpha )$, in agreement with previous results for realistic NSs.