We investigate the phenomenology of light GeV-scale fermionic dark matter in the $U(1{)}_{L_{\mu }-L_{\tau }}$ gauge extension of the Standard Model. Heavy neutral fermions alongside with a $S_1(\overline{3},1,1/3)$ scalar leptoquark and an inert scalar doublet are added to address the flavor anomalies and light neutrino mass respectively. The light gauge boson associated with the $U(1{)}_{L_{\mu }-L_{\tau }}$ gauge group mediates a dark to visible sector and helps to obtain the correct relic density. Aided with a colored scalar, we constrain the new model parameters by using the branching ratios of various $b\to sll$ and $b\to s\gamma$ decay processes as well as the lepton flavor nonuniversality observables $R_{K^{(*)}}$ and then show the implication on the branching ratios of some rare semileptonic $B\to (K^{(*)},\varphi )+$ missing energy processes.

In the present work, we study the production problem of the charmed baryon ${\mathrm{\Lambda }}_c(2860{)}^{+}$ at $\overline{\mathrm{P}}\mathrm{ANDA}$. With the $J^P={\frac{3}{2}}^{+}$ assignment to ${\mathrm{\Lambda }}_c(2860{)}^{+}$, an effective Lagrangian approach is adopted to calculate the cross section of $p\overline{p}\to {\mathrm{\Lambda }}_c^{-}{\mathrm{\Lambda }}_c(2860{)}^{+}$. The Dalitz plot analysis and the $D^{0}p$ invariant mass spectrum distribution are also given for the $p\overline{p}\to {\mathrm{\Lambda }}_c^{-}{\mathrm{\Lambda }}_c(2860{)}^{+}\to {\mathrm{\Lambda }}_c^{-}p{D}^0$ process. The numerical results show that the total cross section may reach up to about $10\mu \mathrm{b}$. With the designed luminosity of $\overline{\mathrm{P}}\mathrm{ANDA}$ ($2\times {10}^{32}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$), about ${10}^8{\mathrm{\Lambda }}_c(2860)$ events can be expected per day by reconstructing the final $p{D}^0$.

We demonstrate how $S$-matrix poles manifest themselves as the physical spectrum near the upper threshold in the context of the two-channel uniformized Mittag-Leffler expansion, an expression written as a sum of pole terms (Mittag-Leffler expansion) under an appropriate variable where the $S$ matrix is made single-valued (uniformization). We show that the transition of the spectrum is continuous as a $S$-matrix pole moves across the boundaries of the complex energy Riemann sheets and that the physical spectrum peaks at or near the upper threshold when the $S$-matrix pole is positioned sufficiently close to it on the uniformized plane. There is no essential difference on which sheet the pole is positioned. What is important is the existence of a pole near the upper threshold and the distance between the pole and the physical region, not on which complex energy sheet the pole is positioned. We also point out that when the pole is close to the upper threshold, the complex pole does not have the usual meaning of the resonance. Neither the real part represents the peak energy, nor the imaginary part represents the half width. Subsequently, we try to understand the current status of $Z(3900)$ from the viewpoint of the uniformized Mittag-Leffler expansion reflecting in particular, Phys. Rev. Lett. 117, 242001 (2016) in which they concluded that $Z(3900)$ is not a conventional resonance but a threshold cusp. We point out that their results turn out to indicate the existence of $S$-matrix poles near the $\overline{D}{D}^{*}$ threshold, which is most likely the origin of the peak found in their calculation of the near-threshold spectrum. In order to support our argument, we set up a separable potential model which shares common behavior of poles near the $\overline{D}{D}^{*}$ threshold to the above-mentioned reference and show in our model that the structures near the $\overline{D}{D}^{*}$ threshold are indeed caused by these near-threshold poles.

The exclusive production of vector mesons and photons in $ep$ collisions is investigated considering three phenomenological saturation models based on distinct assumptions for the treatment of the dipole-hadron scattering amplitude. The latest high precision HERA data for the reduced and vector meson cross sections are used to update the saturation model proposed by Marquet Peschanski, and Soyez, which predicts that the saturation scale is dependent of the squared momentum transfer $t$. The Marquet-Peschanski-Soyez predictions for the photon virtuality, energy and $t$ dependencies of the exclusive $\rho$, $J/\mathrm{\Psi }$, and deeply virtual Compton scattering cross sections are presented and a detailed comparison with the results derived using the impact parameter saturation models is performed. Our results indicate that a future experimental analysis of the $t$ distribution $d\sigma /dt$ for exclusive processes in the kinematical range that will covered by the EIC and LHeC, considering the distinct photon polarizations and large values of $t$, will be able to discriminate between the distinct approaches for the QCD dynamics at high energies.

We explore the nonadditive three-body quantum gravitational quadrupole interaction among three nonpointlike objects in their ground states in the framework of linearized quantum gravity and find that the interaction exhibits a distance behavior of $r_A^{-5}{r}_B^{-5}{r}_C^{-5}$ in the near regime where the interobject distances are small compared with the characteristic transition wavelength of the objects, and $r_A^{-5}{r}_B^{-5}{r}_C^{-5}(r_A+r_B+r_C{)}^{-1}$ in the far regime where the distances are larger than the characteristic transition wavelength, where $r_{\xi }$ denotes the distance between any two objects except object $\xi (\xi =A,B,C)$. Compared to the additive quantum gravitational interaction between two ground-state objects in vacuum, which is always attractive both in the near and far regimes, the nonadditive interaction among three ground-state objects can be either attractive or repulsive depending on the geometrical configuration of these objects. That is, in principle, the attractive or repulsive properties of the nonadditive three-body quantum gravitational interaction can be manipulated by changing the geometrical arrangement of the objects.

We derive the leading spin-dependent gravitational tail memory, which appears at the second post-Minkowskian order and behaves as $u^{-2}$ for large retarded time $u$. This result follows from the classical soft graviton theorem at order $\omega \ln \omega$ as a low-frequency expansion of the gravitational waveform with frequency $\omega$. First, we conjecture the gravitational waveform from the classical limit of the quantum soft graviton theorem up to sub-subleading order in a soft expansion, and then we derive it for a classical scattering process without any reference to the soft graviton theorem. We show that the final result of the gravitational waveform in the direct derivation completely agrees with the conjectured waveform.

It has recently been demonstrated numerically that spinning black holes whose dimensionless rotation parameter is larger than the critical value $(J/M^2{)}_{\mathrm{crit}}\equiv {\overline{a}}_{\mathrm{crit}}=\frac{1}{2}$ can support spatially regular hairy scalar configurations which are characterized by a nonminimal negative coupling to the Gauss-Bonnet curvature invariant. Motivated by this physically important observation, we explore, using analytical techniques, the physical and mathematical properties of the composed spinning-Kerr-black-hole-nonminimally-coupled-linearized-scalar-field configurations in the large-coupling $-\overline{\eta }\gg 1$ regime (here $\overline{\eta }$ is the dimensionless coupling parameter of the composed black-hole-scalar-field theory). In particular, we derive a remarkably compact analytical formula for the spin-dependent critical existence line ${\overline{\eta }}_{\mathrm{crit}}={\overline{\eta }}_{\mathrm{crit}}(\overline{a})$ of the composed black-hole-field system. The physical significance of this critical line stems from the fact that, for a given value of the black-hole dimensionless rotation parameter $\overline{a}$, it marks the boundary between bald (scalarless) Kerr black holes and nonlinearly coupled hairy spinning-black-hole-scalar-field configurations.

We study the potential of Bayesian neural networks (BNNs) to detect new physics in the dark matter power spectrum, concentrating here on evolving dark energy and modifications to general relativity. After introducing a new technique to quantify classification uncertainty in BNNs, we train two BNNs on mock matter power spectra produced using the publicly available code react in the $k$ range $(0.01-2.5)h{\mathrm{Mpc}}^{-1}$ and redshift bins (0.1, 0.478, 0.783, 1.5) with Euclid-like noise. The first network classifies spectra into five labels including $\mathrm{\Lambda }\mathrm{CDM}$, $f(R)$, $w\mathrm{CDM}$, Dvali-Gabadadze-Porrati gravity and a “random” class, whereas the second is trained to distinguish $\mathrm{\Lambda }\mathrm{CDM}$ from non-$\mathrm{\Lambda }\mathrm{CDM}$. Both networks achieve a comparable training, validation and test accuracy of $\sim 95\%$. Each network is also capable of correctly classifying spectra with deviations from $\mathrm{\Lambda }\mathrm{CDM}$ that were not included in the training set, demonstrated with spectra generated using the growth index $\gamma$. To obtain an indication of the BNNs classification capability, we compute the smallest deviation from $\mathrm{\Lambda }\mathrm{CDM}$ such that the noise-averaged non-$\mathrm{\Lambda }\mathrm{CDM}$ classification probability is at least 95% according to our estimated error quantification, finding these bounds to be $f_{R0}\lesssim {10}^{-7}$, ${\mathrm{\Omega }}_{\mathrm{rc}}\lesssim {10}^{-2}$, $-1.05\lesssim w_0\lesssim 0.95$, $-0.2\lesssim w_a\lesssim 0.2$, and $0.52\lesssim \gamma \lesssim 0.59$. The bounds on $f(R)$ can be improved by training a specialist network to distinguish solely between $\mathrm{\Lambda }\mathrm{CDM}$ and $f(R)$ power spectra which can detect a nonzero $f_{R0}$ at $\mathcal{O}({10}^{-8})$. We expect that further developments, such as the inclusion of smaller length scales or additional extensions to $\mathrm{\Lambda }\mathrm{CDM}$, will only improve the potential of BNNs to indicate the presence of new physics in cosmological datasets, regardless of the underlying theory.

One signature of an expanding universe is the time variation of the cosmological abundances of its different components. For example, a radiation-dominated universe inevitably gives way to a matter-dominated universe, and critical moments such as matter-radiation equality are fleeting. In this paper, we point out that this lore is not always correct and that it is possible to obtain a form of “stasis” in which the relative cosmological abundances ${\mathrm{\Omega }}_i$ of the different components remain unchanged over extended cosmological epochs, even as the universe expands. Moreover, we demonstrate that such situations are not fine-tuned but are actually global attractors within certain cosmological frameworks, with the universe naturally evolving toward such long-lasting periods of stasis for a wide variety of initial conditions. The existence of this kind of stasis therefore gives rise to a host of new theoretical possibilities across the entire cosmological timeline, ranging from potential implications for primordial density perturbations, dark-matter production, and structure formation all the way to early reheating, early matter-dominated eras, and even the age of the Universe.

We find that sub-GeV neutrino portal bosons that carry lepton number can condense inside a protoneutron star (newly born neutron star). These bosons are produced copiously and form a Bose-Einstein condensate for a range of as yet unconstrained coupling strengths to neutrinos. The condensate is a lepton number superfluid with transport properties that differ dramatically from those encountered in ordinary dense baryonic matter. We discuss how this phase could alter the evolution of protoneutron stars and comment on the implications for neutrino signals and nucleosynthesis.

We present an improved search for axionlike polarization oscillations in the cosmic microwave background (CMB) with observations from the Keck Array. An all-sky, temporally sinusoidal rotation of CMB polarization, equivalent to a time-variable cosmic birefringence, is an observable manifestation of a local axion field and potentially allows a CMB polarimeter to detect axionlike dark matter directly. We describe improvements to the method presented in previous work, and we demonstrate the updated method with an expanded dataset consisting of the 2012–2015 observing seasons. We set limits on the axion-photon coupling constant for mass $m$ in the range ${10}^{-23}–{10}^{-18}\mathrm{eV}$, which corresponds to oscillation periods on the order of hours to years. Our results are consistent with the background model. For periods between 1 and 30 d ($1.6\times {10}^{-21}\le m\le 4.8\times {10}^{-20}\mathrm{eV}$), the 95%-confidence upper limits on rotation amplitude are approximately constant with a median of 0.27°, which constrains the axion-photon coupling constant to $g_{\varphi \gamma }<(4.5\times {10}^{-12}{\mathrm{GeV}}^{-1})m/({10}^{-21}\mathrm{eV})$, if axionlike particles constitute all of the dark matter. More than half of the collected BICEP dataset has yet to be analyzed, and several current and future CMB polarimetry experiments can apply the methods presented here to achieve comparable or superior constraints. In the coming years, oscillation measurements can achieve the sensitivity to rule out unexplored regions of the axion parameter space.

Within the nonrelativistic quantum chromodynamics framework, we make a comprehensive study of the exclusive production of excited charmonium and bottomonium in $e^{+}{e}^{-}\to {\gamma }^{*}/Z^0\to |(Q\overline{Q})[n]⟩+\gamma$ ($Q=c$ or $b$ quarks) at a future $Z$ factory, where the [$n$] represents the color-singlet $n{{}^{1}S}_0$, $n{{}^{3}S}_1$, $n{{}^{1}P}_0$, and $n{{}^{3}P}_J$ ($n=1$, 2, 3, 4; $J=0$, 1, 2) Fock states. The “improved trace technology” is adopted to derive the analytic expressions at the amplitude level, which is useful for calculating the complicated $nP$-wave channels. Total cross sections, differential distributions, and uncertainties are discussed in system. According to our study, production rates of heavy quarkonia of high excited Fock states are considerable at a future $Z$ factory. The cross sections of charmonium for $2S$-, $3S$-, $4S$-, $1P$-, $2P$-, $3P$-, and $4P$-wave states are about 53.5%, 30.4%, 23.7%, 13.7%, 6.8%, 9.2%, and 9.2% of that of the $1S$ state, respectively. And cross sections of bottomonium for $2S$-, $3S$-, $4S$-, $1P$-, $2P$-, $3P$-, and $4P$-wave states are about 39.3%, 12.3%, 14.3%, 7.1%, 3.1%, 2.7%, and 3.1% of that of the $1S$ state, respectively. The main uncertainties come from the radial wave functions at the origin and their derivatives at the origin under different potential models. Then, this super $Z$ factory should be a good platform to study the properties of the high excited charmonium and bottomonium states.

We study the effective dynamics of two mirrors, forming an optical cavity, and interacting with the cavity field via radiation pressure. We pursue a perturbative influence functional approach to trace out the degrees of freedom of the field, and obtain the second-order effective action for the system composed by the mirrors. We find that the interaction between the mirrors is mediated by pairs of field modes, which combine in such a way to give rise to two different interaction channels. We find that the quantum and thermal fluctuations of the cavity field result in colored, Gaussian stochastic noises acting on the mirrors. To each of these noises is associated a dissipative effect, and the corresponding power spectra and susceptibilities are related via generalized fluctuation-dissipation relations. We finally demonstrate that the dynamics of the mirrors admits a stochastic interpretation, and give the relative quantum Langevin equations.

We investigate the feasibility of a high statistics experiment to search for invisible decay modes in nuclear gamma cascades using 200 kg of Cs(Tl) scintillators that are presently available at Texas A&M. The experiment aims to search for missing energy by robustly establishing the absence of a photon in a well-identified gamma cascade. We report on the experimental demonstration of the energy resolution necessary for this search. Prior explorations of this detector concept focused on baryonically coupled physics that could be emitted in $E_2$ transitions. We point out that this protocol can also search for particles that are coupled to photons by searching for the conversion of a photon produced in a gamma cascade into a hidden particle. Examples of these processes include the oscillation of a photon into a hidden photon and the conversion of a photon into an axionlike particle either in the presence of a magnetic field or via the Primakoff process. This proof of concept apparatus appears to have the ability to search for hitherto unconstrained baryonically coupled scalars and pseudoscalars produced in $E_0$ and $M_0$ transitions. If successfully implemented, this experiment serves as a pathfinder for a larger detector with greater containment that can thoroughly probe the existence of new particles with mass below 4 MeV that lie in the poorly constrained supernova “trapping window” that exists between 100 keV and 30 MeV.

The complex Langevin method, a numerical method used to compute the ensemble average with a complex partition function, often suffers from runaway instability. We study the regularization of the complex Langevin method via augmenting the action with a stabilization term. Since the regularization introduces biases to the numerical result, two approaches, named $2R$ and $3R$ methods, are introduced to recover the unbiased result. The $2R$ method supplements the regularization with regression to estimate the unregularized ensemble average, and the $3R$ method reduces the computational cost by coupling the regularization with a reweighting strategy before regression. Both methods can be generalized to the $SU(n)$ theory and are assessed from several perspectives. Several numerical experiments in the lattice field theory are carried out to show the effectiveness of our approaches.

In this work, we investigate the next-to-leading order (NLO) QCD correction to $J/\psi$ associated production with a bottom quark pair from the Higgs boson decay within the nonrelativistic QCD framework. From numerical results, we find that the decay width of process $H\to b+J/\psi +\overline{b}$ at leading order (LO) mainly comes from the contribution of the Fock state ${{}^{3}S}_1^{(8)}$, and the NLO QCD corrections significantly enhance the decay width at LO accuracy by about two times. At NLO accuracy, the Fock states ${{}^{3}S}_1^{(8)}$ and ${{}^{3}P}_J^{(8)}$ channels give the main contribution, accounting for about 68% and 29% of the total decay width of $J/\psi$ associated production with a bottom quark pair at NLO accuracy from the Higgs boson decay, respectively. Considering the dominant contribution of color octet (CO) channels at NLO accuracy, the inclusive decay process $H\to b+J/\psi +\overline{b}+X$ has the potential to be found in future colliders with high energy/luminosity. The study of $J/\psi$ associated production with a bottom quark pair from the Higgs boson decay is not only useful to study the mechanism of color-octet, but also to assist in the investigation of the coupling for the Higgs boson with the bottom quark.

We employ an effective kinetic description, based on the Boltzmann equation in the relaxation time approximation, to study the space-time dynamics and development of transverse flow of small and large collision systems. By combining analytical insights in the small opacity limit with numerical simulations at larger opacities, we are able to describe the development of transverse flow from very small to very large opacities. Surprisingly, we find that deviations between kinetic theory and hydrodynamics persist even in the limit of very large opacities, which can be attributed to the presence of the early preequilibrium phase.

Stimulated by the meson-baryon molecular interpretations of the $P_c$ states [$P_c(4312)/P_c(4440)/P_c(4457)$], we systematically study the interactions between an $S$-wave charm-strange baryon ${\mathrm{\Xi }}_c^{(\prime ,*)}$ and an anticharmed meson ${\overline{D}}^{(*)}$ in a coupled channel analysis. Effective potentials for the ${\mathrm{\Xi }}_c^{(\prime ,*)}{\overline{D}}^{(*)}$ interactions in a one-boson-exchange model can be related to those in the ${\mathrm{\Sigma }}_c^{(*)}{\overline{D}}^{(*)}$ systems by using the $SU(3)$ flavor symmetry and heavy quark symmetry. Our results can predict several promising hidden-charm molecular pentaquarks with strangeness $|S|=1$, which include the ${\mathrm{\Xi }}_c^{\prime }\overline{D}$ states with $I(J^P)=0,1(1/2^{-})$, the ${\mathrm{\Xi }}_c^{*}\overline{D}$ states with $0,1(3/2^{-})$, the ${\mathrm{\Xi }}_c^{\prime }{\overline{D}}^{*}$ states with $0(1/2^{-})$ and $0,1(3/2^{-})$, and the ${\mathrm{\Xi }}_c^{*}{\overline{D}}^{*}$ states with $0(1/2^{-},3/2^{-},5/2^{-})$.

The Noether currents are derived in a generic metric-affine theory of gravity, and the holographic nature of the gravitational entropy and energy-momentum is clarified. The main result is the verification of the canonical resolution to the energy-momentum problem in the Noether formalism.

Using the imaginary time formalism in thermal field theory, we derive the running coupling constant and running mass in two loop order. In the process, we express the imaginary time formalism of Feynman diagrams as the summation of nonthermal quantum field theory (QFT) Feynman diagrams with coefficients that depend on temperature and mass. Renormalization constants for thermal ${\varphi }^4$ theory were derived using simple diagrammatic analysis. Our model links the nonthermal QFT and the imaginary time formalism by assuming both have the same mass scale $\mu$ and coupling constant $g$. When these results are combined with the renormalization group equations and applied simultaneously to thermal and nonthermal proper vertex functions, the coupling constant and running mass with implicit temperature dependence are obtained. We evaluated pressure for scalar particles in two loop orders at the zero external momentum limit by substituting the running mass result in the quasiparticle model.