Scotogenic models constitute an appealing solution to the generation of neutrino masses and to the dark matter mystery. In this work we consider a version of the scotogenic model that breaks the lepton number spontaneously. At this scope, we extend the particle content of the scotogenic model with an additional singlet scalar which acquires a nonzero vacuum expectation value and breaks a global lepton number symmetry. As a consequence, a massless Goldstone boson, the majoron, appears in the particle spectrum. We discuss how the presence of the majoron modifies the phenomenology, both in flavor and dark matter observables. We focus on the fermionic dark matter candidate and analyze its relic abundance and prospects for both direct and indirect detection.

A calculation of the one-loop contribution to the rare three-body flavor changing neutral current top quark decay $t\to c\gamma \gamma$ is presented in the framework of models with one or more scalar leptoquark (LQ) $SU(2)$ doublets with hypercharge $7/6$. Analytical expressions for the invariant amplitude of the generic decay $f_i\to f_j\gamma \gamma$, with $f_{i,j}$ a lepton or quark, are presented in terms of Passarino-Veltman integral coefficients, from which the amplitudes for the processes $t\to c\gamma \gamma$ and ${\ell }_i\to {\ell }_j\gamma \gamma$ follow easily. An analysis of the current constraints on the parameter space is presented in the scenario with only one scalar LQ doublet, and bounds on the LQ couplings are obtained from the muon $g-2$ anomaly, the lepton flavor violating decay $\tau \to \mu \gamma$ and extra constraints meant to avoid tension between theory predictions and experimental data. For a LQ with a mass in the range of 1–1.5 TeV, the estimate $\mathrm{Br}(t\to c\gamma \gamma )\sim {10}^{-11}–{10}^{-12}$ is obtained for the largest allowed values of the LQ coupling constants, which means that this decay would be below the reach of future experimental measurements. We also consider a scenario with three scalar doublets, which was recently proposed to explain the lepton flavor universality violation anomalies in $B$ decays as well as the muon $g-2$ anomaly. Although this scenario allows large LQ couplings to the tau lepton and the $c$ and $t$ quarks, the branching ratio of the $t\to c\gamma \gamma$ decay is also of the order of ${10}^{-11}–{10}^{-12}$ for LQ masses of the order of 1.7 TeV.

We study relativistic corrections to exclusive $S$-wave charmonium decays into $\rho \pi$ and $\gamma \pi$ final states. The contribution of relative order $v^2$ and the set of associated higher-order corrections are calculated using nonrelativistic QCD and collinear factorization framework. Numerical estimates show that the dominant effect is provided by the corrections of relative order $v^2$. The numerical values of these contributions are of the same order as the leading-order ones. These results suggest a scenario where the sum of relativistic and radiative QCD corrections could explain the $\rho \pi$-puzzle.

We present an operator solution of the Thirring-Wess model, formulated and quantized in terms of light-front (LF) variables. The model describes a system of massless fermions interacting with massive vector bosons in two space-time dimensions. An important ingredient of the solution is a consistent quantization of the two-dimensional massless LF fermion field. The field equations are solved exactly on an operator level and the quantum LF Hamiltonian is derived in terms of independent field variables. The axial anomaly and the interacting correlation functions are computed nonperturbatively from the operator solution. An analogous operator solution in the conventional field theory is briefly described for comparison. While in the LF case the “empty” Fock vacuum is the lowest-energy eigenstate of the full Hamiltonian, the corresponding Hamiltonian in the conventional theory has to be diagonalized in order to find the true physical ground state, which is a dynamical state with a complicated structure. A comment concerning a recently discussed equivalence between the LF and conventional form of field theory concludes the paper.

We consider two initially entangled Unruh-DeWitt particle detectors and examine how the initial entanglement changes after interacting with a quantum scalar field. Just as initially separable detectors can extract entanglement from the field, entangled detectors also can gain more entanglement so long as they are weakly correlated at the beginning. For initially sufficiently entangled detectors, only degradation takes place. We then apply our analysis to a gravitational shock wave spacetime and show that a shock wave can enhance the initial entanglement of weakly entangled detectors. Moreover, we find that this enhancement can occur for greater detector separations than in Minkowski spacetime.

We revisit the thermodynamic description of fluid, represented by scalar field in scalar-tensor gravity theory through a general approach to study the thermodynamics of relativistic fluids. In order to identify the fluid energy-momentum tensor, contrary to the existing way, we use an equivalent description of gravitational dynamics both in Jordan and Einstein frames as a thermodynamical identity and fluid equation on a generic null surface. Such an approach provides the energy-momentum tensors for scalar fluid as that of an ideal fluid in both the frames. We then mention few issues in the existing way of using Eckart’s formalism for an ideal fluid. Our investigation suggests that the Eckart’s frame may not be suitable to consider an ideal fluid. Consequently a possible alternative description, valid in something other than Eckart’s frame, is being suggested for a general ideal fluid. Based on this we obtain a unified thermodynamic description in both Jordan and Einstein frames from our identified energy-momentum tensors. Finally, the relations between thermodynamic entities on different frames are being put forwarded. Thus, the description in either of the frames is enough to provide the complete picture.

The nonlinear classical graviton solution of the Einstein equations is given to second order in the null surface formulation (NSF). We solve the NSF field equations in a perturbative scheme that gives geometrical and finite results at each order of the expansion obtaining the main variables of the formalism to second order. Then, using an algebraic relationship with the NSF variables, we obtain the metric components and the nonlinear scattering of incoming gravitons. We also analyze the relevance of this result at a classical and quantum level.

We study the parity-breaking higher-curvature gravity theory of Chern-Simons (CS), using the Palatini formulation in which the metric and connection are taken to be independent fields. We first show that Palatini-CS gravity leads to first-order derivative equations of motion and thus avoid the typical instabilities of CS gravity in the metric formalism. As an initial application, we analyze the cosmological propagation of gravitational waves (GWs) in Palatini-CS gravity. We show that, due to parity breaking, the polarizations of GWs suffer two effects during propagation: amplitude birefringence (which changes the polarization ellipticity) and velocity birefringence (which rotates the polarization plane). While amplitude birefringence is known to be present in CS gravity in the metric formalism, velocity birefringence is not present in metric CS gravity for high frequency waves, but now appears in Palatini-CS due to the fact that left-handed and right-handed GW polarizations have a different dispersion relation. In the approximation of small deviations from general relativity (GR), we do find however that velocity birefringence appears at least quadratically in the CS coupling parameter $\alpha$, while amplitude birefringence appears linearly in $\alpha$. This means that amplitude birefringence will be the most relevant effect in Palatini-CS and hence this model will behave similarly to metric CS. We confirm this by applying current constraints on amplitude and velocity birefringence to Palatini-CS, and showing that those from amplitude birefringence give the tightest bounds.

We consider a model of baryogenesis based on adding lepton number-violating quadratic mass terms to the inflaton potential of a nonminimally coupled inflation model. The $L$-violating mass terms generate a lepton asymmetry in a complex inflaton field via the mass term Affleck-Dine mechanism, which is transferred to the Standard Model (SM) sector when the inflaton decays to right-handed (RH) neutrinos. The model is minimal in that it requires only the SM sector, RH neutrinos, and a nonminimally coupled inflaton sector. We find that baryon isocurvature fluctuations can be observable in metric inflation but are negligible in Palatini inflation. The model is compatible with reheating temperatures that may be detectable in the observable primordial gravitational waves predicted by metric inflation.

The separable analytical solution in standard perturbation theory for an Einstein–de Sitter (EdS) universe can be generalized to the wider class of such cosmologies (“generalized EdS,” or gEdS) in which a fraction of the pressureless fluid does not cluster. We derive the corresponding kernels in both Eulerian perturbation theory (EPT) and Lagrangian perturbation theory, generalizing the canonical EdS expressions to a one-parameter family where the parameter can be taken to be the exponent $\alpha$ of the growing mode linear amplification $D(a)\propto a^{\alpha }$. For the power spectrum (PS) at one loop in EPT, the contribution additional to standard EdS is given, for each of the “13” and “22” terms, as a function of two infrared safe integrals. In the second part of the paper we show that the calculation of cosmology-dependent corrections in perturbation theory in standard [e.g., Lambda cold dark matter (LCDM)] models can be simplified, and their magnitude and parameter dependence better understood, by relating them to our analytic results for gEdS models. At second order the time dependent kernels are equivalent to the analytic kernels of the gEdS model with $\alpha$ replaced by a single redshift dependent effective growth rate ${\alpha }_2(z)$. At third order the time evolution can be conveniently parametrized in terms of two additional such effective growth rates. For the PS calculated at one-loop order, the correction to the PS relative to the EdS limit can be expressed in terms of just ${\alpha }_2(z)$, one additional effective growth rate function, and the four infrared safe integrals of the gEdS limit. This is much simplified compared to expressions in the literature that use six or eight redshift dependent functions and are not explicitly infrared safe. Using the analytic gEdS expression for the PS with $\alpha ={\alpha }_2(z)$ gives a good approximation (to $\sim 25\%$) for the exact result.

Neutrino-neutrino forward scatterings potentially induce collective neutrino oscillation in dense neutrino gases in astrophysical sites such as core-collapse supernovae (CCSNe) and binary neutron star mergers (BNSMs). In this paper, we present a detailed study of fast neutrino-flavor conversion (FFC), paying special attention to asymptotic states, by means of stability analysis and local simulations with a periodic boundary condition. We find that asymptotic states can be characterized by two key properties of FFC: (1) the conservation of lepton number for each flavor of neutrinos and (2) the disappearance of ELN (electron neutrino-lepton number)-XLN (heavy-leptonic one) angular crossings in the spatial- or time-averaged distributions. The system that initially has the positive (negative) ELN-XLN density reaches a flavor equipartition in the negative (positive) ELN-XLN angular directions, and the other part compensates it to preserve the conservation laws. These properties of FFCs offer an approximate scheme determining the survival probability of neutrinos in asymptotic states without solving quantum kinetic equations. We also demonstrate that the total amount of flavor conversion can vary with species-dependent neutrino distributions for identical ELN-XLN ones. Our results suggest that even shallow or narrow ELN angular crossings have the ability to shuffle large amount of neutrinos among flavors through FFC in the angular directions where neutrinos are more abundant, indicating the need for including the effects of FFCs in the modeling of CCSN and BNSM.

Pulsars are considered to be the leading explanation for the excess in cosmic-ray positrons. A notable feature of standard pulsar models is the sharp spectral cutoff produced by the increasingly efficient cooling of very-high-energy electrons by synchrotron and inverse-Compton processes. This spectral break has been used to argue that many pulsars contribute to the positron flux and that spectral features cannot distinguish between dark matter and pulsar models. We prove that this feature does not exist—it appears due to approximations that treat inverse-Compton scattering as a continuous, instead of as a discrete and catastrophic, energy-loss process. Astrophysical sources do not produce sharp spectral features via cooling, reopening the possibility that such a feature would provide evidence for dark matter.

The Galactic center $\gamma$-ray excess, detected by the Fermi-LAT, is a very attractive tentative signal from dark matter annihilation. Searching for associated synchrotron emissions can test the dark matter interpretation for this excess. We geared the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) toward Coma Berenices (a dwarf spheroidal galaxy) for two hours of observation, and found no significant continuum radio emission, which could put constraints on the dark matter annihilation cross section, from our target. We set very stringent annihilation cross section constraints, with roughly an order of magnitude improvement over a large range of masses compared with previous radio searches. The dark matter scenario for the Galactic center $\gamma$-ray excess is in tension with the FAST observation for reasonable choices of astrophysical factors. But considering the large uncertainty on astrophysical parameters, such as the magnetic field, the diffusion coefficient, and the diffusion radius, and on dark matter halo parameters, the dark matter interpretation for the excess could still survive. Further radio observations by the FAST and other radio telescopes may reveal more about the dark matter properties.

The $\tau$ polarization in semileptonic $B$ decays provides probes of new physics complementary to decay rate distributions of the three-body final state. Prior calculations for inclusive decays used a definition for the polarization axis that is different from the choice used in calculations (and the only measurement) for exclusive channels. To compare inclusive and exclusive predictions, we calculate the $\tau$ polarization in inclusive $B\to X\tau \overline{\nu }$ using the same choice as in the exclusive decays, and construct a sum rule relating the inclusive $\tau$ polarization to a weighted sum of exclusive decay polarizations. We use this relation, experimental data, and theoretical predictions for the decays to the lightest charm or up-type hadrons to make predictions for excited channels.

Models with an axionlike particle (ALP) can provide an explanation for the discrepancy between experimental measurement of the muon anomalous-magnetic moment $(g-2{)}_{\mu }$ and the Standard Model prediction. This explanation relies on the couplings of the ALP to the muon and the photon. We also include more general couplings to the electroweak gauge bosons and incorporate them in the calculations up to the 2-loop order. We investigate the existing experimental constraints and find that they do not rule out the ALP model under consideration as a possible explanation for the $(g-2{)}_{\mu }$ anomaly. At the same time, we find the future Tera-$Z$ and Higgs factories, such as the CEPC and FCC-ee, can completely cover the relevant parameter space through searches with final states $(\gamma \gamma )\gamma$, $({\mu }^{+}{\mu }^{-})\gamma$, and $({\mu }^{+}{\mu }^{-}){\mu }^{+}{\mu }^{-}$.

We derive covariant equations describing the tetraquark in terms of an admixture of two-body states $D\overline{D}$ (diquark-antidiquark), $MM$ (meson-meson), and three-body-like states $q\overline{q}(T_{q\overline{q}})$, $qq(T_{\overline{q}\overline{q}})$, and $\overline{q}\overline{q}(T_{qq})$ where two of the quarks are spectators while the other two are interacting (their t matrices denoted correspondingly as $T_{q\overline{q}}$, $T_{\overline{q}\overline{q}}$, and $T_{qq}$). This has been achieved by describing the $qq\overline{q}\overline{q}$ system using the Faddeev-like four-body equations of Khvedelidze and Kvinikhidze [Theor. Math. Phys. 90, 62 (1992)] while retaining all two-body interactions (in contrast to previous works where terms involving isolated two-quark scattering were neglected). As such, our formulation, is able to unify seemingly unrelated models of the tetraquark, like, for example, the $D\overline{D}$ model of the Moscow group [Faustov et al., Universe 7, 94 (2021)] and the coupled channel $D\overline{D}-MM$ model of the Giessen group [Heupel et al., Phys. Lett. B 718, 545 (2012)].

We evaluate the full opacity dependence of collective flow in high-energy heavy-ion collisions within a microscopic kinetic description based on the Boltzmann equation in the conformal relaxation time approximation. By comparing kinetic theory calculations to hydrodynamic and hybrid simulations for an average initial state, we point out shortcomings and inaccuracies of hydrodynamic models and present modified simulation setups to improve them.

We calculate the weak transition form factors of the ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }(1520)$ transition, and further calculate the angular distributions of the rare decays ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }(1520)(\to N\overline{K}){\ell }^{+}{\ell }^{-}$ ($N\overline{K}=\{p{K}^{-},n{\overline{K}}^0\}$) with unpolarized ${\mathrm{\Lambda }}_b$ and massive leptons. The form factors are calculated by the three-body light-front quark model with the support of numerical wave functions of ${\mathrm{\Lambda }}_b$ and $\mathrm{\Lambda }(1520)$ from solving the semirelativistic potential model associated with the Gaussian expansion method. By fitting the mass spectrum of the observed single bottom and charmed baryons, the parameters of the potential model are fixed, so this strategy can avoid the uncertainties arising from the choice of a simple harmonic oscillator wave function of the baryons. With more data accumulated in the LHCb experiment, our result can help for exploring the ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }(1520){\ell }^{+}{\ell }^{-}$ decay and deepen our understanding on the $b\to s{\ell }^{+}{\ell }^{-}$ processes.

We investigate the sensitivity of a large underground Liquid Argon Time Projection Chamber (LArTPC)-based neutrino detector to dark matter in the Galactic Center annihilating into neutrinos. Such a detector could have the ability to resolve the direction of the electron in a neutrino scattering event and thus to infer information about the source direction for individual neutrino events. We consider the improvements on the expected experimental sensitivity that this directional information would provide. Even without directional information, we find a DUNE-like LArTPC detector is capable of setting limits on dark matter annihilation to neutrinos for dark matter masses above 30 MeV that are competitive with or exceed current experimental reach. While currently-demonstrated angular resolution for low-energy electrons is insufficient to allow any significant increase in sensitivity, these techniques could benefit from improvements to algorithms and the additional spatial information provided by novel 3D charge imaging approaches. We consider the impact of such enhancements to the resolution for electron directionality and find that, where electron-scattering events can be distinguished from charged-current neutrino interactions, limits on dark matter annihilation in the mass range where solar neutrino backgrounds dominate ($\lesssim 15\mathrm{MeV}$) can be significantly improved using directional information, and would be competitive with existing limits using $40\mathrm{kton}\times \mathrm{year}$ of exposure.

We study the topology of black hole thermodynamics in four-, five-, and seven-dimensional $R$-charged black holes. While the 4D $R$-charged black hole possesses four charges, the 5D and 7D $R$-charged black holes have three and two charges, respectively. In our study, we investigate the influence of charge configuration of the $R$-charged black holes on the topology of their thermodynamics. In each of these black holes, we consider a number of different charge configurations and compute the topological charges associated with the critical points. Based on the values of the topological charges, we classify the critical points into conventional and novel critical points. We find that the number of critical points and their nature depends on the charge configuration of the $R$-charged black holes irrespective of their dimensionality. However, the total topological charge for all the charge configurations in 4D, 5D, and 7D remains the same, $Q=-1$. This indicates that the $R$-charged black holes in 4D, 5D, and 7D are thermodynamically in the same topological class. We also conclude that the variation of charge configurations does not have any impact on the topological class of thermodynamics for $R$-charged black holes.