We find new limits on the nine ${\lambda }_{3jk}^{\prime }$ $R$-parity violating couplings of the minimal supersymmetric standard model, using Drell-Yan differential cross sections at the LHC and electroweak precision measurements from LEP and SLC. Specifically, limits on six of the nine ${\lambda }_{3jk}^{\prime }$-couplings, with $j=1$ or 2, are obtained using Drell-Yan data, providing the strongest bounds on three of these couplings. Four of the nine couplings are currently best constrained by electroweak data, which we reexamine here using a specifically lepton flavor-violating observable. The remaining two couplings are best constrained due to their contributions to neutrino masses, a bound which we update here. We also update previous limits on all ${\lambda }_{ijk}^{\prime }$-couplings using both electroweak data and neutrino mass bounds. A table of all current bounds on ${\lambda }_{ijk}^{\prime }$ is given in the Appendix.

String bit systems exhibit a Hagedorn transition in the $N\to \infty$ limit. However, there is no phase transition when $N$ is finite (but still large). We calculate two-loop, finite $N$ corrections to the partition function in the low-temperature regime. The Haar measure in the singlet-restricted partition function contributes pieces to loop corrections that diverge as $\mathcal{O}(N)$ when summed over the mode numbers. We study how these divergent pieces cancel each other out when combined. The properly normalized two-loop corrections vanish as $\mathcal{O}(N^{-1})$ for all temperatures below the Hagedorn temperature. The coefficient of this $1/N$ dependence decreases with temperature and diverges at the Hagedorn pole.

Axionlike particle (ALP)–photon couplings are modeled in large ensembles of string vacua and random matrix theories. In all cases, the effective coupling increases polynomially in the number of ALPs, of which hundreds or thousands are expected in the string ensembles, many of which are ultralight. The expected value of the couplings $g_{a\gamma \gamma }\simeq {10}^{-12}{\mathrm{GeV}}^{-1}-{10}^{-10}{\mathrm{GeV}}^{-1}$ provide viable targets for future x-ray telescopes and axion helioscopes, and in some cases are already in tension with existing data.

We compute the gravitational wave energy $E_{\mathrm{rad}}$ radiated in head-on collisions of equal-mass, nonspinning black holes in up to ($D=8$)-dimensional asymptotically flat spacetimes for boost velocities $v$ up to about 90% of the speed of light. We identify two main regimes: weak radiation at velocities up to about 40% of the speed of light, and exponential growth of $E_{\mathrm{rad}}$ with $v$ at larger velocities. Extrapolation to the speed of light predicts a limit of 12.9% (10.1, 7.7, 5.5, 4.5)% of the total mass that is lost in gravitational waves in $D=4$ (5, 6, 7, 8) spacetime dimensions. In agreement with perturbative calculations, we observe that the radiation is minimal for small but finite velocities, rather than for collisions starting from rest. Our computations support the identification of regimes with super-Planckian curvature outside the black-hole horizons reported by Okawa, Nakao, and Shibata [Phys. Rev. D 83, 121501(R) (2011)].

The purpose of this article is twofold. First, we extend the results presented in [G. Crisnejo and E. Gallo, Phys. Rev. D 97, 124016 (2018)] to stationary spacetimes. Specifically, we show that the Gauss-Bonnet theorem can be applied to describe the deflection angle of light rays in plasma media in stationary spacetimes. Second, by using a correspondence between the motion of light rays in a cold nonmagnetized plasma and relativistic test massive particles we show that this technique is not only powerful to obtain the leading order behavior of the deflection angle of massive/massless particles in the weak field regime but also to obtain higher order corrections. We particularize it to a Kerr background where we compute the deflection angle for test massive particles and light rays propagating in a nonhomogeneous cold plasma by including third order corrections in the mass and spin parameters of the black hole.

Comparing to a charged anti–de Sitter (AdS) black hole in general relativity, a new interesting phase transition—the reentrant phase transition—is observed in a charged Born-Infeld-AdS black hole system. It is worth extending the study of the relationship between the photon sphere and thermodynamic phase transition (especially the reentrant phase transition) to this black hole background. Black hole systems are divided into four cases according to the number of thermodynamic critical points, with different values of the Born-Infeld parameter $b$, where the black hole systems can have no phase transition, a reentrant phase transition, or a van der Waals-like phase transition. For these different cases, we obtain the corresponding pressure-temperature phase structures and temperature-specific volume diagrams. The tiny differences between these cases are clearly displayed. Then, we calculate the radius $r_{\mathrm{ps}}$ and the minimal impact parameter $u_{\mathrm{ps}}$ of the photon sphere via the effective potential of the radial motion of photons. $r_{\mathrm{ps}}$ and $u_{\mathrm{ps}}$ are found to have different behaviors for the different cases. In particular, with the increase of $r_{\mathrm{ps}}$ or $u_{\mathrm{ps}}$ the temperature exhibits a decrease-increase-decrease-increase behavior for fixed pressure if there is a reentrant phase transition, while for fixed temperature the pressure exhibits an increase-decrease-increase-decrease behavior instead. These behaviors are quite different from that of the van der Waals-like phase transition. Near the critical point, the behavior of $r_{\mathrm{ps}}$ and $u_{\mathrm{ps}}$ for the black hole phase transitions confirms a universal critical exponent of $\frac{1}{2}$. We also find that the temperature and pressure corresponding to the extremal points of $r_{\mathrm{ps}}$ and $u_{\mathrm{ps}}$ are highly consistent with the thermodynamic metastable curve for black hole systems with different values of $b$. Furthermore, we also extend the corresponding study to higher-dimensional black holes cases. The results show that the photon sphere behaves quite differently for the van der Waals-like and reentrant phase transitions, and both phase transitions can be identified via the photon sphere.

We consider the motion of charged and spinning bodies on the symmetry axis of a non-extremal Kerr-Newman black hole. If one treats the body as a test point particle of mass, $m$, charge $q$, and spin $S$, then by dropping the body into the black hole from sufficiently near the horizon, the first order area increase, $\delta A$, of the black hole can be made arbitrarily small, i.e., the process can be done in a “reversible” manner with regard to the change of parameters of the black hole. At second order, there may be effects on the energy delivered to the black hole—quadratic in $q$ and $S$—resulting from (i) the finite size of the body and (ii) self-force corrections to the energy. Sorce and Wald have calculated these effects for a charged, non-spinning body on the symmetry axis of an uncharged Kerr black hole and showed that, when these effects are included, ${\delta }^{2}A$ also can be made arbitrarily small, i.e., this process remains reversible to second order. We consider the generalization of this process for a charged and spinning body on the symmetry axis of a Kerr-Newman black hole, where the self-force effects have not been calculated. A spinning body (with negligible extent along the spin axis) must have a mass quadrupole moment $\gtrsim S^2/m$, so at quadratic order in the spin, we must take into account quadrupole effects on the motion. After taking into account all such finite size effects, we find that the condition ${\delta }^{2}A\ge 0$ yields a nontrivial lower bound on the self-force energy, $E_{SF}$, at the horizon. In particular, for an uncharged, spinning body on the axis of a Kerr black hole of mass $M$, the net contribution of spin self-force to the energy of the body at the horizon is $E_{SF}\ge S^2/8M^3$, corresponding to an overall repulsive spin self-force. A lower bound for the self-force energy, $E_{SF}$, for a body with both charge and spin at the horizon of a Kerr-Newman black hole is given. This lower bound will be the correct formula for $E_{SF}$ if the dropping process can be done reversibly to second order.

We revisit the Polyakov loop coupled Nambu–Jona-Lasinio model that maintains the Polyakov loop dynamics in the limit of zero temperature. This is of interest for astrophysical applications in the interior of neutron stars. For this purpose we re-examine the form of the potential for the deconfinement order parameter at finite baryonic densities. Since the modification of this potential at any temperature is formally equivalent to assigning a baryonic charge to gluons, we develop a more general formulation of the present model that cures this spurious effect and is normalized to match the asymptotic behavior of the QCD equation of state given by $\mathcal{O}({\alpha }_s^2)$ and partial $\mathcal{O}({\alpha }_s^3{\ln }^2{\alpha }_s)$ perturbative results.

We study the probability for nucleation of quark matter droplets in the dense cold cores of old neutron stars induced by the presence of a self-annihilating dark matter component, $\chi$. Using a parametrized form of the equation of state for hadronic and quark phases of ordinary matter, we explore the thermodynamical conditions under which droplet formation is facilitated by the energy injection from $\chi$ self-annihilations. We obtain the droplet nucleation time as a function of the dark matter candidate mass, $m_{\chi }$. We discuss further observational consequences.

Muons and neutrinos from cosmic ray interactions in the atmosphere originate from decays of mesons in air-showers. sibyll-2.3c aims to give a precise description of hadronic interactions in the relevant phase space for conventional and prompt leptons in light of new accelerator data, including that from the LHC. sibyll is designed primarily as an event generator for use in simulation of extensive air showers. Because it has been tuned for forward physics as well as the central region, it can also be used to calculate inclusive fluxes. The purpose of this paper is to describe the use of sibyll-2.3c for calculation of fluxes of atmospheric leptons.

We study neutrino flavor oscillations in a plane gravitational wave (GW) with circular polarization. For this purpose, we use the solution of the Hamilton-Jacobi equation to get the contribution of GW to the effective Hamiltonian for the neutrino mass eigenstates. Then, considering stochastic GWs, we derive the equation for the density matrix for flavor neutrinos and analytically solve it in the two flavors approximation. The equation for the density matrix for the three neutrino flavors is also derived and solved numerically. In both cases of two and three neutrino flavors, we predict the ratios of fluxes of different flavors at a detector for cosmic neutrinos with relatively low energies owing to the interaction with such a GW background. The obtained results are compared with the recent observation of the flavor content of the astrophysical neutrino fluxes.

We present a solution to the strong $CP$ problem that relies on the horizontal gauge symmetry and $CP$ invariance in a full theory. Similar to other Nelson-Barr-type solutions, $CP$ violation in both the strong and weak sectors of the Standard Model (SM) is attributed to the condensation of complex scalars $\mathrm{\Phi }$ in the model. The model is differentiated from others in that it explains the hierarchy in the quark-Higgs Yukawa coupling in the SM based on a series of sequential breakings of the horizontal $SU(3{)}_f$ gauge symmetry. The experimental constraint $\overline{\theta }\lesssim {10}^{-10}$ requires $⟨\mathrm{\Phi }⟩\lesssim {10}^{13}–{10}^{14}\mathrm{GeV}$ (the vacuum expectation value of complex scalars) and $\lambda \lesssim {10}^{-6}$ (the scalar quartic coupling). We show that this small coupling is natural in the sense of ’t Hooft naturalness. Compared to other Nelson-Barr-type models with a $CP$-breaking scale ${\mathrm{\Lambda }}_{CP}\lesssim {10}^8\mathrm{GeV}$, our model is more advantageous in terms of consistency with thermal leptogenesis.

The $\mathbb{C}{P}^{N-1}$ sigma model at finite temperature is studied using lattice Monte Carlo simulations on $S_s^1\times S_{\tau }^1$ with circumferences $L_s$ and $L_{\tau }$, respectively, where the ratio of the circumferences is taken to be sufficiently large ($L_s/L_{\tau }\gg 1$) to approximate the model on $\mathbb{R}\times S^1$. We show that the expectation value of the Polyakov loop undergoes a deconfinement crossover as $L_{\tau }$ is decreased, where the peak of the associated susceptibility gets sharper for larger $N$. We find that the global $\mathrm{PSU}(N)=\mathrm{SU}(N)/{\mathbb{Z}}_N$ symmetry remains unbroken in different manners for small and large $L_{\tau }$, respectively: in the small $L_{\tau }$ region for finite $N$, the order parameter fluctuates extensively with its expectation value consistent with zero after taking an ensemble average, while in the large $L_{\tau }$ region the order parameter remains small with little fluctuations. We also calculate the thermal entropy and find that the degrees of freedom in the small $L_{\tau }$ regime are consistent with $N-1$ free complex scalar fields, thereby indicating a good agreement with the prediction from the large-$N$ study for small $L_{\tau }$.

We study numerically the chromoelectric-chromomagnetic asymmetry of the dimension two $A^2$ gluon condensate at $T>T_c$ in the Landau-gauge $SU(2)$ lattice gauge theory with a particular emphasis on finite-volume effects. We show that previously found so called symmetric point at which asymmetry changes sign is an artifact of the finite volume effects. We find that with increasing temperature the asymmetry decreases approaching zero value from above in agreement with the perturbative result.

Using recently derived results for one-loop hadronic splitting functions from a nonlocal implementation of chiral effective theory, we study the contributions from pseudoscalar meson loops to flavor asymmetries in the proton. Constraining the parameters of the regulating functions by inclusive production of $n$, ${\mathrm{\Delta }}^{++}$, $\mathrm{\Lambda }$, and ${\mathrm{\Sigma }}^{*+}$ baryons in $pp$ collisions, we compute the shape of the light antiquark asymmetry $\overline{d}-\overline{u}$ in the proton and the strange asymmetry $s-\overline{s}$ in the nucleon sea. With these constraints, the magnitude of the $\overline{d}-\overline{u}$ asymmetry is found to be compatible with that extracted from the Fermilab E866 Drell-Yan measurement, with no indication of a sign change at large values of $x$, and an integrated value in the range $⟨\overline{d}-\overline{u}⟩\approx 0.09–0.17$. The $s-\overline{s}$ asymmetry is predicted to be positive at $x>0$, with compensating negative contributions at $x=0$, and an integrated $x$-weighted moment in the range $⟨x(s-\overline{s})⟩\approx (0.9-2.5)\times {10}^{-3}$.

By describing the $X(3872)$ using the extended Friedrichs scheme, in which $D{\overline{D}}^{*}$ is considered as the dominant component, we calculate the decay rates of the $X(3872)$ to ${\pi }^0$ and a $P$-wave charmonium ${\chi }_{cJ}$ state with $J=0$, 1, or 2, and the rate of its decay to $J/\psi {\pi }^{+}{\pi }^{-}$ with the help of the Barnes-Swanson model, where ${\pi }^{+}{\pi }^{-}$ are assumed to be produced via an intermediate $\rho$ state. This calculation shows that the decay rate of $X(3872)$ to ${\chi }_{c1}{\pi }^0$ is 1 order of magnitude smaller than its decay rate to $J/\psi {\pi }^{+}{\pi }^{-}$ and the decay widths of $X(3872)\to {\chi }_{cJ}{\pi }^0$ for $J=0$, 1, 2 are of the same order.

The claim that the $X(3872)$ meson cannot be a charm-meson molecule because its prompt production cross section at hadron colliders is too large is based on an upper bound in terms of a cross section for producing charm-meson pairs. Assuming $X$ is sufficiently weakly bound, we derive an equality between the $X$ cross section and a charm-meson pair cross section that takes into account the threshold enhancement from the $X$ resonance. The cross section for producing $X$ is equal to that for producing $D^{*0}{\overline{D}}^0$ integrated up to a relative momentum $k_{\max }=7.7{\gamma }_X$, where ${\gamma }_X$ is the binding momentum of $X$. We also derive an order-of-magnitude estimate of the $X$ cross section in terms of a naive charm-meson pair cross section that does not take into account the threshold enhancement, such as that produced by a Monte Carlo event generator. The cross section for producing $X$ can be approximated by the naive cross section for producing $D^{*0}{\overline{D}}^0$ integrated up to a relative momentum $k_{\max }$ of order $(m_{\pi }^2{\gamma }_X{)}^{1/3}$. The estimates of the prompt $X$ cross section at hadron colliders are consistent with the cross sections observed at the Tevatron and the LHC.

To obtain deeper understanding of QCD properties at finite temperature, we consider the Fourier decomposition of the grand-canonical partition function based on the canonical ensemble method via the imaginary chemical potential. Expectation values are, then, represented by summation over each canonical sector. We point out that the modified Polyakov loop can play an important role in the canonical ensemble; for example, the Polyakov-loop paradox which is known in the canonical ensemble method can be evaded by considering the quantity. In addition, based on the periodicity issue of the modified Polyakov loop at finite imaginary chemical potential, we can construct the systematic way to compute the dual quark condensate which has strong unclearness in its foundation in the presence of dynamical quarks so far.

Motivated by the boost-invariant Glasma state in the initial stages in heavy-ion collisions, we perform classical-statistical simulations of SU(2) gauge theory in $2+1$ dimensional space-time both with and without a scalar field in the adjoint representation. We show that irrespective of the details of the initial condition, the far-from-equilibrium evolution of these highly occupied systems approaches a unique universal attractor at high momenta that is the same for the gauge and scalar sectors. We extract the scaling exponents and the form of the distribution function close to this nonthermal fixed point. We find that the dynamics are governed by an energy cascade to higher momenta with scaling exponents $\alpha =3\beta$ and $\beta =-1/5$. We argue that these values can be obtained from parametric estimates within kinetic theory indicating the dominance of small momentum transfer in the scattering processes. We also extract the Debye mass nonperturbatively from a longitudinally polarized correlator and observe an IR enhancement of the scalar correlation function for low momenta below the Debye mass.