We calculate the tree-level mass spectrum for a linear sigma model describing the scalar and pseudoscalar mesons of a $SU(3)$ local gauge theory with Dirac fermions in the fundamental representation. $N_1$ fermions have a mass $m_1$ and $N_2$ a mass $m_2$. Using recent lattice data with $m_1=m_2$ and $N_1+N_2=8$ or 12, we predict the mass splittings for $m_2=m_1+\delta m$. At first order in $\delta m$, an interesting inverted pattern appears in the $0^{++}$ sector, where mesons with lighter fermions are heavier. This feature could be tested in ongoing calculations provided that $m_1$ and $\delta m$ are sufficiently small. We discuss possible improvements of the approach.

We present here the first result on the three-loop gluon jet function in perturbative QCD. Using the three-loop coefficient functions [J. A. M. Vermaseren, A. Vogt, and S. Moch, Nucl. Phys. B724, 3 (2005)., G. Soar, S. Moch, J. A. M. Vermaseren, and A. Vogt, Nucl. Phys. B832, 152 (2010).] for deep-inelastic scattering via the exchange of a virtual photon that couples to quarks or a scalar that couples to gluons and employing the KG equation, renormalization group invariance and factorization theorem, we obtain both the quark and the gluon jet functions up to the three-loop level. The former agrees with the recent result [R. Brüser, Z. L. Liu, and M. Stahlhofen, Phys. Rev. Lett. 121, 072003 (2018).]. These jet functions being universal ingredients in the SCET framework, will play an important role in the phenomenological studies at the Large Hadron Collider, such as resummation of jet observables and also in N-jettiness subtraction method.

We calculate the spectrum of $q\overline{q}c\overline{c}$ and $s\overline{s}c\overline{c}$ tetraquarks, where $q$, $s$, and $c$ stand for light ($u$, $d$), strange, and charm quarks, respectively, in a relativized diquark model, characterized by one-gluon-exchange plus confining potential. In the diquark model, a $q\overline{q}c\overline{c}$ ($s\overline{s}c\overline{c}$) tetraquark configuration is made up of a heavy-light diquark, $qc$ ($sc$), and anti-diquark, $\overline{q}\overline{c}$ ($\overline{s}\overline{c}$). According to our results, 13 charmonium-like observed states can be accommodated in the tetraquark picture, both in the hidden-charm ($q\overline{q}c\overline{c}$) and hidden-charm hidden-strange ($s\overline{s}c\overline{c}$) sectors.

A search for electroweak production of supersymmetric particles is performed in two-lepton and three-lepton final states using recursive jigsaw reconstruction, a technique that assigns reconstructed objects to the most probable hemispheres of the decay trees, allowing one to construct tailored kinematic variables to separate the signal and background. The search uses data collected in 2015 and 2016 by the ATLAS experiment in $\sqrt{s}=13\mathrm{TeV}$ proton-proton collisions at the CERN Large Hadron Collider corresponding to an integrated luminosity of $36.1{\mathrm{fb}}^{-1}$. Chargino-neutralino pair production, with decays via $W/Z$ bosons, is studied in final states involving leptons and jets and missing transverse momentum for scenarios with large and intermediate mass splittings between the parent particle and lightest supersymmetric particle, as well as for the scenario where this mass splitting is close to the mass of the $Z$ boson. The latter case is challenging since the vector bosons are produced with kinematic properties that are similar to those in Standard Model processes. Results are found to be compatible with the Standard Model expectations in the signal regions targeting large and intermediate mass splittings, and chargino-neutralino masses up to 600 GeV are excluded at 95% confidence level for a massless lightest supersymmetric particle. Excesses of data above the expected background are found in the signal regions targeting low mass splittings, and the largest local excess amounts to 3.0 standard deviations.

The discovery of ${\mathrm{\Xi }}_{cc}^{++}$ by the LHCb Collaboration triggers predictions of more doubly charmed baryons. By taking into account both the $P$-wave excitations between the two charm quarks and the scattering of light pseudoscalar mesons off the ground state doubly charmed baryons, a set of negative-parity spin-$1/2$ doubly charmed baryons are predicted already from a unitarized version of leading order chiral perturbation theory. Moreover, employing heavy antiquark-diquark symmetry, the relevant low-energy constants in the next-to-leading order are connected with those describing light pseudoscalar mesons scattering off charmed mesons, which have been well determined from lattice calculations and experimental data. Our calculations result in a spectrum richer than that of heavy mesons. We find two very narrow $J^P=1/2^{-}$ ${\mathrm{\Omega }}_{cc}^P$, which very likely decay into ${\mathrm{\Omega }}_{cc}{\pi }^0$ breaking isospin symmetry. In the isospin-$1/2$ ${\mathrm{\Xi }}_{cc}^P$ sector, three states are predicted to exist below 4.2 GeV with the lowest one being narrow and the other two rather broad. We suggest to search for the ${\mathrm{\Xi }}_{cc}^P$ states in the ${\mathrm{\Xi }}_{cc}^{++}{\pi }^{-}$ mode. Searching for them and their analogues are helpful to establish the hadron spectrum.

Many discussions in the literature of spacetimes with more than one Killing horizon note that some horizons have positive and some have negative surface gravities, but assign to all a positive temperature. However, the first law of thermodynamics then takes a nonstandard form. We show that if one regards the Christodoulou and Ruffini formula for the total energy or enthalpy as defining the Gibbs surface, then the rules of Gibbsian thermodynamics imply that negative temperatures arise inevitably on inner horizons, as does the conventional form of the first law. We provide many new examples of this phenomenon, including black holes in STU supergravity. We also give a discussion of left and right temperatures and entropies, and show that both the left and right temperatures are non-negative. The left-hand sector contributes exactly half the total energy of the system, and the right-hand sector contributes the other half. Both the sectors satisfy conventional first laws and Smarr formulas. For spacetimes with a positive cosmological constant, the cosmological horizon is naturally assigned a negative Gibbsian temperature. We also explore entropy-product formulas and a novel entropy-inversion formula, and we use them to test whether the entropy is a super-additive function of the extensive variables. We find that super-additivity is typically satisfied, but we find a counterexample for dyonic Kaluza-Klein black holes.

Based on the generalized Bloch equation, the transseries expansion for the phase (exponent) of the ground state density for double-well potential is constructed. It is shown that the leading and next-to-leading terms in semiclassical expansion are still defined by the flucton trajectory (its classical action) and quadratic fluctuations (the determinant), respectively, while the next-to-next-to-leading term (at large distances) is of nonperturbative nature. It comes from the fact that all flucton classical trajectories modified by multi-instanton, instanton–anti-instanton additions lead to the same classical action behavior at large distances. This correction is proportional to sum of all leading instanton contributions to energy gap.

Equipped with new powerful and efficient methods for computing quantum expectation values in static-spherically symmetric spacetimes in arbitrary dimensions, we perform an in-depth investigation of how the quantum vacuum polarization varies with the parameters in the theory. In particular, we compute and compare the vacuum polarization for a quantum scalar field in the Schwarzschild–anti–de Sitter black hole spacetime for a range of values of the field mass and field coupling constant as well as the black hole mass and number of spacetime dimensions. In addition, a new approximation for the vacuum polarization in asymptotically anti–de Sitter black hole spacetimes is presented.

Until now, the critical behavior of Lifshitz black holes, in an extended $P-v$ space, has not been studied, because it is impossible to find an analytical equation of state, $P=P(v,T)$, for an arbitrary Lifshitz exponent $z$. In this paper, we adopt a new approach toward thermodynamic phase space and successfully explore the critical behavior of ($n+1$)-dimensional Lifshitz dilaton black holes. The most important advantage of this approach is that we keep the cosmological constant as a constant without needing to vary it. For this purpose, we write down the equation of state as $Q^s=Q^s(T,\mathrm{\Psi })$, where $\mathrm{\Psi }={(\partial M/\partial Q^s)}_{S,P}$ is the conjugate of $Q^s$, and construct a Smarr relation based on this new phase space as $M=M(S,Q^s,P)$, where $s=2p/(2p-1)$, with $p$ the power of the power-law Maxwell Lagrangian. We justify such a choice mathematically and show that with this new phase space, the system admits the critical behavior and resembles the van der Waals fluid system when the cosmological constant (pressure) is treated as a fixed parameter, while the charge of the system varies. We obtain the Gibbs free energy of the system and find a swallowtail shape in Gibbs diagrams, which represents the first-order phase transition. Finally, we calculate the critical exponents and show that although thermodynamic quantities depend on the metric parameters such as $z$, $p$, and $n$, the critical exponents are the same as the van der Waals fluid-gas system. This alternative viewpoint of the phase space of a Lifshitz dilaton black hole can be understood easily since one can imagine such a change for a given single black hole, i.e., acquiring charge, which induces the phase transition. Our results further support the viewpoint suggested in [A. Dehyadegari, A. Sheykhi, and A. Montakhab, Phys. Lett. B 768, 235 (2017)].

Gravity theories beyond general relativity (GR) can change the properties of gravitational waves: their polarizations, dispersion, speed, and, importantly, energy content are all heavily theory dependent. All these corrections can potentially be probed by measuring the stochastic gravitational-wave background. However, most existing treatments of this background beyond GR overlook modifications to the energy carried by gravitational waves, or rely on GR assumptions that are invalid in other theories. This may lead to mistranslation between the observable cross-correlation of detector outputs and gravitational-wave energy density, and thus to errors when deriving observational constraints on theories. In this article, we lay out a generic formalism for stochastic gravitational-wave searches, applicable to a large family of theories beyond GR. We explicitly state the (often tacit) assumptions that go into these searches, evaluating their generic applicability, or lack thereof. Examples of problematic assumptions are as follows: statistical independence of linear polarization amplitudes; which polarizations satisfy equipartition; and which polarizations have well-defined phase velocities. We also show how to correctly infer the value of the stochastic energy density in the context of any given theory. We demonstrate with specific theories in which some of the traditional assumptions break down: Chern-Simons gravity, scalar-tensor theory, and Fierz-Pauli massive gravity. In each theory, we show how to properly include the beyond-GR corrections, and how to interpret observational results.

We solve the $2+1$-dimensional Teukolsky equation numerically for the Weyl scalars ${\psi }_0$ and ${\psi }_4$ along a time-like geodesic approaching the Cauchy horizon of a rapidly rotating perturbed Kerr black hole. We find that both the amplitude and frequency of the Weyl scalars agree with the results of linear perturbation analysis. We then model a physical object by a simple damped harmonic oscillator, which is driven by an external force that mimics the tidal force experienced by the infalling object. We use this model to find the total deformation of the object at the Cauchy horizon, and the resonant effect when the driving force’s frequency matches the internal frequency of the oscillator that models the object.

Recently we have introduced a nonrelativistic cosmological model (NRCM) exhibiting a dynamical spatial curvature. For this model the present day cosmic acceleration is not attributed to a negative pressure (dark energy), but it is driven by a nontrivial energy flow leading to a negative spatial curvature. In this paper, we generalize the NRCM in two different ways to the relativistic regime and present analytical solutions of the corresponding Einstein equations. These relativistic models are characterized by two inequivalent extensions of the Friedmann-Lemaître-Robertson-Walker metric with a time-dependent curvature function $K(t)$ and an expansion scalar $a(t)$. The fluid flow is supposed to be geodesic. The model V1 is shear free with isotropic pressure and therefore conformally flat. It shows some common properties with the spherically symmetric Stephani models, but it exhibits also some specific differences. In contrast to V1, the second model V2 shows a nontrivial shear and an anisotropic pressure. For both models, the inhomogeneous solutions of the corresponding Einstein equations will agree in leading order at small distances with the NRCM if $a(t)$ and $K(t)$ are each identical with those determined in the NRCM. This will be achieved by the demand of vanishing isotropic pressure and its first derivative with respect to $r^2$ at the coordinate origin $r=0$. Then the metric is completely fixed by three constants. The arising energy momentum tensor contains a nontrivial energy flow vector. Our models violate locally the weak energy condition. As this may be caused by some averaging, we speculate about to view each of our models as a local average of some other more fundamental model. Global volume averaging leads to explicit expressions for the effective scale factor and the expansion rate $H(z)$. Backreaction effects cancel each other for the model V2 but they are nonzero and proportional to the square of the magnitude of the energy flow for the model V1. The large-scale (relativistic) corrections to the NRCM results are small for the model V2 for a small-sized energy flow. We have reproduced a corresponding adjustment of the three free constants from [1] to cosmic chronometer data, leading to the prediction of an almost constant, negative value for the dimensionless curvature function $k(z)\sim -1$ for redshifts $z<2$.

In three dimensions, there exist modifications of Einstein’s gravity akin to the topologically massive gravity that describe massive gravitons about maximally symmetric backgrounds. These theories are built on the three-dimensional version of the Bach tensor (a curl of the Cotton-York tensor) and its higher derivative generalizations; and they are on-shell consistent without a Lagrangian description based on the metric tensor alone. We give a generic construction of these models, find the spectra and compute the conserved quantities for the Bañados-Teitelboim-Zanelli black hole.

The observed rapid cooling of the neutron star (NS) located at the center of the supernova remnant Cassiopeia A (Cas A) can be explained in the minimal NS cooling scenario. This consequence may be changed if there exists an extra cooling source, such as axion emission. In this work, we study the Cas A NS cooling in the presence of axion emission, taking account of the temperature evolution in the whole life of the Cas A NS. We obtain a lower limit on the axion decay constant, $f_a\gtrsim (5-7)\times {10}^8\mathrm{GeV}$, if the star has an envelope with a thin carbon layer. This is as strong as existing limits imposed by other astrophysical observations such as SN1987A.

The DarkSide-50 direct-detection dark matter experiment is a dual-phase argon time projection chamber operating at Laboratori Nazionali del Gran Sasso. This paper reports on the blind analysis of a $(16660\pm 270)\mathrm{kg}\mathrm{d}$ exposure using a target of low-radioactivity argon extracted from underground sources. We find no events in the dark matter selection box and set a 90% C.L. upper limit on the dark matter–nucleon spin-independent cross section of $1.14\times {10}^{-44}{\mathrm{cm}}^2$ ($3.78\times {10}^{-44}{\mathrm{cm}}^2$, $3.43\times {10}^{-43}{\mathrm{cm}}^2$) for a WIMP mass of $100\mathrm{GeV}/c^2$ ($1\mathrm{TeV}/c^2$, $10\mathrm{TeV}/c^2$).

We perform an explicit calculation of the axial current at finite rotation and temperature in curved space. We find that finite curvature and mass corrections to the chiral vortical effect satisfy a relation of the chiral gap effect, that is, a fermion mass shift by a scalar curvature. We also point out that a product term of the angular velocity and the scalar curvature shares the same coefficient as the mixed gravitational chiral anomaly. We discuss possible applications of the curvature-induced chiral vortical effect to rotating astrophysical compact objects described by the Kerr metric. Instead of direct calculation, we assume that the Chern-Simons current can approximate the physical axial current. We make a proposal that the chiral vortical current from rotating compact objects could provide a novel microscopic mechanism behind the generation of collimated jets.

Here we discuss the description of flavor neutrinos produced or detected in processes which involve more than one neutrino. We show that in these cases flavor neutrinos cannot be separately described by pure states, but require a density matrix description. We consider explicitly the examples of ${\nu }_e$ and ${\overline{\nu }}_{\mu }$ production in ${\mu }^{+}$ decay and ${\nu }_{\mu }$ detection through scattering on electrons. We show that the density matrix which describes a flavor neutrino can be approximated with a density matrix of a pure state only when the differences of the neutrino masses are neglected in the interaction process. In this approximation, the pure states are the standard flavor states and one recovers the standard expression for the neutrino oscillation probability. We discuss also the effects of mixing of the three standard light neutrinos with heavy neutrinos which can be either decoupled because their masses are much larger than the maximum neutrino energy in the neutrino production process or because they are produced and detected incoherently. Finally, we discuss the more complicated case of neutrino-electron elastic scattering, in which the initial and final neutrinos do not have determined flavors, but there is a flavor dependence due to the different contributions of charged-current and neutral-current interactions.

The decays $D^0\to d\overline{u}{e}^{+}\nu \to a_0^{-}(980)e^{+}\nu \to {\pi }^{-}\eta e^{+}\nu$ and $D^{+}\to d\overline{d}{e}^{+}\nu \to a_0^0(980)e^{+}\nu \to {\pi }^0\eta e^{+}\nu$ (and the charge conjugated ones) are the direct probe of the constituent two-quark components in the $a_0^{\pm }(980)$ and $a_0^0(980)$ wave functions. The recent BESIII experiment is the first step in the experimental study of these decays. We suggest adequate formulas for the data analysis and present a variant of $\eta \pi$ invariant mass distribution when $a_0(980)$ has no constituent two-quark component at all.

To improve the theoretical prediction of the anomalous dipole moments of the $\tau$-neutrino, we have carried out a study through the processes $e^{+}{e}^{-}\to (\gamma ,Z)\to {\nu }_{\tau }{\overline{\nu }}_{\tau }\gamma$ and $\gamma e^{-}\to \tau {\overline{\nu }}_{\tau }{\nu }_e$, which represent an excellent and useful option in determination of these anomalous parameters. Furthermore, we consider the effective Lagrangian formalism which induces contributions to the dipole moments of the tau-neutrino. To study the potential of the processes $e^{+}{e}^{-}\to (\gamma ,Z)\to {\nu }_{\tau }{\overline{\nu }}_{\tau }\gamma$ and $\gamma e^{-}\to \tau {\overline{\nu }}_{\tau }{\nu }_e$ we apply a future high-energy and high-luminosity linear electron-positron collider, such as the CLIC, with $\sqrt{s}=380$, 1500, 3000 GeV and $\mathcal{L}=10$, 50, 100, 200, 500, 1000, 1500, 2000, $3000{\mathrm{fb}}^{-1}$, and we consider systematic uncertainties of ${\delta }_{\mathrm{sys}}=0\%$, 5%, 10%. Furthermore, we including initial state radiation plus beamstrahlung effects. With these elements, we present a comprehensive and detailed sensitivity study on the total cross section of the processes $e^{+}{e}^{-}\to (\gamma ,Z)\to {\nu }_{\tau }{\overline{\nu }}_{\tau }\gamma$ and $\gamma e^{-}\to \tau {\overline{\nu }}_{\tau }{\nu }_e$, as well as on the dipole moments ${\tilde{\kappa }}_{{\nu }_{\tau }}$ and ${\tilde{d}}_{{\nu }_{\tau }}$ at the 95% C.L., showing the feasibility of such processes at the CLIC at the $e^{+}{e}^{-}$ and $\gamma e^{-}$ modes with unpolarized and polarized electron-positron beams.

We analyze the branching of center vortices in SU(3) Yang-Mills theory in maximal center gauge. When properly normalized, we can define a branching probability that turns out to be independent of the lattice spacing (in the limited scaling window studied here). The branching probability shows a rapid change at the deconfinement phase transition, which is much more pronounced in space slices of the lattice as compared to time slices. Though not a strict order parameter (in the sense that it vanishes in one phase) the branching probability is thus found to be a reliable indicator for both the location of the critical temperature and the geometric rearrangement of vortex matter across the deconfinement phase transition.