We determine constraints on sterile neutrino warm dark matter through direct detection experiments, taking XENON100, XENON1T, and DARWIN as examples. If keV-scale sterile neutrinos scatter inelastically with bound electrons of the target material, an electron recoil signal is generated. This can be used to set limits on the sterile neutrino mass and its mixing with the active sector. While not competitive with astrophysical constraints from x-ray data, the constraints are the first direct laboratory bounds on sterile neutrino warm dark matter and will be in some parts of parameter space the strongest limits on keV-scale neutrinos.

A model of a neutrino mixing with an $A_4\times Z_3\times Z_4$ flavor symmetry is suggested. In addition to the standard model fields, the present model contains six new fields that transform under different representations of $A_4\times Z_3\times Z_4$. The model is constructed to slightly deviate from a tribimaximal model in agreement with the current experimental data; thus, all analysis can be done in the base of the perturbation method. Within this model, as an application, a relation between the mixing angles (${\theta }_{12}$, ${\theta }_{23}$, ${\theta }_{13}$) and the Dirac $CP$-violation phase (${\delta }_{CP}$) is established. This relation allows a prediction of ${\delta }_{CP}$ and the Jarlskog parameter ($J_{CP}$). The predicted value ${\delta }_{CP}$ is in the $1\sigma$ region of the global fit for both the normal and inverse neutrino mass ordering and gives $J_{CP}$ to be within the bound $|J_{CP}|\le 0.04$. For an illustration, the model is checked numerically and gives values of the neutrino masses (of the order of 0.1 eV) and the mixing angle ${\theta }_{13}$ (about 9°) very close to the current experimental data.

We perform a detailed study of an effective field theory which includes the standard model particle content extended by a pair of Weyl fermionic SU(2) doublets with opposite hypercharges. A discrete symmetry guarantees that a linear combination of the doublet components is stable and can act as a candidate particle for dark matter. The dark sector fermions interact with the Higgs and gauge bosons through renormalizable $d=4$ operators, and nonrenormalizable $d=5$ operators that appear after integrating out extra degrees of freedom above the TeV scale. We study collider, cosmological and astrophysical probes for this effective theory of dark matter. We find that a weakly interacting dark matter particle with a mass nearby the electroweak scale, and thus observable at the LHC, is consistent with collider and astrophysical data only when fairly large magnetic dipole moment transition operators with the gauge bosons exist, together with moderate Yukawa interactions.

We explore the use of Wilson flow to study the deconfinement transition in SU(3) gauge theory. We use the flowed Polyakov loop as a renormalized order parameter for the transition, and use it to renormalize the Polyakov loop. We also study the flow properties of the electric and magnetic gluon condensates, and demonstrate that the difference of the flowed operators shows rapid change across the transition point.

We investigate the potential for measuring the $CP$ state of the Higgs boson in $H\to \tau \tau$ decays with consecutive $\tau$-lepton decays in the channels: ${\tau }^{\pm }\to {\rho }^{\pm }{\nu }_{\tau }$ and ${\tau }^{\pm }\to a_1^{\pm }{\nu }_{\tau }$ combined. Subsequent decays ${\rho }^{\pm }\to {\pi }^{\pm }{\pi }^0$, $a_1^{\pm }\to {\rho }^0{\pi }^{\pm }$ and ${\rho }^0\to {\pi }^{+}{\pi }^{-}$ are taken into account. We will explore extensions of the method, where the acoplanarity angle for the planes build on the visible decay products, ${\pi }^{\pm }{\pi }^0$ of ${\tau }^{\pm }\to {\pi }^{\pm }{\pi }^0{\nu }_{\tau }$, was used. The angle is sensitive to transverse spin correlations, thus to parity. We show that in the case of the cascade decays of $\tau \to a_1\nu$, information on the $CP$ state of Higgs can be extracted from the acoplanarity angles as well. Because in the cascade decay $a_1^{\pm }\to {\rho }^0{\pi }^{\pm }$, ${\rho }^0\to {\pi }^{+}{\pi }^{-}$ up to four planes can be defined, up to 16 distinct acoplanarity angles are available for $H\to \tau \tau \to a_1^{+}{a}_1^{-}\nu \nu$ decays. These acoplanarities carry in part supplementary but also correlated information. It is thus cumbersome to evaluate an overall sensitivity. We investigate the sensitivity potential of such analysis, by developing and applying machine learning techniques. We quantify possible improvements when multidimensional phase space of outgoing decay products directions is used, instead of one-dimensional projections i.e. the acoplanarity angles. We do not take into account ambiguities resulting from detector uncertainties or background contamination; we concentrate on the usefulness of machine learning methods and $\tau \to 3\pi \nu$ decays for Higgs boson parity measurement.

We consider a charged scalar field in a $D$-dimensional de Sitter spacetime and investigate pair creation by a Schwinger mechanism in a constant electric field background. Using a semiclassical approximation the current of the created pairs has been estimated. We find that the semiclassical current of the created pairs in the strong electric field limit responds as $E^{\frac{D}{2}}$. Going further but restricting to $D=3$ dimensional de Sitter spacetime, the quantum expectation value of the spacelike component of the induced current has been computed in the in-vacuum state by applying an adiabatic subtraction scheme. We find that, in the strong electric field limit, the current responds as $E^{\frac{3}{2}}$. In the weak electric field limit the current has a linear response in $E$ and an inverse dependence on the mass of the scalar field. In the case of a massless scalar field, the current varies with $E^{-1}$ which leads to a phenomenon of infrared hyperconductivity. A new relation between infrared hyperconductivity, tachyons, and conformality is discussed, and a scheme to avoid an infrared hyperconductivity regime is proposed. In $D$ dimension, we eventually presented some first estimates of the backreaction of the Schwinger pairs to the gravitational field, and we find a decrease of the Hubble constant due to the pair creation.

We consider a spinning test-body in circular motion around a nonrotating black hole and analyze different prescriptions for the body’s dynamics. We compare, for the first time, the Mathisson-Papapetrou formalism under the Tulczyjew spin-supplementary condition (SSC), the Pirani SSC, and the Ohashi-Kyrian-Semerak SSC, and the spinning particle limit of the effective-one-body Hamiltonian of Damour and Nagar [Phys. Rev. D 90, 044018 (2014).]. We analyze the four different dynamics in terms of the innermost stable circular orbit (ISCO) shifts and in terms of the coordinate-invariant binding energies, separating higher-order spin contributions from spin-orbit contributions. The asymptotic gravitational-wave fluxes produced by the spinning body are computed by solving the inhomogeneous $(2+1)D$ Teukolsky equation and contrasted for the different cases. For small orbital frequencies $\mathrm{\Omega }$, all the prescriptions reduce to the same dynamics and the same radiation fluxes. For large frequencies, $x\equiv (M\mathrm{\Omega }{)}^{2/3}>0.1$, where $M$ is the black hole mass, and especially for positive spins (aligned with the orbital angular momentum) a significant disagreement between the different dynamics is observed. The ISCO shifts can differ by up to a factor of 2 for large positive spins; for the Ohashi-Kyrian-Semerak and the Pirani SSC the ISCO diverges around dimensionless spins $\sim 0.52$ and $\sim 0.94$, respectively. In the spin-orbit part of the energetics the deviation from the Hamiltonian dynamics is largest for the Ohashi-Kyrian-Semerak SSC; it exceeds 10% for $x>0.17$. The Tulczyjew and the Pirani SSCs are compatible across almost the whole spin and frequency range. Our results will have direct applications in including spin effects in effective-one-body waveform models for circularized binaries in the extreme-mass-ratio limit.

We numerically determine the cosmological branch of the free function in a nonlocal metric-based modification of gravity which provides a relativistic generalization of Milgrom’s modified Newtonian dynamics. We are able to reproduce the $\mathrm{\Lambda }\mathrm{CDM}$ expansion history over virtually all of cosmic history, including the era of radiation domination during big bang nucleosynthesis, the era of matter domination during recombination, and most of the era of vacuum energy domination. The very late period of $0\le z\lesssim 0.0880$, during which the model deviates from the $\mathrm{\Lambda }\mathrm{CDM}$ expansion history, is interesting because it causes the current value of the Hubble parameter to be about 4.5% larger than it would be for the $\mathrm{\Lambda }\mathrm{CDM}$ model. This may resolve the tension between inferences of $H_0$ which are based on data from large redshift and inferences based on Hubble plots.

We study the $D_s^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}$ and $D_s^{+}\to {\pi }^{+}{K}^{+}{K}^{-}$ decays adopting a mechanism in which the $D_s^{+}$ meson decays weakly into a ${\pi }^{+}$ and a $q\overline{q}$ component, which hadronizes into two pseudoscalar mesons. The final state interaction between these two pseudoscalar mesons is taken into account by using the chiral unitary approach in coupled channels, which gives rise to the $f_0(980)$ resonance. Hence, we obtain the invariant mass distributions of the pairs ${\pi }^{+}{\pi }^{-}$ and $K^{+}{K}^{-}$ after the decay of that resonance and compare our theoretical amplitudes with those available from the experimental data. Our results are in a fair agreement with the shape of these data, within large experimental uncertainty, and a $f_0(980)$ signal is seen in both the ${\pi }^{+}{\pi }^{-}$ and $K^{+}{K}^{-}$ distributions. Predictions for the relative size of ${\pi }^{+}{\pi }^{-}$ and $K^{+}{K}^{-}$ distributions are made.

Effective Lagrangians are a useful tool for a data-driven approach to physics beyond the Standard Model at the LHC. However, for the new physics scales accessible at the LHC, the effective operator expansion is only relatively slowly converging at best. For tree-level processes, it has been found that the agreement between the effective Lagrangian and a range of UV-complete models depends sensitively on the appropriate definition of the matching. We extend this analysis to the one-loop level, which is relevant for electroweak precision data and Higgs decay to photons. We show that near the scale of electroweak symmetry breaking the validity of the effective theory description can be systematically improved through an appropriate matching procedure. In particular, we find a significant increase in accuracy when including suitable terms suppressed by the Higgs vacuum expectation value in the matching.

The $CP$-even static form factors $\mathrm{\Delta }{\kappa }_V^{\prime }$ and $\mathrm{\Delta }{Q}_V$ ($V=\gamma$, $Z$) associated with the $WWV$ vertex are studied in the context of the Georgi-Machacek model (GMM), which predicts nine new scalar bosons accommodated in a singlet, a triplet, and a fiveplet. General expressions for the one-loop contributions to $\mathrm{\Delta }{\kappa }_V^{\prime }$ and $\mathrm{\Delta }{Q}_V$ arising from neutral, singly, and doubly charged scalar bosons are obtained in terms of both parametric integrals and Passarino-Veltman scalar functions, which can be numerically evaluated. It is found that the GMM yields 15 (28) distinct contributions to $\mathrm{\Delta }{\kappa }_{\gamma }^{\prime }$ and $\mathrm{\Delta }{Q}_{\gamma }$ ($\mathrm{\Delta }{\kappa }_Z^{\prime }$ and $\mathrm{\Delta }{Q}_Z$), though several of them are naturally suppressed. A numerical analysis is done in the region of parameter space still consistent with current experimental data and it is found that the largest contributions to $\mathrm{\Delta }{\kappa }_V^{\prime }$ arise from Feynman diagrams with two nondegenerate scalar bosons in the loop, with values of the order of $a=g^2/(96{\pi }^2)$ reached when there is a large splitting between the masses of these scalar bosons. As for $\mathrm{\Delta }{Q}_V$, it reaches values as large as ${10}^{-2}a$ for the lightest allowed scalar bosons, but it decreases rapidly as one of the masses of the scalar bosons becomes large. Among the new contributions of the GMM to the $\mathrm{\Delta }{\kappa }_V^{\prime }$ and $\mathrm{\Delta }{Q}_V$ form factors are those induced by the $H_5^{\pm }{W}^{\mp }Z$ vertex, which arises at the tree level and is a unique prediction of this model.

Following a recent work on the effective description of the equations of state for hot QCD obtained from a hard thermal loop expression for the gluon self-energy, in terms of the quasigluons and quasiquarks and antiquarks with respective effective fugacities, the dissociation process of heavy quarkonium in hot QCD medium has been investigated. This has been done by investigating the medium modification to a heavy quark potential. The medium-modified potential has a quite different form (a long-range Coulomb tail in addition to the usual Yukawa term) in contrast to the usual picture of Debye screening. The flavor dependence binding energies of the heavy quarkonia states and the dissociation temperature have been obtained by employing the Debye mass for pure gluonic and full QCD case computed employing the quasiparticle picture. Thus, estimated dissociation patterns of the charmonium and bottomonium states, considering Debye mass from different approaches in the pure gluonic case and full QCD, have shown good agreement with the other potential model studies.

The recently proposed quasidistributions point out a promising direction for lattice QCD to investigate the light-cone correlators, such as parton distribution functions and distribution amplitudes (DAs), directly in the $x$ space. Owing to its excessive simplicity, heavy quarkonium can serve as an ideal theoretical laboratory to ascertain certain features of quasi-DAs. In the framework of nonrelativistic QCD factorization, we compute the order-${\alpha }_s$ correction to both light-cone distribution amplitudes (LCDAs) and quasi-DAs associated with the lowest-lying quarkonia, with the transverse-momentum UV cutoff interpreted as the renormalization scale. We confirm analytically that the quasi-DA of a quarkonium does reduce to the respective LCDA in the infinite-momentum limit. We also observe that, provided that the momentum of a charmonium reaches about 2–3 times its mass, the quasi-DAs already converge to the LCDAs to a decent level. These results might provide some useful guidance for the future lattice study of quasidistributions.

Progress in the calculation of the electromagnetic properties of baryon excitations in lattice QCD presents new challenges in the determination of sea-quark loop contributions to matrix elements. A reliable estimation of the sea-quark loop contributions represents a pressing issue in the accurate comparison of lattice QCD results with experiment. In this article, an extension of the graded symmetry approach to partially quenched QCD is presented, which builds on previous theory by explicitly including flavor-singlet baryons in its construction. The formalism takes into account the interactions among both octet and singlet baryons, octet mesons, and their ghost counterparts; the latter enables the isolation of the quark-flow disconnected sea-quark loop contributions. The introduction of flavor-singlet states enables systematic studies of the internal structure of $\mathrm{\Lambda }$-baryon excitations in lattice QCD, including the topical $\mathrm{\Lambda }(1405)$.

This paper considers the spontaneous violation of Lorentz symmetry by the vacuum condensation of an antisymmetric two-tensor. The coset construction for nonlinear realization of spacetime symmetries is employed to build the most general low-energy effective action for the Goldstone modes interacting with photons. We analyze the model within the context of the Standard-Model extension and noncommutative QED. Experimental bounds for some parameters of the model are discussed, and we readdress the subtle issues of stability and causality in Lorentz-noninvariant scenarios. To set a sensible low-energy effective model, in addition to the two photon polarizations only one Goldstone mode must be dynamical, and the enhancement of the stability by accounting for interaction terms points to a protection against observational Lorentz violation.

We discuss the nonperturbative contributions from real and complex saddle point solutions in the $\mathbb{C}{P}^1$ quantum mechanics with fermionic degrees of freedom, using the Lefschetz thimble formalism beyond the Gaussian approximation. We find bion solutions, which correspond to (complexified) instanton-anti-instanton configurations stabilized in the presence of the fermionic degrees of freedom. By computing the one-loop determinants in the bion backgrounds, we obtain the leading order contributions from both the real and complex bion solutions. To incorporate quasizero modes which become nearly massless in a weak coupling limit, we regard the bion solutions as well-separated instanton-anti-instanton configurations and calculate a complexified quasimoduli integral based on the Lefschetz thimble formalism. The nonperturbative contributions from the real and complex bions are shown to cancel out in the supersymmetric case and give an (expected) ambiguity in the nonsupersymmetric case, which plays a vital role in the resurgent trans-series. For nearly supersymmetric situations, evaluation of the Lefschetz thimble gives results in precise agreement with those of the direct evaluation of the Schrödinger equation. We also perform the same analysis for the sine-Gordon quantum mechanics and point out some important differences showing that the sine-Gordon quantum mechanics does not correctly describe the 1d limit of the $\mathbb{C}{P}^{N-1}$ field theory of $\mathbb{R}\times S^1$.

The expressions for the quasinormal modes (QNM) of black holes with nonlinear electrodynamics, calculated in the eikonal approximation, are presented. In the eikonal limit QNM of black holes are determined by the parameters of the circular null geodesics. The unstable circular null orbits are derived from the effective metric that is the one obeyed by light rays under the influence of a nonlinear electromagnetic field. As an illustration we calculate the QNM of four nonlinear electromagnetic black holes, two singular and two regular, namely, from Euler-Heisenberg and Born-Infeld theories, for singular ones, and the magnetic Bardeen black hole and the one derived by Bronnikov for regular ones. Comparing with the QNM of the linear electromagnetic counterpart, their Reissner-Nordström black hole is done.

We study the evolution of black hole entropy and temperature in collapse scenarios in asymptotically anti–de Sitter spacetime, finding three generic lessons. First, entropy evolution is extensive. Second, at large times, entropy and temperature ring with twice the frequency of the lowest quasinormal mode. Third, the entropy oscillations saturate black hole area theorems in general relativity. The first two features are characteristic of entanglement dynamics in “democratic” models. Solely based on general relativity and the Bekenstein-Hawking entropy formula, our results point to democratic models as microscopic theories of black holes. The third feature can be taken as a prediction for microscopic models of black hole physics.