Photon operators with the proper $J^{PC}$ quantum numbers are constructed, including one made of elementary plaquettes. In compact U(1) lattice gauge theory, these explicit photon operators are shown to permit direct confirmation of the massive and massless states on each side of the phase transition. In the Abelian Higgs model, these explicit photon operators avoid some excited state contamination seen with the traditional composite operator, and allow more detailed future studies of the Higgs mechanism.

A set of four finite energy QCD sum rules are used to determine the magnetic field dependence of the sum of the up- and down-quark masses of QCD, ($m_u+m_d$), the pion decay constant $f_{\pi }$, the pion mass $m_{\pi }$, the gluon condensate, $⟨{\alpha }_s{G}^2⟩$, and the squared energy threshold for the onset of perturbative QCD, $s_0$, related to the Polyakov loop of lattice QCD. As a first input we take the magnetic evolution of the chiral quark condensate from lattice QCD and/or Nambu–Jona-Lasinio results. As a second input we take three different possible conditions concerning the quark and pion masses.

The decay ${\tau }^{-}\to K^{-}{K}_S{\nu }_{\tau }$ has been studied using $430\times {10}^6$ $e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}$ events produced at a center-of-mass energy around 10.6 GeV at the PEP-II collider and studied with the BABAR detector. The mass spectrum of the $K^{-}{K}_S$ system has been measured and the spectral function has been obtained. The measured branching fraction $\mathcal{B}({\tau }^{-}\to K^{-}{K}_S{\nu }_{\tau })=(0.739\pm 0.011(\mathrm{stat})\pm 0.020(\mathrm{syst}))\times {10}^{-3}$ is found to be in agreement with earlier measurements.

A search for direct pair production of top squarks in final states with two tau leptons, $b$-jets, and missing transverse momentum is presented. The analysis is based on proton-proton collision data at $\sqrt{s}=13\mathrm{TeV}$ corresponding to an integrated luminosity of $36.1{\mathrm{fb}}^{-1}$ recorded with the ATLAS detector at the Large Hadron Collider in 2015 and 2016. Two exclusive channels with either two hadronically decaying tau leptons or one hadronically and one leptonically decaying tau lepton are considered. No significant deviation from the Standard Model predictions is observed in the data. The analysis results are interpreted in terms of model-independent limits and used to derive exclusion limits on the masses of the top squark ${\tilde{t}}_1$ and the tau slepton ${\tilde{\tau }}_1$ in a simplified model of supersymmetry with a nearly massless gravitino. In this model, masses up to $m({\tilde{t}}_1)=1.16\mathrm{TeV}$ and $m({\tilde{\tau }}_1)=1.00\mathrm{TeV}$ are excluded at 95% confidence level.

We construct a formalism for evolving spherically symmetric black hole initial data sets within a canonical approach to quantum gravity. This problem can be formulated precisely in quantum reduced loop gravity, a framework which has been successfully applied to give a full theory derivation of loop quantum cosmology. We extend this setting by implementing a particular choice of partial gauge which is then used to select a kinematical Hilbert space where the symmetry reduction is imposed through semiclassical states. The main result of this investigation is an effective Hamiltonian that can be used to solve for quantum black hole geometries by evolving classical black hole initial data sets.

The requirement of the existence of a holographic c-function for higher derivative theories is a very restrictive one, and hence most theories do not possess this property. Here, we show that, when some of the parameters are fixed, the $D\ge 3$ Born-Infeld gravity theories admit a holographic c-function. We work out the details of the $D=3$ theory with no free parameters, which is a nonminimal Born-Infeld type extension of new massive gravity. Moreover, we show that these theories generate an infinite number of higher derivative models admitting a c-function in a suitable expansion, and therefore they can be studied at any truncated order.

We consider a scalar field model with a $g{\varphi }_4^4$ interaction and compute the mass correction at next-to-leading order in a large-$N$ expansion to study the summability of the perturbative series. It is already known that at zero temperature this model has a singularity in the Borel plane (a “renormalon”). We find that a small increase in temperature adds two countable sets both with an infinite number of renormalons. For one of the sets the position of the poles is thermal independent and the residue is thermal dependent. In the other one both the position of poles and the residues are thermal dependent. However, if we consider the model at extremely high temperatures, such that a dimensional reduction takes place, one observes that all the renormalons disappear and the model becomes Borel summable.

Two-dimensional QCD with adjoint fermions has many attractive features, yet its single-particle content remains largely unknown. To lay the foundation for a crucially improved approximation of the theory’s spectrum, we developed a method to find the basis of eigenstates using the symmetry structure of the asymptotic theory where pair production is disallowed. This method produces complete sets of multidimensional harmonic functions for the massless and the massive theory. Previously only part of such a basis was known. The method presented here should be applicable to other theories and has the promise of factoring out the long-range Coulomb-type part of interactions. The role of pair production and implications for the bosonized theory in the case of adjoint ${\mathrm{QCD}}_2$ are discussed.

We cut and paste two Bañados-Teitelboim-Zanelli (BTZ) spacetimes at a throat by the Darmois-Israel method to construct a rotating wormhole with a thin shell filled with a barotropic fluid. The thin shell at the throat and both sides of the throat corotate. We investigate the linear stability of the thin shell of the rotating wormhole against radial perturbations. We show that the wormhole becomes more and more stable the larger its angular momentum is until the angular momentum reaches a critical value and that the behavior of a condition for stability significantly changes when the angular momentum exceeds the critical value. We find that the overcritical rotating wormhole has the radius of the thin shell, which is stable regardless of the equation of state for the barotropic fluid.

Assuming a nongravitational interaction among the dark fluids of our Universe—namely, dark matter and dark energy—we study a specific interaction model in the background of a spatially flat Friedmann-Lemaître-Robertson-Walker geometry. We find that the interaction model solves the background evolution in an analytic way when the dark energy takes a constant barotropic equation of state, $w_x$. In particular, we analyze two separate interaction scenarios, namely, when the dark energy is a fluid other than the vacuum energy (i.e., $w_x\ne -1$) and when it is vacuum energy itself (i.e., $w_x=-1$). We find that the interacting model with $w_x\ne -1$ produces stable perturbations at large scales for $w_x<-1$ with the coupling strength $\xi <0$. Both scenarios are constrained by the latest astronomical data. The analyses show that a very small interaction with the coupling strength is allowed, and within the 68.3% confidence region $\xi =0$ is recovered. The analyses further show that a large coupling strength significantly affects the large-scale dynamics of the Universe, while according to the observational data the interaction models are very well consistent with $\mathrm{\Lambda }$ cosmology. Furthermore, we observe that for the vacuum interaction scenario, the tension on $H_0$ is not released while for the interacting dark energy scenario with $w_x<-1$, the tension on $H_0$ seems to be released partially because of the high error bars in $H_0$. Finally, we conclude the work by calculating the Bayesian evidence, which shows that $\mathrm{\Lambda }\mathrm{CDM}$ cosmology is favored over the two interacting scenarios.

We study anisotropic inflation in the Brans-Dicke gravity in the presence of a non-Abelian gauge field where the gauge field is nonminimally coupled to the inflaton. We consider the displaced quadratic potential for the inflation. We find out that the solution of equations of motion is an attractor in the phase space. Moreover, anisotropy grows with the number of $e$-folds. It may become either positive or negative in contradiction to the Abelian gauge field coupling. The anisotropy depends on the Brans-Dicke parameter and constant parameter of the coupling function of the scalar field and the non-Abelian gauge field.

We advocate the idea that there is a fundamentally new mechanism for the axion production in the Sun, which has never been discussed previously in the literature. This novel mechanism of the axion production is based on the so-called sxion quark nugget (AQN) dark matter model. These axions will be produced in addition to well-studied axions emitted due to the Primakoff effect. The AQN model was originally invented as a natural explanation of the observed ratio ${\mathrm{\Omega }}_{\mathrm{dark}}\sim {\mathrm{\Omega }}_{\text{visible}}$ when the DM and visible matter densities assume the same order of magnitude values, irrespective to the axion mass $m_a$ or initial misalignment angle ${\theta }_0$. This model, without adjustment of any parameters, reproduces reasonably the intensity of the extreme UV (EUV) radiation from the solar corona as a result of the AQN annihilation events with the solar material. This extra energy released in the corona represents a resolution, within the AQN framework, a long-standing puzzle known in the literature as the “solar corona heating mystery.” The same annihilation events also produce the relativistic axions. This represents a new mechanism of the axion production and constitutes the main subject of this work. The flux of these axions is unambiguously fixed in this model and expressed in terms of the EUV luminosity from the corona. We also compute the spectral properties of these axions and make a few comments on the potential for the discovery of these solar axions by the upgraded CAST (CERN Axion Solar Axion) experiment.

X-ray observations of some short gamma-ray bursts indicate that a long-lived neutron star can form as a remnant of a binary neutron star merger. We develop a gravitational-wave detection pipeline for a long-lived binary neutron star merger remnant guided by these counterpart electromagnetic observations. We determine the distance out to which a gravitational-wave signal can be detected with Advanced LIGO at design sensitivity and the Einstein Telescope using this method, guided by x-ray data from GRB140903A as an example. Such gravitational waves can, in principle, be detected out to $\sim 20\mathrm{Mpc}$ for Advanced LIGO and $\sim 450\mathrm{Mpc}$ for the Einstein Telescope assuming a fiducial ellipticity of ${10}^{-2}$. However, in practice, we can rule out such high values of the ellipticity as the total energy emitted in gravitational waves would be greater than the total rotational energy budget of the system. We show how these observations can be used to place upper limits on the ellipticity using these energy considerations. For GRB140903A, the upper limit on the ellipticity is ${10}^{-3}$, which lowers the detectable distance to $\sim 2\mathrm{Mpc}$ and $\sim 45\mathrm{Mpc}$ for Advanced LIGO and the Einstein Telescope, respectively.

Recently, there has been significant interest in understanding the macroscopic quantum transport in a many-body system of chiral fermions. A natural framework for describing such a system that is generally out of equilibrium is the transport equation for its phase space distribution function. In this paper, we obtain a complete solution of the covariant chiral transport for massless fermions, by starting from the general Wigner function formalism and carrying out a complete and consistent semiclassical expansion up to $\widehat{\mathbf{O}}(\hslash )$ order. In particular, we clarify certain subtle and confusing issues surrounding the Lorentz noninvariance and frame dependence associated with the three-dimensional chiral kinetic theory. We prove that such frame dependence is uniquely and completely fixed by an unambiguous definition of the $\widehat{\mathbf{O}}(\hslash )$ correction to the distribution function in each reference frame.

We propose using interferometry of circularly polarized light as a mechanism by which to test for axion dark matter. These interferometers differ from standard interferometers only by the addition of a few quarter wave plates to preserve the polarization of light upon reflection. We show that using current technology, interferometers can probe new regions of axion parameter space up to a couple orders of magnitude beyond current constraints.

Surveys of diffuse $\gamma$ rays in the interstellar medium (ISM) can be used to probe hydrogen-antihydrogen oscillations, by detecting the $\gamma$-ray emission from antihydrogen annihilation. A bound on the oscillation parameter $\delta$ was originally derived by Feinberg, Goldhaber, and Steigman (1978). In this paper, we revisit the original derivation by performing a more detailed analysis that (1) incorporates suppression effects from additional elastic and inelastic processes, (2) treats the ISM as a multiphase medium, and (3) utilizes more recent $\gamma$-ray data from the Fermi Large Area Telescope. We find that suppression from elastic scattering plays a more important role than previously thought, while the multiphase nature of the ISM affects how the $\gamma$-ray data should be utilized. We derive a more accurate bound on the oscillation period that is about an order of magnitude weaker than the older bound.

Extensions of the standard model which address the hierarchy problem and dark matter (DM) often contain top partners and additional resonances at the TeV scale. We explore the phenomenology of a simplified effective model with a vector resonance $Z^{\prime }$, a fermionic vectorlike colored partner of the top quark $T^{\prime }$ as well as a scalar DM candidate $\varphi$ and provide publicly available implementations in CalcHEP and MadGraph. We study the $pp\to Z^{\prime }\to T^{\prime }\overline{T^{\prime }}\to t\overline{t}\varphi \varphi$ process at the LHC and find that it plays an important role in addition to the $T^{\prime }\overline{T^{\prime }}$ production via strong interactions. It turns out that the presence of the $Z^{\prime }$ can provide a dominant contribution to the $t\overline{t}+{\cancel{E}}_T$ signature without conflicting with existing bounds from $Z^{\prime }$ searches in di-jet and di-lepton final states. We find that, through this process, the LHC is already probing DM masses up to about 900 GeV and top partner masses up to about 1.5 TeV, thus exceeding the current bounds from QCD production alone almost by a factor of 2 for both particles.

In this paper, we show that the $J/\psi$ production in DIS is the main source of information about the events with two-parton shower production. We attempt to develop our theoretical acumen of this process, to a level compatible with the theoretical description of inclusive DIS. We revisit the problem of the linear evolution equation for the double gluon densities and include Bose-Einstein enhancement to these equations. We find that the Bose-Einstein correlations lead to an increase of the anomalous dimension, which turns out to be suppressed as $1/(N_c^2-1{)}^2$, in agreement with the estimates for the twist-four anomalous dimension. We believe that understanding what happens to these contributions at ultra high energies, is a key question for an effective theory, based on high energy QCD. We derive the evolution equation for the scattering amplitude of two dipoles with a nucleus, taking into account the shadowing corrections, and investigate the analytical solutions in two distinct kinematic regions: deep in the saturation region and in the vicinity of the saturation scale. The suggested nonlinear evolution equation is a direct generalization of the Balitsky-Kovchegov equation, which has to be solved with the initial condition that depends on the saturation scale $Q_s(Y=Y_0,b)$. With the goal of finding a new small parameter, it is instructive to compare the solution of the nonlinear equation with the qusi-classical approximation, in which in the initial condition we replace $Q_s(Y=Y_0,b)$ by $Q_s(Y,b)$. Our final result is that the shadowing corrections in the elastic amplitude generate the survival probability, which suppresses the growth of the amplitude with energy, caused by the Bose-Einstein enhancement.