We evaluate the electromagnetic spectral function and its spectral properties by computing the one-loop photon polarization tensor involving quarks in the loop, particularly in a strong-field approximation compared to the thermal scale. When the magnetic scale is higher than the thermal scale the lowest Landau level (LLL) becomes an effectively ($1+1$)-dimensional strongly correlated system that provides a kinematical threshold based on the quark mass scale. Beyond this threshold the photon strikes the LLL and the spectral strength starts with a high value due to the dimensional reduction and then falls off with the increase of the photon energy due to LLL dynamics in a strong-field approximation. We obtain analytically the dilepton production rates from the LLL considering the lepton pair remains unaffected by the magnetic field when produced at the edge of a hot magnetized medium or it is affected by the magnetic field if produced inside a hot magnetized medium. For the latter case the production rate is of $\mathcal{O}[|eB{|}^2]$ along with an additional kinematical threshold due to the lepton mass. We also investigate the electromagnetic screening by computing the Debye screening mass and it depends distinctively on three different scales (mass of the quasiquark, temperature and the magnetic field strength) of a hot magnetized system. The mass dependence of the Debye screening supports the occurrence of a magnetic catalysis effect in the strong-field approximation.

We demonstrate that a purposefully normalized next-to-next-to-leading-order $m_{t\overline{t}}$ differential spectrum can have very small theoretical uncertainty and, in particular, a small sensitivity to the top quark mass. Such an observable can thus be a very effective bump-hunting tool for resonances decaying to $t\overline{t}$ events during LHC run II and beyond. To illustrate how the approach works, we concentrate on one specific example of current interest, namely, the possible 750 GeV digamma excess resonance $\mathrm{\Phi }$. Considering only theoretical uncertainties, we demonstrate that it is possible to distinguish $pp\to \mathrm{\Phi }\to t\overline{t}$ signals studied in the recent literature [Hespel, Maltoni, and Vryonidou, J. High Energy Phys. 10 (2016) 016] from the pure Standard Model background with very high significance. Alternatively, in the case of nonobservation, a strong upper limit on the decay rate $\mathrm{\Phi }\to t\overline{t}$ can be placed.

We compute the electrical conductivity of quark-gluon plasma in a strong magnetic field $B$ with quantum field theory at finite temperature using the lowest Landau level approximation. We provide the one-loop result arising from 1-to-2 scattering processes of which the kinematics are satisfied by the ($1+1$)-dimensional fermion dispersion relation. Because of the chirality conservation, the conductivity diverges in the massless limit and is sensitive to the value of the current quark mass. As a result, we find that the conductivity along the direction of the magnetic field is quite large compared with the value at $B=0$, mainly because of the small value of the current quark mass. We show that the resummation of the ladder diagrams for the current-current correlator gives rise to only subleading contributions beyond the leading-log order and thus verify our one-loop result at the leading-log accuracy. We also discuss possible implications for the relativistic heavy-ion collisions.

We have studied the differential cross section as well as the longitudinal and perpendicular components of polarization of the final hyperon ($\mathrm{\Lambda }$,$\mathrm{\Sigma }$) produced in the antineutrino induced quasielastic charged current reactions on nucleon and nuclear targets. The nucleon-hyperon transition form factors are determined from the experimental data on quasielastic $(\mathrm{\Delta }S=0)$ charged current (anti)neutrino-nucleon scattering and the semileptonic decay of neutron and hyperons assuming G-invariance, T-invariance, and SU(3) symmetry. The vector transition form factors are obtained in terms of nucleon electromagnetic form factors for which various parametrizations available in the literature have been used. A dipole parametrization for the axial vector form factor and the pseudoscalar transition form factor derived in terms of the axial vector form factor assuming PCAC and GT relation extended to the strangeness sector has been used in numerical evaluations. The flux averaged cross section and polarization observables corresponding to the CERN Gargamelle experiment have been calculated for quasielastic hyperon production and found to be in reasonable agreement with the experimental observations. The numerical results for the flux averaged differential cross section $\frac{d\sigma }{d{Q}^2}$ and longitudinal (perpendicular) polarization $P_L(Q^2)(P_P(Q^2))$ relevant for the antineutrino fluxes of $\mathrm{MINER}\nu \mathrm{A}$, MicroBooNE, and T2K experiments have been presented. This will be useful in interpreting future experimental results on production cross sections and polarization observables from the experiments on the quasielastic production of hyperons induced by antineutrinos and exploring the possibility of determining the axial vector and pseudoscalar form factors in the strangeness sector.

We present results for the isotriplet and isosinglet tensor form factors of the nucleon in the relativistic confined quark model. The model allows us to calculate not only their normalizations at $Q^2=0$ and the related tensor charges, but also the full $Q^2$-dependence. Our results are compared to existing data and predictions of other theoretical approaches. We stress the importance of these form factors for the phenomenology of physics beyond the Standard Model.

We propose an improved version of the color evaporation model to describe heavy quarkonium production. In contrast to the traditional color evaporation model, we impose the constraint that the invariant mass of the intermediate heavy quark-antiquark pair be larger than the mass of produced quarkonium. We also introduce a momentum shift between the heavy quark-antiquark pair and the quarkonium. Numerical calculations show that our model can describe the charmonium yields as well as the ratio of ${\psi }^{\prime }$ over $J/\psi$ better than the traditional color evaporation model.

We study Earth matter effect in oscillations of supernovae neutrinos. We show that detecting Earth matter effect gives an independent measurement of spectra of supernovae neutrinos, i.e., the flavor difference of the spectra of supernovae neutrinos. We study the effect of energy resolution and angular resolution of a final electron or positron on detecting the signal of Earth matter effect. We show that varying the widths of energy bins in analysis can change the signal strength of Earth matter effect and the statistical fluctuation. A reasonable choice of energy bins can both suppress the statistical fluctuation and make a good signal strength relative to the statistical fluctuation. Neutrino detectors with good energy resolution and good angular resolution are therefore preferred so that there is more freedom to vary energy bins and to optimize the signal of Earth matter effect in analyzing events of supernovae neutrinos.

In the coset model based on $(A_{N-1}^{(1)}\oplus A_{N-1}^{(1)},A_{N-1}^{(1)})$ at level $(N,N;2N)$, it is known that the $\mathcal{N}=2$ superconformal algebra can be realized by the two kinds of adjoint fermions. Each Kac-Moody current of spin 1 is given by the product of fermions with structure constant ($f$ symbols) as usual. One can construct the spin-1 current by combining the above two fermions with the structure constant and the spin-1 current by multiplying these two fermions with a completely symmetric $SU(N)$ invariant tensor of rank 3 ($d$ symbols). The lowest higher spin-2 current with nonzero $U(1)$ charge (corresponding to the zero mode eigenvalue of the spin-1 current of $\mathcal{N}=2$ superconformal algebra) can be obtained from these four spin-1 currents in quadratic form. Similarly, the other type of lowest higher spin-2 current, whose $U(1)$ charge is opposite to the above one, can be obtained also. Four higher spin-$\frac{5}{2}$ currents can be constructed from the operator product expansions (OPEs) between the spin-$\frac{3}{2}$ currents of $\mathcal{N}=2$ superconformal algebra and the above two higher spin-2 currents. The two higher spin-3 currents can be determined by the OPEs between the above spin-$\frac{3}{2}$ currents and the higher spin-$\frac{5}{2}$ currents. Finally, the ten $\mathcal{N}=2$ OPEs between the four $\mathcal{N}=2$ higher spin multiplets $(2,\frac{5}{2},\frac{5}{2},3)$, $(2,\frac{5}{2},\frac{5}{2},3)$, $(\frac{7}{2},4,4,\frac{9}{2})$, and $(\frac{7}{2},4,4,\frac{9}{2})$ are obtained explicitly for generic $N$.

We propose a simplified protocol of quantum energy teleportation (QET) for the holographic conformal field theory in three-dimensional anti–de Sitter space with or without a black hole. As a tentative proposal, we simplify the standard QET by replacing Alice’s local measurement with the local projection, which excites the system from the ground state into a particular state dual to a Banados geometry. We then mimic Bob’s local operation of the usual QET for extracting energy by deforming the UV surface with a local bump. Adopting the surface-state duality, this deformation corresponds to local unitary. We evaluate the extraction of energy from the holographic stress tensor and find that Bob always gains energy extraction in our protocol. This could be related to the positive energy theorem of the dual gravity. Moreover, the ratio of extraction energy to the injection one is a universal function of the UV surface deformation profile.

We study a Maxwell-Proca action in an asymptotically AdS black hole background. When moving the temperature of the black hole, we find rich phase diagrams that depend strongly on the dimension of the operator dual to the Proca field. We present different solutions in the bulk that correspond to the holographic dual for $s$-, $p$-, or $s+p$-wave superfluids. In the last case we observe the onset of a spontaneously induced current.

In this work we study the issue of gauge anomalies in Lorentz-violating QED. To do so, we opt to use the Becchi-Rouet-Stora-Tyutin formalism within the algebraic renormalization approach, reducing our study to a cohomology problem. Since this approach is independent of the renormalization scheme, the results obtained here are expected to be general. We find that the Lorentz-violating QED is free of gauge anomalies to all orders in perturbation theory.

The recently reported gravitational wave events GW150914 and GW151226 caused by the mergers of binary black holes [Abbott et al., Phys. Rev. Lett. 116, 221101 (2016); Phys. Rev. Lett. 116, 241103 (2016); Phys. Rev. X 6, 041015] provide a formidable way to set constraints on alternative metric theories of gravity in the strong field regime. In this paper, we develop an approach where an arbitrary theory of gravity can be parametrized by an effective coupling $G_{\mathrm{eff}}$ and an effective gravitational potential $\mathrm{\Phi }(r)$. The standard Newtonian limit of general relativity is recovered as soon as $G_{\mathrm{eff}}\to G_N$ and $\mathrm{\Phi }(r)\to {\mathrm{\Phi }}_N$. The upper bound on the graviton mass and the gravitational interaction length, reported by the LIGO-VIRGO Collaboration, can be directly recast in terms of the parameters of the theory that allows an analysis where the gravitational wave frequency modulation sets constraints on the range of possible alternative models of gravity. Numerical results based on published parameters for the binary black hole mergers are also reported. The comparison of the observed phases of GW150914 and GW151226 with the modulated phase in alternative theories of gravity does not give reasonable constraints due to the large uncertainties in the estimated parameters for the coalescing black holes. In addition to these general considerations, we obtain limits for the frequency dependence of the $\alpha$ parameter in scalar tensor theories of gravity.

We study the Einstein-SO(3)Yang-Mills-Higgs system with a negative cosmological constant and find the monopole black hole solutions as well as the trivial Reissner-Nordström black hole. We discuss thermodynamical stability of the monopole black hole in an isolated system. We expect a phase transition between those two black holes when the mass of a black hole increases or decreases. The type of phase transition depends on the cosmological constant $\mathrm{\Lambda }$, as well as the vacuum expectation value $v$ and the coupling constant $\lambda$ of the Higgs field. Keeping $\lambda$ small, we find there are two critical values of the cosmological constant, ${\mathrm{\Lambda }}_{\text{cr}(1)}(v)$ and ${\mathrm{\Lambda }}_{\mathrm{cr}(2)}(v)$, which depend on $v$. If ${\mathrm{\Lambda }}_{\mathrm{cr}(1)}(v)<\mathrm{\Lambda }(<0)$, we find the first order transition, whereas if ${\mathrm{\Lambda }}_{\mathrm{cr}(2)}(v)<\mathrm{\Lambda }<{\mathrm{\Lambda }}_{\mathrm{cr}(1)}(v)$, the transition becomes second order. For the case of ${\mathrm{\Lambda }}_b(v)<\mathrm{\Lambda }<{\mathrm{\Lambda }}_{(2)}(v)$, we again find the first order irreversible transition from the monopole black hole to the extreme Reissner-Nordström black hole. Beyond ${\mathrm{\Lambda }}_b(v)$, no monopole black hole exists. We also discuss thermodynamical properties of the monopole black hole in a thermal bath system.

Wave function collapse models postulate a fundamental breakdown of the quantum superposition principle at the macroscale. Therefore, experimental tests of collapse models are also fundamental tests of quantum mechanics. Here, we compute the upper bounds on the collapse parameters, which can be inferred by the gravitational wave detectors LIGO, LISA Pathfinder, and AURIGA. We consider the most widely used collapse model, the continuous spontaneous localization (CSL) model. We show that these experiments exclude a huge portion of the CSL parameter space, the strongest bound being set by the recently launched space mission LISA Pathfinder. We also rule out a proposal for quantum-gravity-induced decoherence.

We illustrate how it is possible to calculate the quantum gravitational effects on the spectra of primordial scalar/tensor perturbations starting from the canonical, Wheeler-De Witt, approach to quantum cosmology. The composite matter-gravity system is analyzed through a Born-Oppenheimer approach in which gravitation is associated with the heavy degrees of freedom and matter (here represented by a scalar field) with the light ones. Once the independent degrees of freedom are identified, the system is canonically quantized and a semiclassical approximation is used for the scale factor. The differential equation governing the dynamics of the primordial spectra with their quantum-gravitational corrections is then obtained and is applied to diverse inflationary evolutions. Finally, the analytical results are compared to observations through a Monte Carlo Markov chain technique and an estimate of the free parameters of our approach is finally presented and the results obtained are compared with previous ones.

Loop amplitudes are conveniently expressed in terms of master integrals whose coefficients carry the process dependent information. Similarly before integration, the loop integrands may be expressed as a linear combination of propagator products with universal numerator tensors. Such a decomposition is an important input for the numerical unitarity approach, which constructs integrand coefficients from on-shell tree amplitudes. We present a new method to organize multiloop integrands into a direct sum of terms that integrate to zero (surface terms) and remaining master integrands. This decomposition facilitates a general, numerical unitarity approach for multiloop amplitudes circumventing analytic integral reduction. Vanishing integrals are well known as integration-by-parts identities. Our construction can be viewed as an explicit construction of a complete set of integration-by-parts identities excluding doubled propagators. Interestingly, a class of “horizontal” identities is singled out which hold as well for altered propagator powers.

We propose a one-loop radiative Majorana-type neutrino-mass matrix without any kind of additional symmetries by introducing two leptoquark-like bosons only. In this scenario, we show that the anomaly appearing in the process $b\to s\ell \overline{\ell }$ can be explained without any conflicts against various constraints such as lepton-flavor violations, flavor-changing neutral currents, oblique parameters $\mathrm{\Delta }S$, $\mathrm{\Delta }T$, and the Drell-Yan process. We make the predictions for the flavor-violating lepton-pair production ($e\mu$, $e\tau$, and $\mu \tau$) at the LHC, as well as the cross sections for pair production of these leptoquark-like bosons.

We discuss the internal structure of radially excited charmonium mesons based on the equal-time and Coulomb gauge Bethe-Salpeter (BS) amplitudes, which are obtained in lattice QCD. Our simulations are performed with a relativistic heavy-quark action for the charm quark on the ($2+1$)-flavor PACS-CS gauge configurations at the lightest pion mass, $M_{\pi }=156(7)\mathrm{MeV}$. The variational method is applied to the study of the optimal charmonium operators for ground and first excited states of $S$-wave charmonia. We successfully calculate the BS wave functions of ${\eta }_c(2S)$ and $\psi (2S)$ states, as well as ${\eta }_c(1S)$ and $J/\psi$ states, and then estimate the root-mean-square radii of both the $1S$ and $2S$ charmonium states. We also examine whether a series of the BS wave functions from the ground state to excited states can be described by a single set of the spin-independent and spin-dependent interquark potentials with a unique quark mass. It is found that the quark kinetic mass and both the central and the spin-spin charmonium potentials, determined from the $2S$ wave functions, fairly agree with the ones from the $1S$ wave functions. This strongly supports the validity of the potential description for the charmonium system—at least, below the open-charm threshold.

This paper is the first attempt to build a color glass condensate/saturation model based on the next-to-leading-order (NLO) corrections to linear and nonlinear evolution in QCD. We assume that the renormalization scale is the saturation momentum and find that the scattering amplitude has geometric scaling behavior deep in the saturation domain with the explicit formula of this behavior at large $\tau =r^2{Q}_s^2$. We build a model that includes this behavior, as well as the known ingredients: (i) the behavior of the scattering amplitude in the vicinity of the saturation momentum, using the NLO Balitsky-Fadin-Kuraev-Lipatov kernel, (ii) the pre-asymptotic behavior of $\ln (Q_s^2(Y))$, as a function of $Y$, and (iii) the impact parameter behavior of the saturation momentum, which has exponential behavior $\propto \exp (-mb)$ at large $b$. We demonstrate that the model is able to describe the experimental data for the deep inelastic structure function. Despite this, our model has difficulties that are related to the small value of the QCD coupling at $Q_s(Y_0)$ and the large values of the saturation momentum, which indicate the theoretical inconsistency of our description.

The $1/N_c$ expansion method for studying the mass spectrum of excited baryons is shortly reviewed together with applications to mixed symmetric states. The $[\mathbf{70},{\ell }^{+}]$ multiplet, belonging to the $N=2$ band, is reanalyzed, with emphasis on hyperons and the SU(3) symmetry breaking operators entering the mass formula to first order. An important result is that the hierarchy of masses as a function of strangeness is correctly reproduced for all multiplets. Predictions for unknown excited hyperons to $\mathrm{SU}(6)\times \mathrm{O}(3)$ multiplets are made.