Nonstandard neutrino interactions (NSIs), the subleading effects in the flavor transitions of neutrinos, play a crucial role in the determination of the various unknowns in neutrino oscillations, such as neutrino mass hierarchy, the Dirac $CP$ violating phase, and the octant of the atmospheric mixing angle. In this work, we focus on the possible implications of lepton flavor violating (LFV) NSIs, which generally affect the neutrino propagation, on the determination of these unknown oscillation parameters. We study the effect of these NSIs on the physics potential of the currently running and upcoming long-baseline experiments, i.e., T2K, $\mathrm{NO}\nu \mathrm{A}$, and DUNE. We also check the allowed oscillation parameter space in the presence of LFV NSIs.

In the era of precision neutrino physics, we study the influence of nonstandard interactions (NSI) of matter on the question of neutrino mass ordering and its resolution. At long-baseline experiments, since matter effects play a crucial role in addressing this very important question, it is timely to investigate how subleading effects due to NSI may affect and drastically alter inferences pertaining to this question. We demonstrate that the sensitivity to mass ordering gets significantly impacted due to NSI effects for various long-baseline experiments, including the upcoming long-baseline experiment Deep Underground Neutrino Experiment (DUNE). Finally, we draw a comparison between DUNE and the sensitivities offered by two of the current neutrino beam experiments, NOvA and T2K.

Within a dispersive approach to hadronic light-by-light scattering in the muon $g-2$, the evaluation of the numerically dominant pseudoscalar-pole contribution involves the pseudoscalar-photon transition form factor ${\mathcal{F}}_{\mathrm{P}{\gamma }^{*}{\gamma }^{*}}(-Q_1^2,-Q_2^2)$ with $\mathrm{P}={\pi }^0,\eta ,{\eta }^{\prime }$ and, in general, two off-shell photons with spacelike momenta $Q_{1,2}^2$. We show that for ${\pi }^0(\eta ,{\eta }^{\prime })$, the region of photon momenta below about 1(1.5) GeV gives the main contribution to hadronic light-by-light scattering. We then discuss how the precision of current and future measurements of the single- and double-virtual transition form factor in different momentum regions impacts the precision of a data-driven estimate of this contribution to hadronic light-by-light scattering. Based on Monte Carlo simulations for a planned first measurement of the double-virtual form factor at BESIII, we find that for the ${\pi }^0,\eta ,{\eta }^{\prime }$-pole contributions a precision of 14%, 23%, 15% seems feasible. Further improvements can be expected from other experimental data and also from the use of dispersion relations for the different form factors themselves.

The results of a search for the top squark, the supersymmetric partner of the top quark, in final states with one isolated electron or muon, jets, and missing transverse momentum are reported. The search uses the 2015 LHC $pp$ collision data at a center-of-mass energy of $\sqrt{s}=13\mathrm{TeV}$ recorded by the ATLAS detector and corresponding to an integrated luminosity of $3.2{\mathrm{fb}}^{-1}$. The analysis targets two types of signal models: gluino-mediated pair production of top squarks with a nearly mass-degenerate top squark and neutralino and direct pair production of top squarks, decaying to the top quark and the lightest neutralino. The experimental signature in both signal scenarios is similar to that of a top quark pair produced in association with large missing transverse momentum. No significant excess over the Standard Model background prediction is observed, and exclusion limits on gluino and top squark masses are set at 95% confidence level. The results extend the LHC run-1 exclusion limit on the gluino mass up to 1460 GeV in the gluino-mediated scenario in the high gluino and low top squark mass region and add an excluded top squark mass region from 745 to 780 GeV for the direct top squark model with a massless lightest neutralino. The results are also reinterpreted to set exclusion limits in a model of vectorlike top quarks.

We identify the symmetry underlying the recently observed spectral-parameter transformations of holographic Wilson loops alias minimal surfaces in AdS/CFT. The generator of this nonlocal symmetry is shown to furnish a raising operator on the classical Yangian-type charges of symmetric coset models. We explicitly demonstrate how this master symmetry acts on strong-coupling Wilson loops and indicate a possible extension to arbitrary coupling.

We study the loosely bound Skyrme model with the addition of two different pion mass terms; this is the most general potential of polynomial form up to second order in the trace of the Skyrme field. The two pion mass terms are called the standard pion mass term and the modified pion mass term. We find that the binding energies are not reduced by the introduction of the modified pion mass, but it is analogous to the standard pion mass term with a decrease in the value of the mass parameter of the loosely bound potential (for large values of the latter parameter). We find by increasing the overall pion mass that we can reduce the classical binding energy of the 4-Skyrmion to the 2.7% level and the total binding energy including the contribution from spin-isospin quantization is reduced to the 5.8% level.

The density matrix of Hawking radiation is calculated in the model of a black hole with a fluctuating horizon. Quantum fluctuations smear the classical horizon of a black hole and modify the density matrix of radiation producing the off-diagonal elements. The off-diagonal elements may store information on correlations between the radiation and the black hole. The smeared density matrix was constructed by convolution of the density matrix calculated with the instantaneous horizon with the Gaussian distribution over the instantaneous horizons. The distribution has the extremum at the classical radius of the black hole and the width of order of the Planck length. Calculations were performed in the model of a black hole formed by the thin collapsing shell which follows a trajectory that is a solution of the matching equations connecting the interior and exterior geometries.

We present fully dynamical solutions to Einstein-scalar theory in asymptotically anti–de Sitter spacetime with a scalar potential containing particularly rich physics. Depending on one parameter in the potential, we find an especially interesting regime, which exhibits a dynamically unstable black brane, already at zero momentum, while nevertheless having positive specific heat. We show this using the nonlinear dynamics and give a clear interpretation in terms of the spectrum of linearized perturbations. Our results translate directly to their dual strongly coupled nonconformal field theories, whereby we in particular provide two mechanisms to obtain equilibration times much larger than the inverse temperature.

In the scenario of gauge-Higgs unification, the origin of the Higgs boson is the higher-dimensional gauge boson. Very characteristic predictions are made of the Higgs boson interactions in this scenario, reflecting its origin. In particular, a remarkable claim has been made: the contribution of nonzero Kaluza-Klein modes to the Higgs decay $H\to Z\gamma$ exactly vanishes in the minimal SU(3) electroweak unified model, at least at the one-loop level. In this brief paper, in order to see whether this prediction is a general feature of the scenario or the consequence of the specific choice of the model, matter content, or the order of perturbative expansion, we perform an operator analysis. We demonstrate that no relevant operator exists, respecting the gauge symmetry SU(3) in the bulk. We also comment on the possibly important contribution to the photonic decay $H\to \gamma \gamma$ due to the nonzero Kaluza-Klein modes of light quarks.

The LHC potential for discovering doubly charged vector bileptons is investigated considering the measurable process $pp\to {\mu }^{+}{\mu }^{+}{\mu }^{-}{\mu }^{-}X$. The study is performed assuming different bilepton and leptoquark masses. The process cross section is calculated at leading order using the Calchep package. Combining the calculation with the latest ATLAS experiment results at a center-of-mass energy of 7 TeV, bounds on bilepton masses based on LHC data are derived for the first time. The results exclude bilepton masses in the range of 250 GeV to 500 GeV at 95% C.L., depending on the leptoquark mass. Moreover, minimal LHC integrated luminosities needed for discovering and for setting limits on bilepton masses are obtained for 13 TeV center-of-mass energy. Simulated events are passed through a fast parametric detector simulation using the Delphes package.

In this paper, we investigated the process $pp\to W^{-}hj$ induced by the top-Higgs flavor-changing neutral current couplings at the LHC. We found that the cross section of $pp\to W^{-}hj$ mainly comes from the resonant process $pp\to W^{-}t\to W^{-}hq$ due to the anomalous $tqH$ couplings (where $q$ denotes up and charm quarks). We further studied the observability of the top-Higgs flavor-changing neutral current couplings through the process $pp\to W^{-}(\to {\ell }^{-}{\overline{\nu }}_{\ell })h(\to \gamma \gamma )j$ and found that the branching ratios $\mathrm{Br}(t\to qh)$ can be probed to 0.16% at $3\sigma$ level at 14 TeV LHC with an integrated luminosity of $3000{\mathrm{fb}}^{-1}$.

We find a simple analytic solution in open string field theory which, in the on-shell limit, generates a tower of higher-spin vertex operators in bosonic string theory. The solution is related to irregular off-shell vertex operators for Gaiotto states. The wave functions for the irregular vertex operators are described by equations following from the cubic effective action for generalized rolling tachyons, indicating that the evolution from flat to collective higher-spin background in string field theory occurs according to cosmological pattern. We discuss the relation between nonlocalities of the rolling tachyon action and those of higher-spin interactions.

In this work we investigate some features of the fermionic sector of the supersymmetric version of the baby Skyrme model. We find that, in the background of Bogomol’nyi-Prasad-Sommerfield compact baby Skyrmions, fermionic zero modes are confined to the defect core. Further, we show that, while three Supersymmetry (SUSY) generators are broken in the defect core, SUSY is completely restored outside. We study also the effect of a D-term deformation of the model. Such a deformation allows for the existence of fermionic zero modes and broken SUSY outside the compact defect.

The phase structure and the infrared behavior of the Euclidean three-dimensional $O(2)$ symmetric ghost scalar field model with a higher-order derivative term has been investigated in Wegner and Houghton’s renormalization group framework. The symmetric phase in which no ghost condensation occurs and the phase with restored symmetry but with a transient presence of a ghost condensate have been identified. Finiteness of the correlation length at the phase boundary hints to a phase transition of first order. The results are compared with those for the ordinary $O(2)$ symmetric scalar field model.

We study the loop corrections to the scalar propagator and the fermionic self-energy for the mass dimension one fermionic dark matter with the Yukawa interaction. We find, in the former case, there is a nonvanishing Lorentz-violating term while the latter is Lorentz-invariant. Our study of the fermionic loop correction shows that unitarity demands the fermionic mass must be at least half of the bosonic mass and that the Lorentz-violating term makes a nontrivial correction to the bosonic propagator. We discuss what these results mean in the context of the standard model and the possibility of bypassing the unitarity constraint. In the simplest scenario, within the framework of standard quantum field theory, by identifying the scalar boson to be the Higgs boson with a mass of 125 GeV, the mass of the fermion must be at least 62.5 GeV.

We study field theories with $\mathcal{N}$ extended nonlinearly realized supersymmetries, describing the couplings of models that contain $\mathcal{N}$ Goldstini. We review all the known formulations of the $\mathcal{N}=1$ Goldstino theories and we generalize them to an arbitrary number $\mathcal{N}$ of nonlinearly realized supersymmetries. We explicitly prove the equivalence of all these extended supersymmetry breaking models containing $\mathcal{N}$ Goldstini and reformulate the theory with $\mathcal{N}$ supersymmetries in terms of standard $\mathcal{N}=1$ constrained superfields.

We consider a general class of four-dimensional geometries admitting a null vector field that has no twist and no shear but has an arbitrary expansion. We explicitly present the Petrov classification of such Robinson-Trautman (and Kundt) gravitational fields, based on the algebraic properties of the Weyl tensor. In particular, we determine all algebraically special subcases when the optically privileged null vector field is a multiple principal null direction (PND), as well as all the cases when it remains a single PND. No field equations are a priori applied, so that our classification scheme can be used in any metric theory of gravity in four dimensions. In the classic Einstein theory, this reproduces previous results for vacuum spacetimes, possibly with a cosmological constant, pure radiation, and electromagnetic field, but can be applied to an arbitrary matter content. As nontrivial explicit examples, we investigate specific algebraic properties of the Robinson-Trautman spacetimes with a free scalar field, and also black hole spacetimes in the pure Einstein-Weyl gravity.

We study linear nonradial perturbations and stability of a marginal stable circular orbit such as the innermost stable circular orbit of a test particle in stationary axisymmetric spacetimes which possess a reflection symmetry with respect to the equatorial plane. A zenithal stability criterion is obtained in terms of the metric components, the specific energy, and angular momentum of a test particle. The proposed approach is applied to the Kerr solution and Majumdar-Papapetrou solution to the Einstein equation. Moreover, we reexamine marginal stable circular orbits for a modified metric of a rapidly spinning black hole that has been recently proposed by Johannsen and Psaltis [Phys. Rev. D 83, 124015 (2011)]. We show that, for the Johannsen and Psaltis model, circular orbits that are stable against radial perturbations for some parameter region become unstable against zenithal perturbations. This suggests that the last circular orbit for this model may be larger than the innermost stable circular orbit.

The Hořava theory depends on several coupling constants. The kinetic term of its Lagrangian depends on one dimensionless coupling constant $\lambda$. For the particular value $\lambda =1/3$ the kinetic term becomes conformal invariant, although the full Lagrangian does not have this symmetry. For any value of $\lambda$ the nonprojectable version of the theory has second-class constraints that play a central role in the process of quantization. Here we study the complete nonprojectable theory, including the Blas-Pujolàs-Sibiryakov interacting terms, at the kinetic-conformal point $\lambda =1/3$. The generic counting of degrees of freedom indicates that this theory propagates the same physical degrees of freedom of general relativity. We analyze this point rigorously, taking into account all the $z=1$, 2, 3 terms that contribute to the action describing quadratic perturbations around the Minkowski spacetime. We show that the constraints of the theory and equations determining the Lagrange multipliers are strongly elliptic partial differential equations, an essential condition for a constrained phase-space structure in field theory. We show how their solutions lead to the two independent tensorial physical modes propagated by the theory. We also obtain the reduced Hamiltonian. These arguments strengthen the consistency of the theory. We find the restrictions on the space of coupling constants to ensure the positiveness of the reduced Hamiltonian. We obtain the propagator of the physical modes, showing that there are not ghosts and that the propagator effectively acquires the $z=3$ scaling for all physical degrees of freedom at the high-energy regime. By evaluating the superficial degree of divergence, taking into account the second-class constraints, we show that the theory is power-counting renormalizable. We analyze, in the path-integral formulation of the theory, the measure associated to the second-class constraints both in the canonical and the Lagrangian (foliation-preserving diffeomorphisms group-covariant) formalisms.