We present results of a search for a possible signal from small scale solar transient events (such as flares and interplanetary shocks) as well as possible counterparts to gamma-ray burst (GRB) observed simultaneously by the Tupi muon telescope (Niteroi, Brazil, $22.9°\mathrm{S}$, $43.2°\mathrm{W}$, 3 m above sea level) and the Pierre Auger Observatory surface detectors (Malargue, Argentina, $69.3°\mathrm{S}$, $35.3°\mathrm{W}$, altitude 1400 m). Both cosmic ray experiments are located inside the South Atlantic Anomaly region. Our analysis of several examples shows similarities in the behavior of the counting rate of low energy (above 100 MeV) particles in association with the solar activity (solar flares and interplanetary shocks). We also report an observation by the Tupi experiment of the enhancement of muons at ground level with a significance $8\sigma$ in the 1-sec binning counting rate (raw data) in close time coincidence (T-184 sec) with the Swift-BAT GRB110928B ($\mathrm{\text{trigger}}=504307$), according to the GRB Coordinate Network report. At the same time this event was not included in the Swift-XRT products for GRBs. The GRB 110928B coordinates are in the field of view of the vertical Tupi telescope, and the burst was close to the MAXI source J1836-194. The 5-min muon counting rate in the vertical Tupi telescope as well as publicly available data from Auger (15 min averages of the scaler rates) show small peaks above the background fluctuations at the time following the Swift-BAT GRB 110928B trigger. In accordance with the long duration trigger, this signal can possibly suggest a long GRB, with a precursor narrow peak at T-184 sec, or a transient Galactic source.

Light sterile neutrinos have been introduced as an explanation for a number of oscillation signals at $\Delta m^2\sim 1{\mathrm{eV}}^2$. Neutrino oscillations at relatively short baselines provide a probe of these possible new states. This paper describes an accelerator-based experiment using neutral current coherent neutrino-nucleus scattering to strictly search for active-to-sterile neutrino oscillations. This experiment could, thus, definitively establish the existence of sterile neutrinos and provide constraints on their mixing parameters. A cyclotron-based proton beam can be directed to multiple targets, producing a low-energy pion and muon decay-at-rest neutrino source with variable distance to a single detector. Two types of detectors are considered: a germanium-based detector inspired by the SuperCDMS design and a liquid argon detector inspired by the proposed CLEAR experiment.

We test Einstein gravity using cosmological observations of both expansion and structure growth, including the latest data from supernovae (Union2.1), cosmic microwave background (WMAP7), weak lensing (CFHTLS) and the peculiar velocity of galaxies (WiggleZ). We fit modified gravity parameters of the generalized Poisson equations simultaneously with the effective equation of state for the background evolution, exploring the covariances and model dependence. The results show that general relativity is a good fit to the combined data. Using a Padé approximant form for the gravity deviations accurately captures the time and scale dependence for theories like $f(R)$ and DGP gravity, and weights high and low redshift probes fairly. For current observations, cosmic growth and expansion can be fit simultaneously with little degradation in accuracy, while removing the possibility of bias from holding one aspect fixed.

We find exact nonstatic null-dust solutions in metric $f(R)$ gravity, imposed by the constant scalar curvature, which describes the gravitational collapse of null dust in (anti-)de Sitter [(A)dS] higher-dimensional (HD) background. The situation where a null dust injects into the initially HD-(A)dS spacetime leads to a naked singularity from gravitational collapse in HD-$f(R)$ gravity, violating cosmic censorship conjecture. Further, we find exact null-dust solutions to constant curvature imposed non-Abelian $f(R)$ Yang-Mills gauge theory by employing the Wu-Yang ansatz in four dimensions. This generates an identical geometry as one would expect for charge null dust in the Abelian $f(R)$ Maxwell theory, i.e., precisely the charged-Vaidya-(A)dS corresponding to Yang-Mills gauge charge. The four-dimensional charged null-dust solutions in the $f(R)$ Maxwell theory are also, separately, derived.

The unitary crisis for black holes indicates an apparent need to modify local quantum field theory. This paper explores the idea that quantum mechanics and, in particular, unitarity are fundamental principles, but at the price of familiar locality. Thus, one should seek to parameterize unitary evolution, extending the field theory description of black holes, such that their quantum information is transferred to the external state. This discussion is set in a broader framework of unitary evolution acting on Hilbert spaces comprising subsystems. Here, various constraints can be placed on the dynamics, based on quantum information-theoretic and other general physical considerations, and one can seek to describe dynamics with minimal departure from field theory. While usual spacetime locality may not be a precise concept in quantum gravity, approximate locality seems an important ingredient in physics. In such a Hilbert-space approach an apparently coarser form of localization can be described in terms of tensor decompositions of the Hilbert space of the complete system. This suggests a general framework in which to seek a consistent description of quantum gravity, and approximate emergence of spacetime. Other possible aspects of such a framework—in particular, symmetries—are briefly discussed.

The Nambu–Jona-Lasinio–jet model provides a framework for calculating fragmentation functions without the introduction of ad hoc parameters. We develop the Nambu–Jona-Lasinio–jet model to investigate dihadron fragmentation functions (DFFs) of the form $D_q^{h_1,h_2}(z_1,z_2)$. Here we studied DFFs for $q\to \{{\pi }^{+}{\pi }^{-}\}$, $\{{\pi }^{+}{K}^{-}\}$ and $\{K^{+}{K}^{-}\}$ with $q=u$, $d$, $s$. The driving terms, which represent the probability of one of the hadrons being emitted in the first emission step of the quark-jet hadronization picture, dominate the solutions of the DFFs where either $z_1$ or $z_2$ is large, and $z_1$ ($z_2$) is the light-cone momentum fraction of the emitted hadron, $h_1$ ($h_2$). The higher order terms, which represent the probability of neither of the hadrons being emitted in the first emission step of the quark-jet, become more significant as $z_1$ ($z_2$) is lowered. Finally, we present a sample result for QCD evolution of DFFs, that significantly modify the model solutions when evolved to typical experimental scale of $4{\mathrm{GeV}}^2$.

We discuss a possible dependence of the chiral magnetic effect (CME) on the elliptic flow coefficient $v_2$. We first study this in a hydrodynamic model for a static anisotropic plasma with multiple anomalous $U(1)$ currents. In the case of two charges, one axial and one vector, the CME formally appears as a first-order transport coefficient in the vector current. We compute this transport coefficient and show its dependence on $v_2$. We also determine the CME coefficient from first-order corrections to the dual anti-de Sitter background using the fluid-gravity duality. For small anisotropies, we find numerical agreement with the hydrodynamic result.

The Zariski quantization is one of the strong candidates for a quantization of the Nambu-Poisson bracket. In this paper, we reinterpret the Zariski quantization and study physical properties of it. Here, we do not treat the Zariski quantization as a deformation quantization. Instead, we perform a path integral of a theory after the Zariski quantization, which only deforms an action. As a result, we find that second quantized field theories are obtained by performing the Zariski quantization and path-integrals of perturbative superstring and supermembrane theories. Actually, we find flat directions, which indicate that the Zariski quantized theories describe many-body systems. We also find that pair creations and annihilations occur among the many bodies introduced by the Zariski quantization, by studying a simple model. Moreover, the Zariski quantization preserves supersymmetries of the superstring and supermembrane theories.

In the framework of the gauge invariant approach involving Stueckelberg and auxiliary fields, a totally symmetric arbitrary spin anomalous conformal current and shadow field in flat space-time of dimension greater than or equal to 4 are studied. Gauge invariant differential constraints for such anomalous conformal current and shadow field and realization of global conformal symmetries are obtained. A gauge invariant two-point vertex of the arbitrary spin anomalous shadow field is also obtained. In the Stueckelberg gauge frame, the two-point gauge invariant vertex becomes the standard two-point vertex of CFT. A light-cone gauge two-point vertex of the arbitrary spin anomalous shadow field is derived. The AdS/CFT correspondence for arbitrary spin anomalous conformal current and shadow field and the respective normalizable and non-normalizable modes of massive arbitrary spin AdS field is studied. The AdS field is considered in modified de Donder gauge which simplifies considerably the study of AdS/CFT correspondence. We show that on-shell leftover gauge symmetries of bulk massive field are related to gauge symmetries of boundary anomalous conformal current and shadow field, while the modified de Donder gauge condition for a bulk massive field is related to differential constraints for boundary anomalous conformal current and shadow field.

In our continued efforts of matching full string computations with the corresponding effective field theory computations, we evaluate string theory correlators in closed forms. In particular, we consider a correlator between three super Yang-Mills vertex operators and one Ramond-Ramond $C$-field vertex operator: $⟨V_C{V}_{\varphi }{V}_A{V}_A⟩$. We show that the infinite number of massless poles of this amplitude can be reproduced by the Born-Infeld action, the Wess-Zumino terms, and their higher derivative corrections. More specifically, we find, up to an on-shell ambiguity, two scalar field and two gauge field couplings to all orders in ${\alpha }^{\prime }$ such that the infinite number of massless poles of the field theory amplitude exactly match the infinite number of massless poles of the S-matrix elements of $⟨V_C{V}_{\varphi }{V}_A{V}_A⟩$. We comment on the close intertwinedness of an open string and a closed string that must be behind the matching.

We treat the probability distributions for quadratic quantum fields, averaged with a Lorentzian test function, in four-dimensional Minkowski vacuum. These distributions share some properties with previous results in two-dimensional spacetime. Specifically, there is a lower bound at a finite negative value, but no upper bound. Thus arbitrarily large positive energy density fluctuations are possible. We are not able to give closed form expressions for the probability distribution, but rather use calculations of a finite number of moments to estimate the lower bounds, the asymptotic forms for large positive argument, and possible fits to the intermediate region. The first 65 moments are used for these purposes. All of our results are subject to the caveat that these distributions are not uniquely determined by the moments. We apply the asymptotic form of the electromagnetic energy density distribution to estimate the nucleation rates of black holes and of Boltzmann brains.

We extend our previous work on a derivative expansion for the Casimir energy, to the case of the electromagnetic field coupled to two thin, imperfect mirrors. The latter are described by means of vacuum polarization tensors localized on the mirrors. We apply the results so obtained to compute the first correction to the proximity force approximation to the static Casimir effect.

Understanding the consequences of the $E_{7(7)}$ duality on the UV properties of $\mathcal{N}=8$ supergravity requires unravelling when and how duality-covariant actions can be constructed so as to accommodate duality-invariant counterterms. For nonsupersymmetric Abelian gauge theories exhibiting $U(1)$-duality, with and without derivative couplings, it was shown that such a covariant construction is always possible. In this paper we describe a similar procedure for the construction of covariant nonlinear deformations of $U(1)$-duality invariant theories in the presence of rigid $\mathcal{N}=2$ supersymmetry. This is a concrete step towards studying the interplay of duality and extended supersymmetry.

The effect of an exponentially decaying magnetic field on the dynamics of Dirac fermions in $3+1$ dimensions is explored. The spatially decaying magnetic field is assumed to be aligned in the third direction, and is defined by $\mathbf{B}(x)=B(x){\mathbf{e}}_z$, with $B(x)=B_0{e}^{-\xi x/{\ell }_B}$. Here, $\xi$ is a dimensionless damping factor and ${\ell }_B=(e{B}_0{)}^{-1/2}$ is the magnetic length. As it turns out, the energy spectrum of fermions in this inhomogeneous magnetic field can be analytically determined using the Ritus method. Assuming the magnetic field to be strong, the chiral condensate and the local electric current correlation function are computed in the lowest Landau level (LLL) approximation and the results are compared with those arising from a strong homogeneous magnetic field. Although the constant magnetic field $B_0$ can be reproduced by taking the limit of $\xi \to 0$ and/or $x\to 0$ from $B(x)$, these limits turn out to be singular, especially once the quantum corrections are taken into account.

We perform fully nonlinear numerical simulations of charged-black-hole collisions, described by the Einstein-Maxwell equations, and contrast the results against analytic expectations. We focus on head-on collisions of nonspinning black holes, starting from rest and with the same charge-to-mass ratio, $Q/M$. The addition of charge to black holes introduces a new interesting channel of radiation and dynamics, most of which seem to be captured by Newtonian dynamics and flat-space intuition. The waveforms can be qualitatively described in terms of three stages: (i) an infall phase prior to the formation of a common apparent horizon; (ii) a nonlinear merger phase that corresponds to a peak in gravitational and electromagnetic energy; (iii) the ringdown marked by an oscillatory pattern with exponentially decaying amplitude and characteristic frequencies that are in good agreement with perturbative predictions. We observe that the amount of gravitational-wave energy generated throughout the collision decreases by about 3 orders of magnitude as the charge-to-mass ratio $Q/M$ is increased from 0 to 0.98. We interpret this decrease as a consequence of the smaller accelerations present for larger values of the charge. In contrast, the ratio of energy carried by electromagnetic to gravitational radiation increases, reaching about 22% for the maximum $Q/M$ ratio explored, which is in good agreement with analytic predictions.

In this paper we revisit a gauge theory of supergravity, where the tetrad, the spin $3/2$ field and the spin connection are identified with components of the gauge field. This theory naturally incorporates a cosmological constant term. Furthermore, when adding the topological $\theta$-term, as in the Yang-Mills theory, an analogue of the Immirzi term for $\mathcal{N}=1$ supergravity is obtained.

We perform a nonperturbative analysis to the Hamiltonian constraint of the lowest-order effective action of the complete Hořava theory, which includes a $({\partial }_i\ln N{)}^2$ term in the Lagrangian. We cast this constraint as a partial differential equation for $N$ and show that the solution exists and is unique under a condition of positivity for the metric and its conjugate momentum. We interpret this condition as the analog of the positivity of the spatial scalar curvature in general relativity. From the analysis we extract several general properties of the solution for $N$: an upper bound on its absolute value and its asymptotic behavior. In particular, we find that the asymptotic behavior is different from that of general relativity, which has consequences on the evolution of the initial data and the calculus of variations. Similarly, we proof the existence and uniqueness of the solution of the equation for the Lagrange multiplier of the theory. We also find a relationship between the expression of the energy and the solution of the Hamiltonian constraint. Using it we prove the positivity of the energy of the effective action under consideration. Minkowski spacetime is obtained from Hořava theory at minimal energy.

We discuss a Brans-Dicke model with a cosmological constant, a negative value of the $w$ parameter, and an arbitrary (in general nonvanishing) scale factor at the big bang. The Friedmann equations for a flat universe are considered. The current observational values for Hubble constant $H_0$ and deceleration parameter $q_0$ play the role of initial conditions. We follow the approach of Uehara and Kim in order to solve field equations analytically. In K. Uehara and C. W. Kim [Phys. Rev. D 26, 2575 (1982)] only positive values of $w$ were considered; we extend the study to a complete set of possible $w$ values. Our main result is that the scale factor (during its evolution back in time direction) may not vanish, unlike in the standard $\Lambda \mathrm{CDM}$ case. In other words, the considered model demonstrates a cosmological bounce instead of the initial singularity. The famous formula (24), that leads to the bounce, is valid only for the dust-filled universe with $p=0$ and, therefore, is not adequate for the early universe hot stage when the bounce happens. So, our results are qualitative in nature and must be used to obtain initial values for the hot stage of the Universe.

We define the angular momentum at null infinity in higher dimensions. The asymptotic symmetry at null infinity becomes the Poincaré group in higher dimensions. This fact implies that the angular momentum can be defined without any ambiguities such as the supertranslation in four dimensions. Indeed we can show that the angular momentum in our definition is transformed covariantly with respect to the Poincaré group.