We investigate the topological properties of unquenched QCD on the basis of numerical results of simulations at fixed topological charge, recently reported by Borsanyi et al. We demonstrate that their results for the mean value of the chiral condensate at fixed topological charge are inconsistent with the analytical prediction of the large-volume expansion around the saddle point, and argue that the most plausible explanation for the failure of the saddle-point expansion is a vacuum energy density that is $\theta$-independent at high temperatures, but surprisingly not too high $(T\sim 2T_c)$, a result which would imply a vanishing topological susceptibility and the absence of all physical effects of the $U(1)$ axial anomaly at these temperatures. We also show that under a general assumption concerning the high-temperature phase of QCD, where the $SU(N_f{)}_A$ symmetry is restored, the analytical prediction for the chiral condensate at fixed topological charge is in very good agreement with the numerical results of Borsanyi et al., all effects of the axial anomaly should disappear, the topological susceptibility and all the $\theta$ derivatives of the vacuum energy density vanish, and the theory becomes $\theta$ independent at any $T>T_c$ in the infinite-volume limit.

We calculate the next-to-leading order QCD corrections to the excited charmonium ${\chi }_{cJ}$ associated with $W^{+}b$ production from top-quark decay. Our results show that detecting the ${\chi }_{c0}$ production from top-quark decay is very difficult, but the ${\chi }_{c1}$ and ${\chi }_{c2}$ productions have the potential to be detected at the LHC. If the prompt ${\chi }_{cJ}$ production from top-quark decay is really detected at the LHC, it will be useful not only for investigating $J/\psi$ production from top-quark decay but also for understanding the heavy quarkonium production mechanism.

We perform a comprehensive analysis of the strange-antistrange parton distribution function (PDF) asymmetry in the proton in the framework of chiral effective theory, including the full set of lowest-order kaon loop diagrams with off-shell and contact interactions, in addition to the usual on-shell contributions previously discussed in the literature. We identify the presence of $\delta$-function contributions to the $\overline{s}$ PDF at $x=0$, with a corresponding valencelike component of the $s$-quark PDF at larger $x$, which allows greater flexibility for the shape of $s-\overline{s}$. Expanding the moments of the PDFs in terms of the pseudoscalar kaon mass, we compute the leading nonanalytic behavior of the number and momentum integrals of the $s$ and $\overline{s}$ distributions, consistent with the chiral symmetry of QCD. We discuss the implications of our results for the understanding of the NuTeV anomaly and for the phenomenology of strange-quark PDFs in global QCD analysis.

Because Majorana fermions are their own antiparticles, their electric and magnetic dipole moments must vanish, leaving the anapole moment as their only static electromagnetic property. But the existence of induced dipole moments is not necessarily prohibited. Through a study of real Compton scattering, we explore the constraints that the Majorana fermion’s self-conjugate nature has on induced moments. In terms of the Compton amplitude, we find no constraints if the interactions are separately invariant under charge conjugation, parity, and time reversal. However, if the interactions are odd under parity and even under time reversal, then these contributions to the Compton amplitude must vanish. We employ a simple model to confirm these general findings via explicit calculation of the Majorana fermion’s polarizabilities. We then use these polarizabilities to estimate the cross section for $s$-wave annihilation of two Majorana fermions into photons. The cross section is larger than a naive estimate might suggest.

Electroweak (EW) corrections can be enhanced at high energies due to the soft or collinear radiation of virtual and real $W$ and $Z$ bosons that result in Sudakov-like corrections of the form ${\alpha }_W^l{\log }^n(Q^2/M_{W,Z}^2)$, where ${\alpha }_W=\alpha /(4\pi {\sin }^2{\theta }_W)$ and $n\le 2l-1$. The inclusion of EW corrections in predictions for hadron colliders is, therefore, especially important when searching for signals of possible new physics in distributions probing the kinematic regime $Q^2\gg M_V^2$. Next-to-leading order (NLO) EW corrections should also be taken into account when their size [$\mathcal{O}(\alpha )$] is comparable to that of QCD corrections at next-to-next-to-leading order (NNLO) [$\mathcal{O}({\alpha }_s^2)$]. To this end, we have implemented the NLO weak corrections to the neutral-current Drell-Yan process, top-quark pair production and dijet production in the parton-level Monte Carlo program MCFM. This enables a combined study with the corresponding QCD corrections at NLO and NNLO. We provide both the full NLO weak corrections and their Sudakov approximation since the latter is often used for a fast evaluation of weak effects at high energies and can be extended to higher orders. With both the exact and approximate results at hand, the validity of the Sudakov approximation can be readily quantified.

The induced magnetic moment that arises due to the propagation of neutrinos in a dispersive medium can affect the dynamics of the neutrino spin in an external electromagnetic field. In particular, it can cause a helicity flip of a massive neutrino in a magnetic field. In some astrophysical media, this helicity transition mechanism could be more effective than a similar process caused by the anomalous magnetic moment of the neutrino. If the neutrino energy is sufficiently high, the two helicity transition mechanisms mentioned above can compensate each other. Then a helicity flip in an external field will not occur. Calculations are carried out using both the methods of relativistic quantum mechanics and the quasiclassical Bargmann-Michel-Telegdi equation.

Nonstandard interactions (NSI) of neutrinos with matter can significantly alter neutrino flavor evolution in supernovae with the potential to impact explosion dynamics, nucleosynthesis, and the neutrinos signal. In this paper, we explore, both numerically and analytically, the landscape of neutrino flavor transformation effects in supernovae due to NSI and find a new, heretofore unseen transformation processes can occur. These new transformations can take place with NSI strengths well below current experimental limits. Within a broad swath of NSI parameter space, we observe symmetric and standard matter-neutrino resonances for supernovae neutrinos, a transformation effect previously only seen in compact object merger scenarios; in another region of the parameter space we find the NSI can induce neutrino collective effects in scenarios where none would appear with only the standard case of neutrino oscillation physics; and in a third region the NSI can lead to the disappearance of the high density Mikheyev-Smirnov-Wolfenstein resonance. Using a variety of analytical tools, we are able to describe quantitatively the numerical results allowing us to partition the NSI parameter according to the transformation processes observed. Our results indicate nonstandard interactions of supernova neutrinos provide a sensitive probe of beyond the Standard Model physics complementary to present and future terrestrial experiments.

We report a search for a dark vector gauge boson $U^{\prime }$ that couples to quarks in the decay chain $D^{*+}\to D^0{\pi }^{+},D^0\to K_S^0\eta ,\eta \to U^{\prime }\gamma$, $U^{\prime }\to {\pi }^{+}{\pi }^{-}$. No signal is found and we set a mass-dependent limit on the baryonic fine structure constant of ${10}^{-3}-{10}^{-2}$ in the $U^{\prime }$ mass range of 290 to $520\mathrm{MeV}/c^2$. This analysis is based on a data sample of $976{\mathrm{fb}}^{-1}$ collected by the Belle experiment at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider.

Knowledge of the neutrino flux produced by the Neutrinos at the Main Injector (NuMI) beamline is essential to the neutrino oscillation and neutrino interaction measurements of the MINERvA, $\mathrm{MINOS}+$, NOvA and MicroBooNE experiments at Fermi National Accelerator Laboratory. We have produced a flux prediction which uses all available and relevant hadron production data, incorporating measurements of particle production off of thin targets as well as measurements of particle yields from a spare NuMI target exposed to a 120 GeV proton beam. The result is the most precise flux prediction achieved for a neutrino beam in the one to tens of GeV energy region. We have also compared the prediction to in situ measurements of the neutrino flux and find good agreement.

We propose and study a holographic dual of the type-IIB superstring theory of ${\mathrm{AdS}}_5\times S^5$ in terms of the $\mathcal{N}=4$ superconformal Yang-Mills theory on ${\mathrm{dS}}_4$. We develop the bulk to boundary formalism for the computation of the correlation functions to a wide class of theories. We apply it to compute the two-point correlators in the particular duality under study and we find that they agree with the expected results in $dS$ conformal field theory. The gauge theory is expected to be UV finite and enjoy exact $SL(2,Z)$ strong-weak duality. As the string theory Green-Schwarz sigma model carries an infinite number of classically conserved charges, it also suggests that the superconformal Yang-Mills theory is integrable and deserves further studies.

We show that the equations of motion for (free) integer higher spin gauge fields can be formulated as twisted self-duality conditions on the higher spin curvatures of the spin-$s$ field and its dual. We focus on the case of four spacetime dimensions, but formulate our results in a manner applicable to higher spacetime dimensions. The twisted self-duality conditions are redundant and we exhibit a nonredundant subset of conditions, which have the remarkable property to involve only first-order derivatives with respect to time. This nonredundant subset equates the electric field of the spin-$s$ field (which we define) to the magnetic field of its dual (which we also define), and vice versa. The nonredundant subset of twisted self-duality conditions involve the purely spatial components of the spin-$s$ field and its dual, and also the components of the fields with one zero index. One can get rid of these gauge components by taking the curl of the equations, which does not change their physical content. In this form, the twisted self-duality conditions can be derived from a variational principle that involves prepotentials. These prepotentials are the higher spin generalizations of the prepotentials previously found in the spins 2 and 3 cases. The prepotentials have again the intriguing feature of possessing both higher spin diffeomorphism invariance and higher spin conformal geometry. The tools introduced in an earlier paper for handling higher spin conformal geometry turn out to be crucial for streamlining the analysis. In four spacetime dimensions where the electric and magnetic fields are tensor fields of the same type, the twisted self-duality conditions enjoy an $SO(2)$ electric-magnetic invariance. We explicitly show that this symmetry is an “off-shell symmetry” (i.e., a symmetry of the action and not just of the equations of motion). Remarks on the extension to higher dimensions are given.

We consider the self-interaction phenomenon in the framework of the Bopp-Podolsky electrodynamics. In the present paper, we obtain the self-interaction potential energy of a charge at rest for the spacetimes with topological defects of two types: for the axially symmetric spacetime of the straight cosmic string and the spherically symmetric global monopole spacetime. It is shown that the behavior of this expression depends essentially on the angular defect, in spite of the Bopp-Podolsky model parameter, which plays the role of a scale factor. In contrast with the usual Maxwell electrodynamics, the self-interaction energy for the Bopp-Podolsky electrodynamics appears to be finite everywhere and the standard renormalization procedure is not required.

We investigate the resonance interaction energy between two uniformly accelerated identical atoms, interacting with the scalar field or the electromagnetic field in the vacuum state, in the reference frame coaccelerating with the atoms. We assume that one atom is excited and the other is in the ground state and that they are prepared in their correlated symmetric or antisymmetric state. Using perturbation theory, we separate, at the second order in the atom-field coupling, the contributions of vacuum fluctuations and a radiation reaction field to the energy shift of the interacting system. We show that only the radiation reaction term contributes to the resonance interaction between the two atoms, while Unruh thermal fluctuations, related to the vacuum fluctuations contribution, do not affect the resonance interatomic interaction. We also show that the resonance interaction between two uniformly accelerated atoms, recently investigated in the comoving (locally inertial) frame, can be recovered in the coaccelerated frame, without the additional assumption of the Fulling-Davies-Unruh temperature for the quantum fields (as necessary for the Lamb shift, for example). This indicates, in the case considered, the equivalence between the coaccelerated frame and the locally inertial frame.

The Dirac quantization condition (DQC) for magnetic monopoles in noncommutative space-time is analyzed. For this a noncommutative generalization of the method introduced by Wu and Yang is considered; the effects of noncommutativity are analyzed using the Seiberg-Witten map and the corresponding deformed Maxwell’s equations are discussed. By using a perturbation expansion in the noncommutativity parameter $\theta$, we show first that the DQC remains unmodified up to the first and second order. This result is then generalized to all orders in the expansion parameter for a class of noncommutative electric currents induced by the Seiberg-Witten map; these currents reduce to the Dirac delta function in the commutative limit.

We apply the Noether procedure for gauging space-time symmetries to theories with Galilean symmetries, analyzing both massless and massive (Bargmann) realizations. It is shown that at the linearized level the Noether procedure gives rise to (linearized) torsional Newton-Cartan geometry. In the case of Bargmann theories the Newton-Cartan form $M_{\mu }$ couples to the conserved mass current. We show that even in the case of theories with massless Galilean symmetries it is necessary to introduce the form $M_{\mu }$ and that it couples to a topological current. Further, we show that the Noether procedure naturally gives rise to a distinguished affine (Christoffel type) connection that is linear in $M_{\mu }$ and torsionful. As an application of these techniques we study the coupling of Galilean electrodynamics to TNC geometry at the linearized level.

Atomic interferometry can be used to probe dark energy models coupled to matter. We consider the constraints coming from recent experimental results on models generalizing the inverse power law chameleons such as $f(R)$ gravity in the large curvature regime, the environmentally dependent dilaton and symmetrons. Using the tomographic description of these models, we find that only symmetrons with masses smaller than the dark energy scale can be efficiently tested. In this regime, the resulting constraints complement the bounds from the Eötwash experiment and exclude small values of the symmetron self-coupling.

We show that Schwarzschild black hole solutions in asymptotically anti-de Sitter (AdS) and de Sitter spaces may, up to a conformal factor, be reproduced in the framework of analogue gravity. The aforementioned derivation is performed using relativistic and nonrelativistic Bose-Einstein condensates. In addition, we demonstrate that the ($2+1$) planar AdS black hole can be mapped into the nonrelativistic acoustic metric. Given that AdS black holes are extensively employed in the gauge/gravity duality, we then comment on the possibility of studying the AdS/CFT correspondence and gravity/fluid duality from an analogue gravity perspective.

We study the thermodynamic properties of a black hole and the Hawking-Page phase transition in the asymptotically anti–de Sitter spacetime in the dilatonic Einstein-Gauss-Bonnet theory of gravitation. We show how the higher-order curvature terms can influence both the thermodynamic properties and the phase transition. We evaluate both heat capacity and free energy difference to determine the local and global thermodynamic stabilities, respectively. We find that the phase transition occurs from the thermal anti–de Sitter to a small spherical black hole geometry and occurs to a hyperbolic black hole geometry in the (dilatonic) Einstein-Gauss-Bonnet theory of gravitation unlike those in Einstein’s theory of gravitation.

Vacuum perturbations of the Kerr metric can be reconstructed from the corresponding perturbation in either of the two Weyl scalars ${\psi }_0$ or ${\psi }_4$, using a procedure described by Chrzanowski and others in the 1970s. More recent work, motivated within the context of self-force physics, extends the procedure to metric perturbations sourced by a particle in a bound geodesic orbit. However, the existing procedure leaves undetermined a certain stationary, axially symmetric piece of the metric perturbation. In the vacuum region away from the particle, this “completion” piece corresponds simply to mass and angular-momentum perturbations of the Kerr background, with amplitudes that are, however, a priori unknown. Here, we present and implement a rigorous method for finding the completion piece. The key idea is to impose continuity, off the particle, of certain gauge-invariant fields constructed from the full (completed) perturbation, in order to determine the unknown amplitude parameters of the completion piece. We implement this method in full for bound (eccentric) geodesic orbits in the equatorial plane of the Kerr black hole. Our results provide a rigorous underpinning of recent results by Friedman et al. for circular orbits and extend them to noncircular orbits.

We introduce an analogue model for a nonglobally hyperbolic spacetime in terms of a two-dimensional fluid. This is done by considering the propagation of sound waves in a radial flow with constant velocity. We show that the equation of motion satisfied by sound waves is the wave equation on ${\mathrm{AdS}}_2\times S^1$. Since this spacetime is not globally hyperbolic, the dynamics of the Klein-Gordon field is not well defined until boundary conditions at the spatial boundary of ${\mathrm{AdS}}_2$ are prescribed. On the analogue model end, those extra boundary conditions provide an effective description of the point source at $r=0$. For waves with circular symmetry, we relate the different physical evolutions to the phase difference between ingoing and outgoing scattered waves. We also show that the fluid configuration can be stable or unstable depending on the chosen boundary condition.