We investigate the isovector axial vector and pseudoscalar form factors of $\mathrm{\Delta }$ baryon by employing light-cone QCD sum rules. Numerical calculations show that the form factors can be well fitted by the exponential form. We make a comparison with the predictions of lattice QCD, chiral perturbation theory and quark model.

The quark potential model for mesons and its extension for hybrid mesons are used to study the effects of radial excitations on the masses, sizes, and radial wave functions at the origin for conventional and hybrid charmonium mesons. These nonrelativistic quark potential models are also used to calculate the $E1$ and $M1$ radiative partial widths for conventional meson to meson and hybrid to hybrid transitions. Relativistic corrections in masses and radiative widths are calculated by applying leading-order perturbation theory. To numerically solve the required Schrödinger equation for the radial wave functions, to be relativistically improved, we use the shooting method. We compare our results with the experimentally observed and theoretically predicted results of the other models. Our results have implications for scalar form factors, energy shifts, and polarizabilities of conventional and hybrid mesons. The comparison of masses of conventional and hybrid charmonium mesons with the masses of recently discovered $XYZ$ particles is also discussed. Thus, our results can help in experimentally recognizing hybrid mesons.

We compute the spin asymmetry of the muon decay $\mu \to e{\overline{\nu }}_e{\nu }_{\mu }$ through $\mathcal{O}({\alpha }^2)$ in perturbative QED. These two-loop corrections are about a factor 5 (20) smaller than the current statistical (systematic) uncertainty of the most precise measurement, performed by the TWIST Collaboration. We point out that at $\mathcal{O}({\alpha }^2)$ the asymmetry requires a careful definition due to multilepton final states, and we suggest to use familiar QCD techniques to define it in an infrared safe way. We find that the TWIST measurement of the asymmetry is in excellent agreement with the Standard Model.

In this paper we analyze the neutrinoless double beta decay predictions in some scenarios with admixture of pseudo-Dirac and Majorana neutrinos in the 3 and $3+1$ neutrino frameworks. We found that some of the cases can be falsifiable in near-term and future generation of neutrinoless double beta decay experiments even for the normal neutrino mass hierarchy. In the $3+1$ framework we consider the sterile neutrino with a mass of the order of 1 eV. The complementarity between cosmological constraints and the future sensitivity for the next generations of the neutrinoless double beta decay searches is exploited.

The Bose-ghost propagator has been proposed as a carrier of the confining force in Yang-Mills theories in minimal Landau gauge. We present the first numerical evaluation of this propagator, using lattice simulations for the SU(2) gauge group in the scaling region. Our data are well described by a simple fitting function, which is compatible with an infrared-enhanced Bose-ghost propagator. This function can also be related to a massive gluon propagator in combination with an infrared-free (Faddeev-Popov) ghost propagator. Since the Bose-ghost propagator can be written as the vacuum expectation value of a BRST-exact quantity and should therefore vanish in a BRST-invariant theory, our results provide the first numerical manifestation of BRST-symmetry breaking due to restriction of gauge-configuration space to the Gribov region.

We study giant magnon solutions for strings moving on a deformed ${AdS}_3\times S^3$ background. We impose a conformal gauge on the Polyakov action and proceed with solving the Virasoro constraints. The expressions of the conserved charge $J$ and the energy of a single magnon excitation are then computed. Then we determine the dispersion relation of a giant magnon in the infinite $J$ limit configuration and we find that for $\kappa =0$ it reduces to the celebrated Hofman-Maldacena dispersion relation.

Accretion of fields by black holes is a subject of great interest in physics. It is known that accretion plays a fundamental role in active galactic nuclei and in the evolution of black holes. Accretion of fundamental fields is often related to the study of absorption cross section. Basically all black holes for which absorption of fields has been studied so far present singularities. However, even within general relativity, it is possible to construct regular black holes: objects with event horizons but without singularities. Many physically motivated regular black hole solutions have been proposed in the past years, demanding the understanding of their absorption properties. We study the absorption of planar massless scalar waves by Bardeen regular black holes. We compare the absorption cross section of Bardeen and Reissner–Nordström black holes, showing that the former always have a bigger absorption cross section for fixed values of the field frequency and of the normalized black hole charge. We also show that it is possible for a Bardeen black hole to have the same high-frequency absorption cross section of a Reissner–Nordström black hole. Our results suggest that, in mid-to-high-frequency regimes, regular black holes can have compatible properties with black holes with singularities, as far as absorption is concerned.

We investigate the implications for inflation of the detection of $B$-modes polarization in the cosmic microwave background by BICEP2. We show that the hypothesis of the primordial origin of the measurement is favored only by the first four band powers, while the others would prefer unreasonably large values of the tensor-to-scalar ratio. Using only those four band powers, we carry out a complete analysis in the cosmological and inflationary slow-roll parameter space using the BICEP2 polarization measurements alone and extract the Bayesian evidences and complexities for all the Encyclopædia Inflationaris models. This allows us to determine the most probable and simplest BICEP2 inflationary scenarios. Although this list contains the simplest monomial potentials, it also includes many other scenarios, suggesting that focusing model building efforts on large field models only is unjustified at this stage. We demonstrate that the sets of inflationary models preferred by Planck alone and BICEP2 alone are almost disjoint, indicating a clear tension between the two data sets. We address this tension with a Bayesian measure of compatibility between BICEP2 and Planck. We find that for models favored by Planck the two data sets tend to be incompatible, whereas there is moderate evidence of compatibility for the BICEP2 preferred models. As a result, it would be premature to draw any conclusion on the best Planck models, such as Starobinsky and/or Kähler moduli inflation. For the subset of scenarios not exhibiting data sets incompatibility, we update the evidences and complexities using both data sets together.

In a previous paper [M. E. Gusakov, A. I. Chugunov, and E. M. Kantor, Phys. Rev. Lett. 112, 151101 (2014)], we introduced a new scenario that explains the existence of rapidly rotating warm neutron stars (NSs) observed in low-mass x-ray binaries (LMXBs). Here it is described in more detail. The scenario takes into account the interaction between superfluid inertial modes and the normal (quadrupole) $m=2$ $r$ mode, which can be driven unstable by the Chandrasekhar-Friedman-Schutz (CFS) mechanism. This interaction can only occur at some fixed “resonance” stellar temperatures; it leads to formation of the “stability peaks” which stabilize a star in the vicinity of these temperatures. We demonstrate that a NS in LMXB spends a substantial fraction of time on the stability peak, that is, in the region of stellar temperatures and spin frequencies that has been previously thought to be CFS unstable with respect to excitation of $r$ modes. We also find that the spin frequencies of NSs are limited by the CFS instability of normal (octupole) $m=3$ $r$ mode rather than by $m=2$ $r$ mode. This result agrees with the predicted value of the cutoff spin frequency $\sim 730\mathrm{Hz}$ in the spin distribution of accreting millisecond x-ray pulsars. In addition, we analyze evolution of a NS after the end of the accretion phase and demonstrate that millisecond pulsars can be born in LMXBs within our scenario. Besides millisecond pulsars, our scenario also predicts a new class of LMXB descendants—hot and rapidly rotating nonaccreting NSs (“hot widows”/HOFNARs). Further comparison of the proposed theory with observations of rotating NSs can impose new important constraints on the properties of superdense matter.

LOPES is a digital radio interferometer located at Karlsruhe Institute of Technology (KIT), Germany, that measures radio emission from extensive air showers at MHz frequencies in coincidence with KASCADE-Grande. In this article, we explore a method (slope method) that leverages the slope of the measured radio lateral distribution to reconstruct crucial attributes of primary cosmic rays. First, we present an investigation of the method on the basis of pure simulations. Second, we directly apply the slope method to LOPES measurements. Applying the slope method to simulations, we obtain uncertainties on the reconstruction of energy and depth of shower maximum (${\mathrm{X}}_{\max }$) of 13% and $50\mathrm{g}/{\mathrm{cm}}^2$, respectively. Applying it to LOPES measurements, we are able to reconstruct energy and ${\mathrm{X}}_{\max }$ of individual events with upper limits on the precision of 20%–25% for the primary energy and $95\mathrm{g}/{\mathrm{cm}}^2$ for ${\mathrm{X}}_{\max }$, despite strong human-made noise at the LOPES site.

It has recently been shown that dark-matter annihilation to bottom quarks provides a good fit to the Galactic Center gamma-ray excess identified in the Fermi-LAT data. In the favored dark-matter mass range $m\sim 30–40\mathrm{GeV}$, achieving the best-fit annihilation rate $\sigma v\sim 5\times {10}^{-26}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ with perturbative couplings requires a sub-TeV mediator particle that interacts with both dark matter and bottom quarks. In this paper, we consider the minimal viable scenarios in which a Standard Model singlet mediates $s$-channel interactions only between dark matter and bottom quarks, focusing on axial-vector, vector, and pseudoscalar couplings. Using simulations that include on-shell mediator production, we show that existing sbottom searches currently offer the strongest sensitivity over a large region of the favored parameter space explaining the gamma-ray excess, particularly for axial-vector interactions. The 13 TeV LHC will be even more sensitive; however, it may not be sufficient to fully cover the favored parameter space, and the pseudoscalar scenario will remain unconstrained by these searches. We also find that direct-detection constraints, induced through loops of bottom quarks, complement collider bounds to disfavor the vector-current interaction when the mediator is heavier than twice the dark-matter mass. We also present some simple models that generate pseudoscalar-mediated annihilation predominantly to bottom quarks.

Radiative flavor models where the hierarchies of Standard Model (SM) fermion masses and mixings are explained via loop corrections are elegant ways to solve the SM flavor puzzle. Here we build such a model in the context of mini-split supersymmetry (SUSY) where both flavor and SUSY breaking occur at a scale of 1000 TeV. This model is consistent with the observed Higgs mass, unification, and dark matter as a weakly interacting massive particle. The high scale allows large flavor mixing among the sfermions, which provides part of the mechanism for radiative flavor generation. In the deep UV, all flavors are treated democratically, but at the SUSY-breaking scale, the third, second, and first generation Yukawa couplings are generated at tree level, one loop, and two loops, respectively. Save for one, all the dimensionless parameters in the theory are $\mathcal{O}(1)$, with the exception being a modest and technically natural tuning that explains both the smallness of the bottom Yukawa coupling and the largeness of the Cabibbo angle.

We study Higgs boson production in exclusive jet bins at possible future 33 and 100 TeV proton-proton colliders. We compare the cross sections obtained using fixed-order perturbation theory with those obtained by also resumming large logarithms induced by the jet-binning in the gluon-fusion and associated production channels. The central values obtained by the best-available fixed-order predictions differ by 10%–20% from those obtained after including resummation over the majority of phase-space regions considered. Additionally, including the resummation dramatically reduces the residual scale variation in these regions, often by a factor of two or more. We further show that in several new kinematic regimes that can be explored at these high-energy machines, the inclusion of resummation improvement is mandatory.

The canonical formulation for an action containing a scalar curvature squared term ($R^2$) in arbitrary dimension has been performed in a Robertson-Walker minisuperspace model. The quantum dynamics does not alter significantly from the same in four dimensions, while the continuity equation picks up a particular operator-ordering index. The classical solution is also at par with the one presented by Starobinsky for $k=0$ and matches with the extremum of the effective potential. Semiclassical approximation peaks around the classical solution.

We study entanglement in thermofield double states of strongly coupled conformal field theories by analyzing two-sided Reissner-Nordström solutions in anti–de Sitter space. The central object of study is the mutual information between a pair of regions, one on each asymptotic boundary of the black hole. For large regions the mutual information is positive and for small ones it vanishes; we compute the critical length scale, which goes to infinity for extremal black holes, of the transition. We also generalize the butterfly effect of Shenker and Stanford [J. High Energy Phys. 03 (2014) 067] to a wide class of charged black holes, showing that mutual information is disrupted upon perturbing the system and waiting for a time of order $\log E/\delta E$ in units of the temperature. We conjecture that the parametric form of this time scale is universal.

We derive covariant equations for a system of two quarks and two antiquarks where the effect of quark-antiquark annihilation is taken into account. In our approach, only pairwise interactions are retained, while all possibilities of overcounting are excluded by (i) keeping terms in the kernel that are consistent with a meson-meson and diquark-antidiquark substructure, and (ii) introducing four-body equations with a novel structure that specifically avoids the generation of overcounted terms. The resulting tetraquark bound state equations are given for the case of general two-body interactions, and for the specific case of separable interactions that lead to a description of the tetraquark in terms of meson-meson and diquark-antidiquark degrees of freedom where the effects of quark-antiquark annihilation are included. The inclusion of $2q2\overline{q}$- and $q\overline{q}$-channel coupling in our approach enables a wide variety of applications of our equations to other processes within the $2q2\overline{q}$ system, and to other two-particle plus two-antiparticle systems.

We derive the relativistic factor for splitting of the $g$-factors of a fermion and its antifermion partner, which is important for placing constraints on dimension-five, $CPT$-odd and Lorentz-invariance-violating interactions from experiments performed in a cyclotron. From existing data, we extract limits ($1\sigma$) on the coupling strengths of the temporal component, $f^0$, of a background field (including the field amplitude), which is responsible for such $g$-factor splitting, with an electron, proton, and muon: $|f_e^0|<2.3\times 10^{-12}{\mu }_{\mathrm{B}}$, $|f_p^0|<4\times 10^{-9}{\mu }_{\mathrm{B}}$, and $|f_{\mu }^0|<8\times 10^{-11}{\mu }_{\mathrm{B}}$, respectively, in the laboratory frame (${\mu }_{\mathrm{B}}$ is the Bohr magneton). From existing data, we also extract limits on the coupling strengths of the spatial components, $d^{\perp }$, of related dimension-five interactions of a background field with an electron, proton, neutron, and muon: $|d_e^{\perp }|\lesssim 10^{-9}{\mu }_{\mathrm{B}}$, $|d_p^{\perp }|\lesssim 10^{-9}{\mu }_{\mathrm{B}}$, $|d_n^{\perp }|\lesssim 10^{-10}{\mu }_{\mathrm{B}}$, and $|d_{\mu }^{\perp }|\lesssim 10^{-9}{\mu }_{\mathrm{B}}$, respectively, in the laboratory frame.

Bayesian parameter estimation on gravitational waves from compact-binary coalescences (CBCs) typically requires millions of template waveform computations at different values of the parameters describing the binary. Sampling techniques such as Markov chain Monte Carlo and nested sampling evaluate likelihoods and, hence, compute template waveforms, serially; thus, the total computational time of the analysis scales linearly with that of template generation. Here we address the issue of rapidly computing the likelihood function of CBC sources with nonspinning components. We show how to efficiently compute the continuous likelihood function on the three-dimensional subspace of parameters on which it has a nontrivial dependence—the chirp mass, symmetric mass ratio and coalescence time—via interpolation. Subsequently, sampling this interpolated likelihood function is a significantly cheaper computational process than directly evaluating the likelihood; we report improvements in computational time of two to three orders of magnitude while keeping likelihoods accurate to $\lesssim 0.025\%$. Generating the interpolant of the likelihood function over a significant portion of the CBC mass space is computationally expensive but highly parallelizable, so the wall time can be very small relative to the time of a full parameter-estimation analysis.

Shape dynamics is a reformulation of general relativity, locally equivalent to Einstein’s theory, in which the refoliation invariance of the older theory is traded for local scale invariance. Shape dynamics is here derived in a formulation related to the Ashtekar variables by beginning with a modification of the Plebanski action. The constraints of shape dynamics and their algebra are reproduced in terms of these new variables.