Working with a pion mass $m_{\pi }\approx 150\mathrm{MeV}$, we study $\pi \pi$ and $K\pi$ scattering using two flavors of nonperturbatively improved Wilson fermions at a lattice spacing $a\approx 0.071\mathrm{fm}$. Employing two lattice volumes with linear spatial extents of $N_s=48$ and $N_s=64$ points and moving frames, we extract the phase shifts for $p$-wave $\pi \pi$ and $K\pi$ scattering near the $\rho$ and $K^{*}$ resonances. Comparing our results to those of previous lattice studies, that used pion masses ranging from about 200 MeV up to 470 MeV, we find that the coupling $g_{\rho \pi \pi }$ appears to be remarkably constant as a function of $m_{\pi }$.

We investigate finite-volume effects in the hadronic vacuum polarization, with an eye toward the corresponding systematic error in the muon anomalous magnetic moment. We consider both recent lattice data as well as lowest-order, finite-volume chiral perturbation theory, in order to get a quantitative understanding. Even though leading-order chiral perturbation theory does not provide a good description of the hadronic vacuum polarization, it turns out that it gives a good representation of finite-volume effects. We find that finite-volume effects cannot be ignored when the aim is a few percent level accuracy for the leading-order hadronic contribution to the muon anomalous magnetic moment, even when using ensembles with $m_{\pi }L\gtrsim 4$ and $m_{\pi }\sim 200\mathrm{MeV}$.

A search for evidence of particle dark matter (DM) and unparticle production at the LHC has been performed using events containing two charged leptons, consistent with the decay of a $Z$ boson, and large missing transverse momentum. This study is based on data collected with the CMS detector corresponding to an integrated luminosity of $19.7{\mathrm{fb}}^{-1}$ of $pp$ collisions at the LHC at a center-of-mass energy of 8 TeV. No significant excess of events is observed above the number expected from the standard model contributions. The results are interpreted in terms of 90% confidence level limits on the DM-nucleon scattering cross section, as a function of the DM particle mass, for both spin-dependent and spin-independent scenarios. Limits are set on the effective cutoff scale $\mathrm{\Lambda }$, and on the annihilation rate for DM particles, assuming that their branching fraction to quarks is 100%. Additionally, the most stringent 95% confidence level limits to date on the unparticle model parameters are obtained.

In this article we provide a multitrace analysis of the theory of noncommutative ${\mathrm{\Phi }}^4$ in two dimensions on the fuzzy sphere ${\mathbf{S}}_{N,\mathrm{\Omega }}^2$, and on the Moyal-Weyl plane ${\mathbf{R}}_{\theta ,\mathrm{\Omega }}^2$, with a nonzero harmonic oscillator term added. The double-trace matrix model symmetric under $M\to -M$ is solved in closed form. An analytical prediction for the disordered-to-nonuniform-ordered phase transition and an estimation of the triple point, from the termination point of the critical boundary, are derived and compared with previous Monte Carlo measurement.

We introduce a class of permutation centralizer algebras which underly the combinatorics of multimatrix gauge-invariant observables. One family of such noncommutative algebras is parametrized by two integers. Its Wedderburn-Artin decomposition explains the counting of restricted Schur operators, which were introduced in the physics literature to describe open strings attached to giant gravitons and were subsequently used to diagonalize the Gaussian inner product for gauge invariants of two-matrix models. The structure of the algebra, notably its dimension, its center and its maximally commuting subalgebra, is related to Littlewood-Richardson numbers for composing Young diagrams. It gives a precise characterization of the minimal set of charges needed to distinguish arbitrary matrix gauge invariants, which are related to enhanced symmetries in gauge theory. The algebra also gives a star product for matrix invariants. The center of the algebra allows efficient computation of a sector of multimatrix correlators. These generate the counting of a certain class of bicoloured ribbon graphs with arbitrary genus.

We calculate the Kaluza-Klein spectrum of spin-2 fluctuations around the $\mathcal{N}=3$ warped ${\mathrm{AdS}}_4\times M_6$ solution in massive IIA supergravity. This solution was conjectured to be dual to the $D=3$ $\mathcal{N}=3$ superconformal $\mathrm{SU}(N)$ Chern-Simons matter theory with level $k$ and 2 adjoint chiral multiplets. The $\mathrm{SO}(3{)}_R\times \mathrm{SO}(3{)}_D$ isometry of the $\mathcal{N}=3$ solution is identified with the $\mathrm{SU}(2{)}_F\times \mathrm{SU}(2{)}_{\mathcal{R}}$ global symmetry of the dual $\mathcal{N}=3$ supersymmetric conformal field theory (SCFT). We show that the $\mathrm{SO}(3{)}_R\times \mathrm{SO}(3{)}_D$ quantum numbers and the AdS energies carried by the BPS spin-2 modes match precisely with those of the spin-2 gauge invariant operators in the short multiplets of operators in the $\mathcal{N}=3$ SCFT. We also compute the Euclidean action of the $\mathcal{N}=3$ solution and the free energy of the $\mathcal{N}=3$ SCFT on $S^3$, in the limit $N\gg k$. Remarkably, the results show a complete agreement.

Recently, it was realized that nonperturbative instanton effects can be generated to all orders by perturbation theory around a degenerate minima via the Dunne-Ünsal relation in several quantum mechanical systems. In this work we verify the Dunne-Ünsal relation for resonance energy levels of one-dimensional polynomial anharmonic oscillators. We show that the relation is applicable to cubic and quartic anharmonic oscillators which are genus-one potentials. However for higher order (higher genus) anharmonic potentials the relation is not satisfied and is subject to a certain extension.

The quasinormal modes of relativistic compact objects encode important information about the gravitational response associated with astrophysical phenomena. Detecting such oscillations would provide us with a unique understanding of the properties of compact stars and may give definitive evidence for the existence of black holes. However, computing quasinormal modes in realistic astrophysical environments is challenging due to the complexity of the spacetime background and of the dynamics of the perturbations. We discuss two complementary methods for computing the quasinormal modes of spherically symmetric astrophysical systems, namely, the direct integration method and the continued-fraction method. We extend these techniques to dealing with generic coupled systems of linear equations, with the only assumption being that the interaction between different fields is effectively localized within a finite region. In particular, we adapt the continued-fraction method to include cases where a series solution can be obtained only outside an effective region. As an application, we compute the polar quasinormal modes of boson stars by using the continued-fraction method for the first time. The methods discussed here can be applied to other situations in which the perturbations effectively couple only within a finite region of space.

We construct a class of stationary and axisymmetric solutions to the five-dimensional Einstein-Maxwell-dilaton gravity, which describe configurations of charged rotating black objects with Kaluza-Klein asymptotics. The solutions are constructed by uplifting a vacuum seed solution to six dimensions, performing a boost and a subsequent circle reduction. We investigate the physical properties of the charged solutions and obtain their general relations to the properties of the vacuum seed. We also derive the gyromagnetic ratio and the Smarr-like relations. As particular cases, we study three solutions, which describe a charged rotating black string, a charged rotating black ring on Kaluza-Klein bubbles, and a superposition of two black holes and a Kaluza-Klein bubble.

We study linearized equations of a ghost-free gravity in four- and higher-dimensional spacetimes. We consider versions of such a theory where the nonlocal modification of the $\square$ operator has the form $\square \exp [(-\square /{\mu }^2{)}^N]$, where $N=1$ or $N=2n$. We first obtain the Newtonian gravitational potential for a point mass for such models and demonstrate that it is finite and regular in any number of spatial dimensions $d\ge 3$. The second result of the paper is calculation of the gravitational field of an ultrarelativistic particle in such theories. And finally, we study a head-on collision of two ultrarelativistic particles. We formulated conditions of the apparent horizon formation and showed that there exists a mass gap for mini-black-hole production in the ghost-free theory of gravity. In the case when the center-of-mass energy is sufficient for the formation of the apparent horizon, the latter has two branches, the outer and the inner ones. When the energy increases the outer horizon tends to the Schwarzschild-Tangherlini limit, while the inner horizon becomes closer to $r=0$.

We present three-dimensional simulations of the dynamics of binary neutron star mergers from the late stage of the inspiral process up to $\sim 20\mathrm{ms}$ after the system has merged, either to form a hypermassive neutron star or a rotating black hole. We investigate five equal mass models of total gravitational mass 2.207, 2.373, 2.537, 2.697, and $2.854M_{\odot }$, respectively, and four unequal mass models with $M_{\mathrm{ADM}}\simeq 2.53M_{\odot }$ and $q\simeq 0.94$, 0.88, 0.83, and 0.77 (where $q=M^{(1)}/M^{(2)}$ is the mass ratio). We use a semirealistic equation of state, namely, the seven-segment piecewise polytropic SLyPP with a thermal component given by ${\mathrm{\Gamma }}_{\text{th}}=1.8$. We have also compared the resulting dynamics (for one model) using both the BSSN-NOK and CCZ4 methods for the evolution of the gravitational sector and also different reconstruction methods for the matter sector, namely, PPM, WENO, and MP5. Our results show agreement at high resolution, but superiority of BSSN-NOK supplemented by WENO reconstruction at lower resolutions. One of the important characteristics of the present investigation is that for the first time it has been done using only publicly available open source software: the Einstein Toolkit code, deployed for the dynamical evolution, and the LORENE code, for the generation of the initial models. All of the source code and parameters used for the simulations have been made publicly available. This not only makes it possible to rerun and reanalyze our data but also enables others to directly build upon this work for future research.

We discuss the potential of Athena x-ray telescope, in particular of its x-ray integral field unit (X-IFU), for detection of the signal from the light-weight decaying dark matter with mass in the keV range. We show that high energy resolution and large collection area of X-IFU will provide an improvement of sensitivity which will be sufficient for the full test of the neutrino minimal extension of the standard model ($\nu \mathrm{MSM}$). Search for the narrow spectral line produced by the decay of the dark matter sterile neutrino in the spectra of dwarf spheroidal galaxies with X-IFU will explore the whole allowed range masses and mixing angles of the $\nu \mathrm{MSM}$ lightest sterile neutrino and in this way either to find the dark matter signal or rule out the $\nu \mathrm{MSM}$ model.

We compute the dark matter velocity dispersion tensor up to third order in perturbation theory using the Lagrangian formalism, revealing growing solutions at the third and higher orders. Our results are general and can be used for any other perturbative formalism. As an application, corrections to the matter power spectrum are calculated, and we find that some of them have the same structure as those in the effective field theory of large-scale structure, with “EFT-like” coefficients that grow quadratically with the linear growth function and are further suppressed by powers of the logarithmic linear growth factor $f$; other corrections present additional $k$ dependence. Due to the velocity dispersions, there exists a free-streaming scale that suppresses the whole 1-loop power spectrum. Furthermore, we find that as a consequence of the nonlinear evolution, the free-streaming length is shifted towards larger scales, wiping out more structure than that expected in linear theory. Therefore, we argue that the formalism developed here is better suited for a perturbation treatment of warm dark matter or neutrino clustering, where the velocity dispersion effects are well known to be important. We discuss implications related to the nature of dark matter.

We study the detectability of circular polarization in a stochastic gravitational wave background from various sources such as supermassive black hole binaries, cosmic strings, and inflation in the early universe with pulsar timing arrays. We calculate generalized overlap reduction functions for the circularly polarized stochastic gravitational wave background. We find that the circular polarization cannot be detected for an isotropic background. However, there is a chance to observe the circular polarization for an anisotropic gravitational wave background. We also show how to separate polarized gravitational waves from unpolarized gravitational waves.

We study thermal transport in strongly disordered, strongly interacting quantum field theories without quasiparticles using gauge-gravity duality. We analyze linear perturbations of black holes with broken translational symmetry in Einstein-Maxwell-dilaton theories of gravity. Using general geometric arguments in the bulk, we derive bounds on thermal conductivity for the dual disordered field theories in one and two spatial dimensions. In the latter case, the thermal conductivity is always nonzero at finite temperature, so long as the dilaton potential is bounded from below. Hence, generic holographic models make nontrivial predictions about the thermal conductivity in a strongly disordered, strongly coupled metal in two spatial dimensions.

We complete the study of a class of string-motivated effective supergravity theories in which modulus-induced soft supersymmetry breaking is sufficiently suppressed in the observable sector so as to be competitive with anomaly-mediated supersymmetry breaking. Here we consider deflected “mirage mediation” (DMM), where contributions from gauge mediation are added to those arising from gravity mediation and anomaly mediation. We update previous work that surveyed the rich parameter space of such theories, in light of data from the CERN Large Hadron Collider (LHC) and recent dark matter detection experiments. Constraints arising from LHC superpartner searches at $\sqrt{s}=8\mathrm{TeV}$ are considered, and discovery prospects at $\sqrt{s}=14\mathrm{TeV}$ are evaluated. We find that deflected mirage mediation generally allows for $SU(3)$-charged superpartners of significantly lower mass (given current knowledge of the Higgs mass and neutralino relic density) than was found for the “pure” mirage mediation models of Kachru et al. [Phys. Rev. D 68, 046005 (2003)]. Consequently, discovery prospects are enhanced for many combinations of matter multiplet modular weights. We examine the experimental challenges that will arise due to the prospect of highly compressed spectra in DMM, and the correlation between accessibility at the LHC and discovery prospects at large-scale liquid xenon dark matter detectors.

We consider a simplified model for Majorana fermion dark matter and explore constraints from direct, indirect and LHC collider searches. The dark matter is assumed to couple to the Standard Model through a vector mediator with axial-vector interactions. We provide detailed analyses of LHC monojet searches and IceCube limits on dark matter annihilation in the Sun. In particular, we develop a method for calculating limits on simplified WIMP dark matter models from public IceCube data, which are only available for a limited number of Standard Model final states. We demonstrate that LHC and IceCube searches for Majorana dark matter are complementary and derive new limits on the dark matter and mediator masses, including in addition constraints from LHC dijet searches, direct detection and the dark matter relic density.

We conduct a model-independent effective theory analysis of hypercharged fields with various spin structures towards understanding the diboson excess found in LHC run I, as well as possible future anomalies involving $WZ$ and $WH$ modes. Within the assumption of no additional physics beyond the standard model up to the scale of the possible diboson resonance, we show that a hypercharged scalar and a spin 2 particle do not have tree-level $WZ$ and $WH$ decay channels up to dimension 5 operators, and cannot therefore account for the anomaly, whereas a hypercharged vector is a viable candidate provided we also introduce a $Z^{\prime }$ in order to satisfy electroweak precision constraints. We calculate bounds on the $Z^{\prime }$ mass consistent with the ATLAS/CMS diboson signals as well as electroweak precision data, taking into account both LHC run I and II data.