The equations of motion of multiple M0-brane (multiple M-wave or mM0) systems in an arbitrary $D=11$ supergravity superspace, which generalize the matrix model equations for the case of interaction with a generic 11-dimensional supergravity background, are obtained in the frame of the superembedding approach. We also derive the Bogomol’nyi-Prasad-Sommerfeld (BPS) equations for supersymmetric bosonic solutions of these mM0 equations and show that the set of $1/2$ BPS solutions contain a fuzzy sphere modeling M2 brane as well as that the Nahm equation appears as a particular case of the $1/4$ BPS equations.

In the context of the $1/N$ expansion, the validity of the Slavnov-Taylor identity relating three- and two-point functions for the $2+1$-dimensional noncommutative $C{P}^{N-1}$ model is investigated, up to subleading $1/N$ order, in the Landau gauge.

We show that the $\mu$ problem and the strong $CP$ problem can be resolved in the context of the gauged $U(1{)}_R$ symmetry, realizing an automatic Peccei-Quinn symmetry. In this scheme, right-handed neutrinos can be introduced to explain small Majorana or Dirac neutrino mass. The $U(1{)}_R$ D-term mediated supersymmetry (SUSY) breaking, called the $U(1{)}_R$ mediation, gives rise to a specific form of the flavor-conserving superpartner masses. For the given solution to the $\mu$ problem, electroweak symmetry breaking condition requires the superpartners of the standard model at low energy to be much heavier than the gravitino. Thus, the dark matter candidate can be either gravitino or right-handed sneutrino. In the Majorana neutrino case, only gravitino is a natural dark matter candidate. On the other hand, in the Dirac neutrino case, the right-handed sneutrino can be also a dark matter candidate as it gets mass only from SUSY breaking. We discuss the non-thermal production of our dark matter candidates from the late decay of stau and find that the constraints from the big bang nucleosynthesis can be evaded for a TeV-scale stau mass.

We develop a scheme for the minimal coupling of all standard types of tensor and spinor field matter to Plebanski gravity. This theory is a geometric reformulation of vacuum general relativity in terms of two-form frames and connection one-forms, and provides a covariant basis for various quantization approaches. Using the spinor formalism we prove the consistency of the newly proposed matter coupling by demonstrating the full equivalence of Plebanski gravity plus matter to Einstein-Cartan gravity. As a by-product we also show the consistency of some previous suggestions for matter actions.

We present a high-order accurate discontinuous Galerkin method for evolving the spherically reduced Baumgarte-Shapiro-Shibata-Nakamura (BSSN) system expressed in terms of second-order spatial operators. Our multidomain method achieves global spectral accuracy and longtime stability on short computational domains. We discuss in detail both our scheme for the BSSN system and its implementation. After a theoretical and computational verification of the proposed scheme, we conclude with a brief discussion of issues likely to arise when one considers the full BSSN system.

We consider boson shells in scalar electrodynamics coupled to Einstein gravity. The interior of the shells can be empty space, or harbor a black hole or a naked singularity. We analyze the properties of these types of solutions and determine their domains of existence. We investigate the energy conditions and present mass formulae for the composite black hole–boson shell systems. We demonstrate that these types of solutions violate black hole uniqueness.

We investigate here the particle acceleration by naked singularities to arbitrarily high center of mass energies. Recently it has been suggested that black holes could be used as particle accelerators to probe the Planck scale physics. We show that the naked singularities serve the same purpose and probably would do better than their black hole counterparts. We focus on the scenario of a self-similar gravitational collapse starting from a regular initial data, leading to the formation of a globally naked singularity. It is seen that when particles moving along timelike geodesics interact and collide near the Cauchy horizon, the energy of collision in the center of mass frame will be arbitrarily high, thus offering a window to Planck scale physics.

Cosmological parameter uncertainties are often stated assuming a particular model, neglecting the model uncertainty, even when Bayesian model selection is unable to identify a conclusive best model. Bayesian model averaging is a method for assessing parameter uncertainties in situations where there is also uncertainty in the underlying model. We apply model averaging to the estimation of the parameters associated with the primordial power spectra of curvature and tensor perturbations. We use CosmoNest and MultiNest to compute the model evidences and posteriors, using cosmic microwave data from WMAP, ACBAR, BOOMERanG, and CBI, plus large-scale structure data from the SDSS DR7. We find that the model-averaged 95% credible interval for the spectral index using all of the data is $0.940<n_{\mathrm{s}}<1.000$, where $n_{\mathrm{s}}$ is specified at a pivot scale $0.015{\mathrm{Mpc}}^{-1}$. For the tensors model averaging can tighten the credible upper limit, depending on prior assumptions.

There has been considerable interest in recent years in cosmological models in which we inhabit a very large, underdense void as an alternative to dark energy. A long-standing objection to this proposal is that observations limit our position to be very close to the void center. By selecting from a family of void profiles that fit supernova luminosity data, we carefully determine how far from the center we could be. To do so, we use the observed dipole component of the cosmic microwave background, as well as an additional stochastic peculiar velocity arising from primordial perturbations. We find that we are constrained to live within 80 Mpc of the center of a void—a somewhat weaker constraint than found in previous studies, but nevertheless a strong violation of the Copernican principle. By considering how such a Gpc-scale void would appear on the microwave sky, we also show that there can be a maximum of one of these voids within our Hubble radius. Hence, the constraint on our position corresponds to a fraction of the Hubble volume of order ${10}^{-8}$. Finally, we use the fact that void models only look temporarily similar to a cosmological-constant-dominated universe to argue that these models are not free of temporal fine-tuning.

This article continues the study of the category of harmonious field models that was recently introduced as a kinetically nonlinear generalization of the well-known harmonic category of multiscalar fields over a supporting brane world sheet in a target space with a curved Riemannian metric. Like the perfectly harmonious case of which a familiar example is provided by ordinary barotropic perfect fluids, another important subcategory is the simply harmonious case, for which it is shown that as well as “wiggle” modes of the underlying brane world sheet, and sound type longitudinal modes, there will also be transverse shake modes that propagate at the speed of light. Models of this type are shown to arise from a non-Abelian generalization of the Witten mechanism for conducting string formation by ordinary scalar fields with a suitable quartic self-coupling term in the action.

In this paper we examine the cosmological consequences of fourth order Galileon gravity. We carry out detailed investigations of the underlying dynamics and demonstrate the stability of one de Sitter phase. The stable de Sitter phase contains a Galileon field $\pi$ which is an increasing function of time ($\dot{\pi }>0$). Using the required suppression of the fifth force, supernovae, Baryon acoustic oscillations, and CMB data, we constrain parameters of the model. We find that the $\pi$ matter coupling parameter $\beta$ is constrained to small numerical values such that $\beta <0.02$. We also show that the parameters of the third and fourth order in the action $(c_3,c_4)$ are not independent and with reasonable assumptions, we obtain constraints on them. We investigate the growth history of the model and find that the subhorizon approximation is not allowed for this model. We demonstrate strong scale dependence of linear perturbations in the fourth order Galileon gravity.

We generalize the cosmic energy equation to the case when massive particles interact via a modified gravitational potential of the form $\varphi (a,r)$, which is allowed to explicitly depend upon the cosmological time through the expansion factor $a(t)$. Using the nonrelativistic approximation for particle dynamics, we derive the equation for the cosmological expansion which has the form of the Friedmann equation with a renormalized gravitational constant. The generalized Layzer–Irvine cosmic energy equation and the associated cosmic virial theorem are applied to some recently proposed modifications of the Newtonian gravitational interaction between dark-matter particles. We also draw attention to the possibility that the cosmic energy equation may be used to probe the expansion history of the universe thereby throwing light on the nature of dark matter and dark energy.

The goal of this paper is twofold: to explore the response of classical charges to electromagnetic force at the level of unity in natural units and to establish a criterion that determines physical parameters for which the related radiation-reaction effects are detectable. In pursuit of this goal, the Landau-Lifshitz equation is solved analytically for an arbitrary (transverse) electromagnetic pulse. A comparative study of the radiation emission of an electron in a linearly polarized pulse for the Landau-Lifshitz equation and for the Lorentz force equation reveals the radiation-reaction-dominated regime, in which radiation-reaction effects overcome the influence of the external fields. The case of a relativistic electron that is slowed down by a counterpropagating electromagnetic wave is studied in detail. We further show that when the electron experiences acceleration of order unity, the dynamics of the Lorentz force equation, the Landau-Lifshitz equation and the Lorentz-Abraham-Dirac equation all result in different radiation emission that could be distinguished in experiment. Finally, our analytic and numerical results are compared with those appearing in the literature.

We present a qualitatively new approach to discover Higgs bosons of the minimal supersymmetric standard model (MSSM) at the LHC using jet substructure techniques applied to boosted Higgs decays. These techniques are ideally suited to the MSSM, since the lightest Higgs boson overwhelmingly decays to $b\overline{b}$ throughout the entire parameter space, while the heavier neutral Higgs bosons, if light enough to be produced in a cascade, also predominantly decay to $b\overline{b}$. The Higgs production we consider arises from superpartner production where superpartners cascade decay into Higgs bosons. We study this mode of Higgs production for several superpartner hierarchies: $m_{\tilde{q}}$, $m_{\tilde{g}}>m_{\tilde{W},\tilde{B}}>m_h+\mu$; $m_{\tilde{q}}$, $m_{\tilde{g}}>m_{\tilde{W},\tilde{B}}>m_{h,H,A}+\mu$; and $m_{\tilde{q}}$, $m_{\tilde{g}}>m_{\tilde{W}}>m_h+\mu$ with $m_{\tilde{B}}\simeq \mu$. In these cascades, the Higgs bosons are boosted, with $p_T>200\mathrm{GeV}$ a large fraction of the time. Since Higgses appear in cascades originating from squarks and/or gluinos, the cross section for events with at least one Higgs can be the same order as squark/gluino production. Given $10{\mathrm{fb}}^{-1}$ of 14 TeV LHC data, with $m_{\tilde{q}}\lesssim 1\mathrm{TeV}$, and one of the above superpartner mass hierarchies, our estimate of $S/\sqrt{B}$ of the Higgs signal is sufficiently high that the $b\overline{b}$ mode can become the discovery mode of the lightest Higgs boson of the MSSM.

We address the issue why the number and the location of magnetic monopoles detected on lattice configurations are gauge dependent, in contrast with the physical expectation that monopoles have a gauge-invariant status. By use of the non-Abelian Bianchi identities we show that monopoles are gauge-invariant, but the efficiency of the technique usually adopted to detect them depends on the choice of the gauge in a well understood way. In particular we have studied a class of gauges which interpolate between the Maximal Abelian gauge, where all monopoles are observed, and the Landau gauge, where all monopoles escape detection.

Results computed in lattice $\mathrm{QCD}+\mathrm{QED}$ are presented for the electromagnetic mass splittings of the low-lying hadrons. These are used to determine the renormalized, nondegenerate, light quark masses. It is found that $m_u^{\overline{\mathrm{MS}}}=2.24(10)(34)$, $m_d^{\overline{\mathrm{MS}}}=4.65(15)(32)$, and $m_s^{\overline{\mathrm{MS}}}=97.6(2.9)(5.5)\mathrm{MeV}$ at the renormalization scale 2 GeV, where the first error is statistical and the second systematic. We find the lowest-order electromagnetic splitting $(m_{{\pi }^{+}}-m_{{\pi }^0}{)}_{\mathrm{QED}}=3.38(23)\mathrm{MeV}$, the splittings including next-to-leading order, $(m_{{\pi }^{+}}-m_{{\pi }^0}{)}_{\mathrm{QED}}=4.50(23)\mathrm{MeV}$, $(m_{K^{+}}-m_{K^0}{)}_{\mathrm{QED}}=1.87(10)\mathrm{MeV}$, and the $m_u\ne m_d$ contribution to the kaon mass difference, $(m_{K^{+}}-m_{K^0}{)}_{(m_u-m_d)}=-5.840(96)\mathrm{MeV}$. All errors are statistical only, and the next-to-leading-order pion splitting is only approximate in that it does not contain all next-to-leading-order contributions. We also computed the proton-neutron mass difference, including for the first time, QED interactions in a realistic $2+1$ flavor calculation. We find $(m_p-m_n{)}_{\mathrm{QED}}=0.383(68)\mathrm{MeV}$, $(m_p-m_n{)}_{(m_u-m_d)}=-2.51(14)\mathrm{MeV}$ (statistical errors only), and the total $m_p-m_n=-2.13(16)(70)\mathrm{MeV}$, where the first error is statistical, and the second, part of the systematic error. The calculations are carried out on QCD ensembles generated by the RBC and UKQCD collaborations, using domain wall fermions and the Iwasaki gauge action (gauge coupling $\beta =2.13$ and lattice cutoff $a^{-1}\approx 1.78\mathrm{GeV}$). We use two lattice sizes, ${16}^3$ and ${24}^3$ ($(1.8\mathrm{fm}{)}^3$ and $(2.7\mathrm{fm}{)}^3$), to address finite-volume effects. Noncompact QED is treated in the quenched approximation. The valence pseudoscalar meson masses in our study cover a range of about 250 to 700 MeV, though we use only those up to about 400 MeV to quote final results. We present new results for the electromagnetic low-energy constants in SU(3) and SU(2) partially quenched chiral perturbation theory to the next-to-leading order, obtained from fits to our data. Detailed analysis of systematic errors in our results and methods for improving them are discussed. Finally, new analytic results for $\mathrm{SU}(2{)}_{\mathrm{L}}\times \mathrm{SU}(2{)}_{\mathrm{R}}$-plus-kaon chiral perturbation theory, including the one-loop logs proportional to ${\alpha }_{\mathrm{em}}m$, are given.

We investigate whether the lightest scalar mesons $\sigma$ and $\kappa$ have a large tetraquark component $\overline{q}\overline{q}qq$, as is strongly supported by many phenomenological studies. A search for possible light tetraquark states with $J^{\mathrm{PC}}=0^{++}$ and $I=0,2,1/2,3/2$ on the lattice is presented. We perform the two-flavor dynamical simulation with chirally improved quarks and the quenched simulation with overlap quarks, finding qualitative agreement between both results. The spectrum is determined using the generalized eigenvalue method with a number of tetraquark interpolators at the source and the sink, and we omit the disconnected contractions. The time dependence of the eigenvalues at the finite temporal extent of the lattice is explored also analytically. In all the channels, we unavoidably find the lowest scattering states $\pi (k)\pi (-k)$ or $K(k)\pi (-k)$ with back-to-back momentum $k=0,2\pi /L,\dots$. However, we find an additional light state in the $I=0$ and $I=1/2$ channels, which may be interpreted as the observed resonances $\sigma$ and $\kappa$ with a sizable tetraquark component. In the exotic repulsive channels $I=2$ and $I=3/2$, where no resonance is observed, we find no light state in addition to the scattering states.

A new approach to jet-shape identification based on linear regression is discussed. It is designed for searches for new particles at the TeV scale decaying hadronically with strongly collimated jets. We illustrate the method using a Monte Carlo simulation for $pp$ collisions at the LHC with the goal to reduce the contribution of QCD-induced events. We focus on a rather generic example $X\to t\overline{t}\to \mathrm{\text{hadrons}}$, with $X$ being a heavy particle, but the approach is well suited for reconstruction of other decay channels characterized by a cascade decay of known states.

We analyze the recent results of the MiniBooNE short-baseline experiment on ${\overline{\nu }}_{\mu }\to {\overline{\nu }}_e$ oscillations in a minimal model-independent framework of antineutrino mixing in conjunction with the positive Liquid Scintillating Neutrino Detector (LSND) signal and the negative KArlsruhe Rutherford Medium Energy Neutrino Experiment (KARMEN) measurements. We show that the data of the three short-baseline ${\overline{\nu }}_{\mu }\to {\overline{\nu }}_e$ experiments are compatible. Taking into account also the model-independent constraints due to the limits on short-baseline ${\overline{\nu }}_e$ disappearance obtained in reactor antineutrino experiments, we find that the favored region of the effective oscillation parameters lies within $2\times {10}^{-3}\lesssim {sin}^{2}2\vartheta \lesssim 5\times {10}^{-2}$ and $0.2\lesssim \Delta m^2\lesssim 2{\mathrm{eV}}^2$.