We apply Schrödinger-functional techniques to the SU(2) lattice gauge theory with $N_f=2$ flavors of fermions in the adjoint representation. Our use of hypercubic smearing enables us to work at stronger couplings than did previous studies, before encountering a critical point and a bulk phase boundary. Measurement of the running coupling constant gives evidence of an infrared fixed point $g_{*}$ where $1/g_{*}^2=0.20(4)(3)$. At the fixed point, we find a mass anomalous dimension ${\gamma }_m(g_{*})=0.31(6)$.

In this work we study the radiative decay of dynamically generated $J^P=\frac{1^{-}}{2}$ charm baryons into the ground state $J^P=\frac{1^{+}}{2}$ baryons. Since different theoretical interpretations of these baryonic resonances and, in particular, of the ${\Lambda }_c(2595)$, give different predictions, a precise experimental measurement of these decays would be an important step for understanding their nature.

The electromagnetic decay ${\Sigma }^0(1385)\to \Lambda \gamma$ was studied using the CLAS detector at the Thomas Jefferson National Accelerator Facility. A real photon beam with a maximum energy of 3.8 GeV was incident on a proton target, producing an exclusive final state of $K^{+}{\Sigma }^{*0}$. We report the decay widths ratio ${\Sigma }^0(1385)\to \Lambda \gamma /{\Sigma }^0(1385)\to \Lambda {\pi }^0=1.42\pm 0.12(\mathrm{stat}{)}_{-0.07}^{+0.11}(\mathrm{sys})\%$. This ratio is larger than most theoretical predictions by factors ranging from 1.5–3, but is consistent with the only other experimental measurement. From the reported ratio we calculate the partial width and electromagnetic transition magnetic moment for ${\Sigma }^0(1385)\to \Lambda \gamma$.

Finite-volume lattice QCD calculations offer the possibility of extracting resonance parameters from the energy-dependent elastic phase-shift computed using the Lüscher technique. In this letter, as a trial of the method, we report on the extraction of the nonresonant phase-shift for $S$ and $D$-wave $\pi \pi$ isospin-2 scattering from dynamical lattice QCD computations. We define a variational basis of operators resembling pairs of pions of definite relative momentum and extract a spectrum of excited states that maps to phase-shifts at a set of discrete scattering momenta. Computations are performed with pion masses between 400 and 520 MeV on multiple spatial volumes. We observe no significant quark mass dependence in the phase-shifts extracted which are in reasonable agreement with the available experimental data at low momentum.

Constraint analysis of the three-dimensional massive gravity, the so-called new massive gravity, is studied in the Palatini formalism. We show that amongst 6 components of the metric, 2 are dynamical, which is compatible with the existence of one vector massive graviton in the linearized theory (Fierz-Pauli theory).

We present results concerning the nonperturbative evaluation of the renormalization constant for the quark field, $Z_q$, from lattice simulations with twisted-mass quarks and three values of the lattice spacing. We use the regularization-invariant momentum-subtraction (RI’-MOM) scheme. $Z_q$ has very large lattice spacing artefacts; it is considered here as a test bed to elaborate accurate methods which will be used for other renormalization constants. We recall and develop the nonperturbative correction methods and propose tools to test the quality of the correction. These tests are also applied to the perturbative correction method. We check that the lattice-spacing artefacts indeed scale as $a^2{p}^2$. We then study the running of $Z_q$ with particular attention to the nonperturbative effects, presumably dominated by the dimension-two gluon condensate $⟨A^2⟩$ in Landau gauge. We show indeed that this effect is present, and not small. We check its scaling in physical units, confirming that it is a continuum effect. It gives a $\sim 4\%$ contribution at 2 GeV. Different variants are used in order to test the reliability of our result and estimate the systematic uncertainties. Finally, combining all our results and using the known Wilson coefficient of $⟨A^2⟩$, we find $g^2({\mu }^2)⟨A^2{⟩}_{{\mu }^2\mathrm{CM}}=2.01(11){(}_{-0.73}^{+0.61}){\mathrm{GeV}}^2$ at $\mu =10\mathrm{GeV}$, the local operator $A^2$ being renormalized in the $\overline{\mathrm{MS}}$ scheme. This last result is in fair agreement within uncertainties with the value independently extracted from the strong coupling constant. We convert the nonperturbative part of $Z_q$ from the regularization-invariant momentum-subtraction (RI’-MOM) scheme to $\overline{\mathrm{MS}}$. Our result for the quark field renormalization constant in the $\overline{\mathrm{MS}}$ scheme is $Z_q^{\overline{\mathrm{MS}}\mathrm{pert}}((2\mathrm{GeV}{)}^2,g_{\mathrm{bare}}^2)=0.750(3)(7)-0.313(20)(g_{\mathrm{bare}}^2-1.5)$ for the perturbative contribution and $Z_q^{\overline{\mathrm{MS}}\mathrm{nonperturbative}}((2\mathrm{GeV}{)}^2,g_{\mathrm{bare}}^2)=0.781(6)(21)-0.313(20)(g_{\mathrm{bare}}^2-1.5)$ when the nonperturbative contribution is included.

We construct different neutral blackfold solutions in Anti-de Sitter and de Sitter background spacetimes in the limit where the cosmological constant is taken to be much smaller than the horizon size. This includes a class of blackfolds with horizons that are products of odd-spheres times a transverse sphere, for which the thermodynamic stability is also studied. Moreover, we exhibit a specific case in which the same blackfold solution can describe different limiting black hole spacetimes therefore illustrating the geometric character of the blackfold approach. Furthermore, we show that the higher-dimensional Kerr-(Anti)-de Sitter black hole allows for ultraspinning regimes in the same limit under consideration and demonstrate that this is correctly described by a pancaked blackfold geometry. We also give evidence for the possibility of saturating the rigidity theorem in these backgrounds.

We investigate whether there is any cosmological evidence for a scalar field with a mass and coupling to matter which change accordingly to the properties of the astrophysical system it “lives in,” without directly focusing on the underlying mechanism that drives the scalar field scale-dependent-properties. We assume a Yukawa type of coupling between the field and matter and also that the scalar-field mass grows with density, in order to overcome all gravity constraints within the Solar System. We analyze three different gravitational systems assumed as “cosmological indicators”: supernovae type Ia, low surface brightness spiral galaxies and clusters of galaxies. Results show (i) a quite good fit to the rotation curves of low surface brightness galaxies only using visible stellar and gas-mass components is obtained; (ii) a scalar field can fairly well reproduce the matter profile in clusters of galaxies, estimated by x-ray observations and without the need of any additional dark matter; and (iii) there is an intrinsic difficulty in extracting information about the possibility of a scale-dependent massive scalar field (or more generally about a varying gravitational constant) from supernovae type Ia.

Using a solution generating technique based on the symmetries of the dimensionally reduced Lagrangian we derive an exact solution of the Einstein-Maxwell-Dilaton field equations in five dimensions describing a system of two general nonextremally charged static Kaluza-Klein black holes with spherical horizons. We investigate some of its thermodynamic properties and we also show how to recover various known solutions, in particular, cases.

In the Randall-Sundrum II braneworld model, it has been conjectured, according to the AdS/CFT correspondence, that a brane-localized black hole (BH) larger than the bulk AdS curvature scale $\ell$ cannot be static, and it is dual to a four-dimensional BH emitting Hawking radiation through some quantum fields. In this scenario, the number of the quantum field species is so large that this radiation changes the orbital evolution of a BH binary. We derived the correction to the gravitational waveform phase due to this effect and estimated the upper bounds on $\ell$ by performing Fisher analyses. We found that the Deci-Hertz Interferometer Gravitational Wave Observatory and the Big Bang Observatory (DECIGO/BBO) can give a stronger constraint than the current tabletop result by detecting gravitational waves from small mass BH/BH and BH/neutron star (NS) binaries. Furthermore, DECIGO/BBO is expected to detect ${10}^5$ BH/NS binaries per year. Taking this advantage, we find that DECIGO/BBO can actually measure $\ell$ down to $\ell =0.33\mu \mathrm{m}$ for a 5 yr observation if we know that binaries are circular a priori. This is about 40 times smaller than the upper bound obtained from the tabletop experiment. On the other hand, when we take eccentricities into binary parameters, the detection limit weakens to $\ell =1.5\mu \mathrm{m}$ due to strong degeneracies between $\ell$ and eccentricities. We also derived the upper bound on $\ell$ from the expected detection number of extreme mass ratio inspirals with LISA and BH/NS binaries with DECIGO/BBO, extending the discussion made recently by McWilliams [Phys. Rev. Lett. 104, 141601 (2010)]. We found that these less robust constraints are weaker than the ones from phase differences.

In this paper we consider a massless scalar field, with a possible coupling $\xi$ to the Ricci scalar in a $D$ dimensional Friedmann-Lemaître-Robertson-Walker space-time with a constant deceleration parameter $q=ϵ-1$, $ϵ=-\dot{H}/H^2$. Correlation functions for the Bunch-Davies vacuum of such a theory have long been known to be infrared divergent for a wide range of values of $ϵ$. We resolve these divergences by explicitly matching the space-time under consideration to a space-time without infrared divergencies. Such a procedure ensures that all correlation functions with respect to the vacuum in the space-time of interest are infrared finite. In this newly defined vacuum we construct the coincidence limit of the propagator and as an example calculate the expectation value of the stress-energy tensor. We find that this approach gives both in the ultraviolet and in the infrared satisfactory results. Moreover, we find that, unless the effective mass due to the coupling to the Ricci scalar $\xi R$ is negative, quantum contributions to the energy density always dilute away faster, or just as fast, as the background energy density. Therefore, quantum backreaction is insignificant at the one-loop order, unless $\xi R$ is negative. Finally we compare this approach with known results where the infrared is regulated by placing the Universe in a finite box. In an accelerating universe, the results are qualitatively the same, provided one identifies the size of the Universe with the physical Hubble radius at the time of the matching. In a decelerating universe, however, the two schemes give different late time behavior for the quantum stress-energy tensor. This happens because in this case the length scale at which one regulates the infrared becomes sub-Hubble at late times.

Numerical simulations of the accretion of test scalar fields with nonstandard kinetic terms (of the $k$-essence type) onto a Schwarzschild black hole are performed. We find a full dynamical solution for the spherical accretion of a Dirac-Born-Infeld type scalar field. The simulations show that the accretion eventually settles down to a well-known stationary solution. This particular analytical steady state solution maintains two separate horizons. The standard horizon is for the usual particles propagating with the limiting speed of light, while the other sonic horizon is for the $k$-essence perturbations propagating with the speed of sound around this accreting background. For the case where the $k$-essence perturbations propagate superluminally, we show that one can send signals from within a black hole during the approach to the stationary solution. We also find that a ghost condensate model settles down to a stationary solution during the accretion process.

We propose a simple scenario which explains the observed matter-antimatter imbalance and the origin of dark matter in the Universe. We use the Einstein-Cartan-Sciama-Kibble theory of gravity which naturally extends general relativity to include the intrinsic spin of matter. Spacetime torsion produced by spin generates, in the classical Dirac equation, the Hehl-Datta term which is cubic in spinor fields. We show that under a charge-conjugation transformation this term changes sign relative to the mass term. A classical Dirac spinor and its charge conjugate therefore satisfy different field equations. Fermions in the presence of torsion have higher energy levels than antifermions, which leads to their decay asymmetry. Such a difference is significant only at extremely high densities that existed in the very early Universe. We propose that this difference caused a mechanism, according to which heavy fermions existing in such a Universe and carrying the baryon number decayed mostly to normal matter, whereas their antiparticles decayed mostly to hidden antimatter which forms dark matter. The conserved total baryon number of the Universe remained zero.

In a recent reformulation of three-dimensional new massive gravity, the field equations of the theory consist of a massive (tensorial) Klein-Gordon type equation with a curvature-squared source term and a constraint equation. Using this framework, we present all algebraic type $D$ solutions of new massive gravity with constant and nonconstant scalar curvatures. For constant scalar curvature, they include homogeneous anisotropic solutions which encompass both solutions originating from topologically massive gravity, Bianchi types $II$, $VIII$, $IX$, and those of non-topologically massive gravity origin, Bianchi types $V{I}_0$ and $VI{I}_0$. For a special relation between the cosmological and mass parameters, $\lambda =m^2$, they also include conformally flat solutions, and, in particular, those being locally isometric to the previously-known Kaluza-Klein type ${\mathrm{AdS}}_2\times S^1$ or ${\mathrm{dS}}_2\times S^1$ solutions. For nonconstant scalar curvature, all the solutions are conformally flat and exist only for $\lambda =m^2$. We find two general metrics which possess at least one Killing vector and comprise all such solutions. We also discuss some properties of these solutions, delineating among them black hole type solutions.

We study the thermodynamics and the thermodynamic geometries of charged rotating Bañados-Teitelboim-Zanelli black holes in ($2+1$)-gravity. We investigate the thermodynamics of these systems within the context of the Weinhold and Ruppeiner thermodynamic geometries and the recently developed formalism of geometrothermodynamics. Considering the behavior of the heat capacity and the Hawking temperature, we show that Weinhold and Ruppeiner geometries cannot describe completely the thermodynamics of these black holes and of their limiting case of vanishing electric charge. In contrast, the Legendre invariance imposed on the metric in geometrothermodynamics allows one to describe the charged rotating Bañados-Teitelboim-Zanelli black holes and their limiting cases in a consistent and invariant manner.

The standard nonlinear perturbation theory of the gravitational instability is extended to incorporate the nonlocal bias, redshift-space distortions, and primordial non-Gaussianity. We show that local Eulerian bias is not generally compatible with local Lagrangian bias in the nonlinear regime. The Eulerian and Lagrangian biases are nonlocally related order by order in the general perturbation theory. The relation between Eulerian and Lagrangian kernels of density perturbations with biasing is derived. The effects of primordial non-Gaussianity and redshift-space distortions are also incorporated in our general formalism, and diagrammatic methods are introduced. Vertex resummations of higher-order perturbations in the presence of bias are considered. Resummations of Lagrangian bias are shown to be essential to handle biasing schemes in a general framework.

Recently, an analysis of data from the Fermi Gamma Ray Space Telescope has revealed a flux of gamma rays concentrated around the inner 0.5 degrees of the Milky Way, with a sharply peaked spectrum at 2—4 GeV. Interpreted as the products of annihilating dark matter, this implies a dark matter particle with mass between 7.3 and 9.2 GeV annihilating primarily to charged leptons. This is comparable to the mass range required to fit signals reported by CoGeNT and DAMA/LIBRA. In addition to gamma rays, dark matter is predicted to produce energetic electrons and positrons which emit synchrotron while propagating through the galactic magnetic field. In this letter, we calculate the flux and spectrum of this synchrotron emission and compare the results to measurements from the WMAP satellite. We find that a sizable flux of hard synchrotron emission is predicted in this scenario, and that this can easily account for the observed intensity, spectrum, and morphology of the "WMAP haze.”

In this paper we construct a phenomenological model in which the time variation of the fine-structure constant, $\alpha$, is induced by a parity and charge-parity (PCP) violating interaction. Such a PCP violation in the photon sector has a distinct physical origin from that in the conventional models of this kind. We calculate the cosmological birefringence so induced in our model and show that it in turn produces a new nonvanishing multipole moment correlation between the temperature and the polarization anisotropies in the CMB spectrum. We have also calculated the amount of optical rotation due to a strong background magnetic field and the effect of our new PCP violating term on the variation of $\alpha$ during the cosmic evolution. We found that only in the radiation dominated era can the contribution of the new PCP violating term to the variation of $\alpha$ be nonvanishing.

The XENON100 experiment, located at the Laboratori Nazionali del Gran Sasso, aims to directly detect dark matter in the form of weakly interacting massive particles via their elastic scattering off xenon nuclei. We present a comprehensive study of the predicted electronic recoil background coming from radioactive decays inside the detector and shield materials and intrinsic radioactivity in the liquid xenon. Based on GEANT4 Monte Carlo simulations using a detailed geometry together with the measured radioactivity of all detector components, we predict an electronic recoil background in the energy region of interest and 30 kg fiducial mass of less than ${10}^{-2}\mathrm{events}·{\mathrm{kg}}^{-1}·{\mathrm{day}}^{-1}·\mathrm{ke}{\mathrm{V}}^{-1}$, consistent with the experiment’s design goal. The predicted background spectrum is in very good agreement with the data taken during the commissioning of the detector in Fall 2009.