We investigate cosmological scenarios with a nonminimal derivative coupling between the scalar field and the curvature, examining both the quintessence and the phantom cases in zero and constant potentials. In general, we find that the universe transits from one de Sitter solution to another, determined by the coupling parameter. Furthermore, according to the parameter choices and without the need for matter, we can obtain a big bang, an expanding universe with no beginning, a cosmological turnaround, an eternally contracting universe, a big crunch, a big rip avoidance, and a cosmological bounce. This variety of behaviors reveals the capabilities of the present scenario.

We perform a sensitivity study of dark energy (DE) constraints from galaxy cluster surveys to uncertainties in the halo mass function, bias, and the mass-observable relation. For a set of idealized surveys, we evaluate cosmological constraints as priors on 16 nuisance parameters in the halo modeling are varied. We find that surveys with a higher mass limit are more sensitive to mass-observable uncertainties while surveys with low mass limits that probe more of the mass-function shape and evolution are more sensitive to mass-function errors. We examine the correlations among nuisance and cosmological parameters. Mass-function parameters are strongly positively (negatively) correlated with ${\Omega }_{\mathrm{DE}}$ ($w$). For the mass-observable parameters, ${\Omega }_{\mathrm{DE}}$ is most sensitive to the normalization and its redshift evolution while $w$ is more sensitive to redshift evolution in the variance. While survey performance is limited mainly by mass-observable uncertainties, the current level of mass-function error is responsible for up to a factor of 2 degradation in ideal cosmological constraints. For surveys that probe to low masses (${10}^{13.5}{h}^{-1}{M}_{\odot }$), even percent-level constraints on model nuisance parameters result in a degradation of $\sim \sqrt{2}$ (2) on ${\Omega }_{\mathrm{DE}}$ ($w$) relative to perfect knowledge.

We introduce a new form of coupling between dark energy and dark matter that is quadratic in their energy densities. Then we investigate the background dynamics when dark energy is in the form of exponential quintessence. The three types of quadratic coupling all admit late-time accelerating critical points, but these are not scaling solutions. We also show that two types of coupling allow for a suitable matter era at early times and acceleration at late times, while the third type of coupling does not admit a suitable matter era.

We report for the first time general geometrical expressions for the angular resolution of an arbitrary network of interferometric gravitational-wave (GW) detectors when the arrival time of a GW is unknown. We show explicitly elements that decide the angular resolution of a GW detector network. In particular, we show the dependence of the angular resolution on areas formed by projections of pairs of detectors and how they are weighted by sensitivities of individual detectors. Numerical simulations are used to demonstrate the capabilities of the current GW detector network. We confirm that the angular resolution is poor along the plane formed by current LIGO-Virgo detectors. A factor of a few to more than ten fold improvement of the angular resolution can be achieved if the proposed new GW detectors LCGT or AIGO are added to the network. We also discuss the implications of our results for the design of a GW detector network, optimal localization methods for a given network, and electromagnetic follow-up observations.

We present results on the mass and spin of the final black hole from mergers of equal mass, spinning black holes. The study extends over a broad range of initial orbital configurations, from direct plunges to quasicircular inspirals to more energetic orbits (generalizations of Newtonian elliptical orbits). It provides a comprehensive search of those configurations that maximize the final spin of the remnant black hole. We estimate that the final spin can reach a maximum spin $a/M_h\approx 0.99\pm 0.01$ for extremal black hole mergers. In addition, we find that, as one increases the orbital angular momentum from small values, the mergers produce black holes with mass and spin parameters $\{Mh/M,a/Mh\}$ spiraling around the values $\{{\widehat{M}}_h/M,\widehat{a}/M_h\}$ of a golden black hole. Specifically, $(M_h-{\widehat{M}}_h)/M\propto e^{\pm B\varphi }\cos \varphi$ and $(a-\widehat{a})/M_h\propto e^{\pm C\varphi }\sin \varphi$, with $\varphi$ a monotonically growing function of the initial orbital angular momentum. We find that the values of the parameters for the golden black hole are those of the final black hole obtained from the merger of a binary with the corresponding spinning black holes in a quasicircular inspiral.

If the equation of state of dark energy is anisotropic there will be additional quadrupole anisotropy in the cosmic microwave background induced by the time-dependent anisotropic stress quantified in terms of $\Delta w$. Assuming that the entire amplitude of the observed quadrupole is due to this anisotropy, we conservatively impose a limit of $|\Delta w|<2.1\times {10}^{-4}$ for any value of $w\ge -1$ assuming that ${\Omega }_{\mathrm{m}}<0.5$. This is considerably tighter than that which comes from supernovae. Stronger limits, up to a factor of 10, are possible for specific values of ${\Omega }_{\mathrm{m}}$ and $w$. Since we assume this component is uncorrelated with the stochastic component from inflation, we find that both the expectation value and the sample variance are increased. There is no improvement in the likelihood of an anomalously low quadrupole as suggested by previous work on an elliptical universe.

At nonzero temperature in QCD, about the deconfining phase transition there is a semiquark gluon plasma (semi-QGP), where the expectation value of the (renormalized) Polyakov loop is less than one. This can be modeled by a semiclassical expansion about a constant field for the vector potential, $A_0$, which is diagonal in color. We compute the shear viscosity in the semi-QGP by using the Boltzmann equation in the presence of this background field. To leading, logarithmic order in weak coupling, the dominant diagrams are given by the usual scattering processes of $2\to 2$ particles. For simplicity we also assume that both the number of colors and flavors are large. Near the critical temperature $T_c$, where the expectation value of the Polyakov loop is small, the overall density of colored fields decreases according to their color representation, with the density of quarks vanishes linearly with the loop, and that of gluons, quadratically. This decrease in the overall density dominates changes in the transport cross section. As a result, relative to that in the perturbative QGP, near $T_c$ the shear viscosity in the semi-QGP is suppressed by two powers of the Polyakov loop. In a semiclassical expansion, the suppression of colored fields depends only upon which color representation they lie in, and not upon their mass. That light and heavy quarks are suppressed in a common manner may help to explain the behavior of charm quarks at RHIC.

Little Higgs models with $T$ parity can easily satisfy electroweak precision tests and at the same time give a stable particle which is a candidate for cold dark matter. In addition to little Higgs heavy gauge bosons, this type of model predicts a set of new $T$-odd fermions, which may show quite interesting signatures at colliders. We study purely leptonic signatures of $T$-odd leptons at the (LHC.

Secluded dark matter models, in which weakly interacting massive particles annihilate first into metastable mediators, can present novel indirect detection signatures in the form of gamma rays and fluxes of charged particles arriving from directions correlated with the centers of large astrophysical bodies within the Solar System, such as the Sun and larger planets. This naturally occurs if the mean free path of the mediator is in excess of the solar (or planetary) radius. We show that existing constraints from water Cerenkov detectors already provide a novel probe of the parameter space of these models, complementary to other sources, with significant scope for future improvement from high angular resolution gamma-ray telescopes such as Fermi-LAT. Fluxes of charged particles produced in mediator decays are also capable of contributing a significant solar system component to the spectrum of energetic electrons and positrons, a possibility which can be tested with the directional and timing information of PAMELA and Fermi.

Recent BABAR limits on $\mathrm{BR}({\rm Y}(3S)\to \gamma a\to \gamma {\tau }^{+}{\tau }^{-})$ and $\mathrm{BR}({\rm Y}(3S)\to \gamma a\to \gamma {\mu }^{+}{\mu }^{-})$ provide increased constraints on the $ab\overline{b}$ coupling of a $CP$-odd Higgs boson, $a$, with $m_a<M_{{\rm Y}(3S)}$. We extract these limits from the BABAR data and compare to the limits previously obtained using other data sets, especially the CLEO-III $\mathrm{BR}({\rm Y}(1S)\to \gamma \to {\tau }^{+}{\tau }^{-})$ limits. Comparisons are made to predictions in the context of “ideal”-Higgs NMSSM scenarios, in which the lightest $CP$-even Higgs boson, $h_1$, can have mass below 105 GeV (as preferred by precision electroweak data) and yet can escape old LEP limits by virtue of decays to a pair of the lightest $CP$-odd Higgs bosons, $h_1\to a_1{a}_1$, with $m_{a_1}<2m_B$. Most such scenarios with $m_{a_1}<2m_{\tau }$ are eliminated, but the bulk of the $m_{a_1}>7.5\mathrm{GeV}$ scenarios, which are theoretically the most favored, survive. We also outline the impact of the new ALEPH LEP results in the $e^{+}{e}^{-}\to Z+4\tau$ channel. For $\tan \beta \ge 3$, only NMSSM ideal Higgs scenarios with $m_{h_1}\gtrsim 98\mathrm{GeV}$ and $m_{a_1}$ close to $2m_B$ satisfy the ALEPH limits. For $\tan \beta \lesssim 2$, the ALEPH limits are easily satisfied for the most theoretically preferred NMSSM scenarios, which are those with $m_{a_1}$ close to $2m_B$ and $m_{h_1}\sim 90–100\mathrm{GeV}$.

We show that in SU(2) Yang-Mills theories a simple relation exists between lattice gluon propagators in the Coulomb and Landau gauges and discuss the physical implications of such result. In particular, the realization of the Gribov-Zwanziger confinement mechanism in Coulomb gauge, linked to dual superconductivity, would imply that the standard BRST charge must be ill defined nonperturbatively. As a consequence, the Kugo-Ojima confinement criterion, which relies on BRST charge conservation beyond perturbation theory, would not be fulfilled.

Both in heavy-ion collisions and in magnetars very strong magnetic fields are produced, which has an influence on the phases of matter involved. In this paper we investigate the effect of strong magnetic fields ($B\sim 5m_{\pi }^2/e=1.7\times {10}^{19}\mathrm{G}$) on the chiral symmetry restoring phase transition using the Nambu–Jona-Lasinio model. It is observed that the pattern of phase transitions depends on the relative magnitude of the magnetic field and the instanton interaction strength. We study two specific regimes in the phase diagram, high chemical potential and zero temperature and vice versa, which are of relevance for neutron stars and heavy-ion collisions, respectively. In order to shed light on the behavior of the phase transitions, we study the dependence of the minima of the effective potential on the occupation of Landau levels. We observe a near degeneracy of multiple minima with differing occupation numbers, of which some become the global minimum upon changing the magnetic field or the chemical potential. These minima differ considerably in the amount of chiral symmetry breaking and, in some cases, also of isospin breaking.

The energy dependence of the neutrino-iron and antineutrino-iron inclusive charged-current cross sections and their ratio have been measured using a high-statistics sample with the MINOS near detector exposed to the NuMI beam from the main injector at Fermilab. Neutrino and antineutrino fluxes were determined using a low hadronic energy subsample of charged-current events. We report measurements of $\nu \mathrm{\text{−}}\mathrm{Fe}$ ($\overline{\nu }\mathrm{\text{−}}\mathrm{Fe}$) cross section in the energy range 3–50 GeV (5–50 GeV) with precision of 2%–8% (3%–9%) and their ratio which is measured with precision 2%–8%. The data set spans the region from low energy, where accurate measurements are sparse, up to the high-energy scaling region where the cross section is well understood.

We calculate the long-range interactions between two simple branes placed parallel at a separation in diverse dimensions via an effective field theory approach. We also compute the explicit long-range interaction between two $D$-branes with each carrying a world volume non-Abelian magnetic flux in three special cases, respectively. In particular, we demonstrate that the half-string creation between a $D_0$-brane and a $D_8$-brane continues to hold even in the present context, therefore lending further support to the previous assertion of this. Our computations also raise the issue in one case on whether a constructed ($D_0,D_8$) bound state is actually a marginal one.

We study renormalization group flows in the Lifshitz-like $N$-flavor four-Fermi model discussed in [Phys. Rev. D 80, 105018 (2009)]. In the large-$N$ limit, a nontrivial flow occurs in only one of all possible marginal couplings and one relevant coupling, which provides the scale for Lorentz invariance violations. We discuss in detail the phase diagram and renormalization group flows in the space of couplings, which includes the Lifshitz fixed point, the free field fixed point and a new fixed point characterized by $z=1$ scaling and a violation of Lorentz invariance, which cannot be tuned away by adjusting a parameter. In the broken symmetry phase, the model flows from the $z=3$ Lifshitz-like fixed point in the ultraviolet to this new fixed point in the infrared. However, in a modified version of the present model, which has an effective ultraviolet cutoff much smaller than the Lorentz invariance violating scale, the infrared behavior is governed by an approximately Lorentz invariant theory, similar to the low-energy limit of the usual relativistic Nambu–Jona-Lasinio model. Such a modified model could be realized by a supersymmetric version of the present model, if it exists.

We evaluate the neutrino fluxes to be expected from neutralino lightest supersymmetric particle (LSP) annihilations inside the Sun, within the minimal supersymmetric extension of the standard model with supersymmetry-breaking scalar and gaugino masses constrained to be universal at the grand unified theory scale [the constrained minimal supersymmetric standard model (CMSSM)]. We find that there are large regions of typical CMSSM $(m_{1/2},m_0)$ planes where the LSP density inside the Sun is not in equilibrium, so that the annihilation rate may be far below the capture rate. We show that neutrino fluxes are dependent on the solar model at the 20% level, and adopt the AGSS09 model of Serenelli et al. for our detailed studies. We find that there are large regions of the CMSSM $(m_{1/2},m_0)$ planes where the capture rate is not dominated by spin-dependent LSP-proton scattering, e.g., at large $m_{1/2}$ along the CMSSM coannihilation strip. We calculate neutrino fluxes above various threshold energies for points along the coannihilation/rapid-annihilation and focus-point strips where the CMSSM yields the correct cosmological relic density for $\tan \beta =10$ and 55 for $\mu >0$, exploring their sensitivities to uncertainties in the spin-dependent and -independent scattering matrix elements. We also present detailed neutrino spectra for four benchmark models that illustrate generic possibilities within the CMSSM. Scanning the cosmologically favored parts of the parameter space of the CMSSM, we find that the IceCube/DeepCore detector can probe at best only parts of this parameter space, notably the focus-point region and possibly also at the low-mass tip of the coannihilation strip.

An approximation to general relativity is presented that agrees with the Einstein field equations up to and including the fourth post-Newtonian (PN) order. This approximation is formulated in a fully constrained scheme: all involved equations are explicitly elliptic except the wave equation that describes the two independent degrees of freedom of the gravitational field. The formalism covers naturally the conformal-flat condition approach by Isenberg, Wilson, and Mathews and the improved second PN-order exact approach conformal-flat condition plus. For stationary configurations, like Kerr black holes, agreement with general relativity is achieved even through 5PN order. In addition, a particularly interesting 2PN-exact waveless approximation is analyzed in detail, which results from imposing more restrictive conditions. The proposed scheme can be considered as a further development on the waveless approach suggested by Schäfer and Gopakumar [26].

We derive conserved charges as quasilocal Hamiltonians by covariant phase space methods for a class of geometric Lagrangians that can be written in terms of the spin connection, the vielbein, and possibly other tensorial form fields, allowing also for nonzero torsion. We then recalculate certain known results and derive some new ones in three to six dimensions hopefully enlightening certain aspects of all of them. The quasilocal energy is defined in terms of the metric and not its first derivatives, requiring “regularization” for convergence in most cases. Counterterms consistent with Dirichlet boundary conditions in first order formalism are shown to be an efficient way to remove divergencies and derive the values of conserved charges, the clear-cut application being metrics with anti–de Sitter (or de Sitter) asymptotics. The emerging scheme is: all is required to remove the divergencies of a Lovelock gravity is a boundary Lovelock gravity.

We study cosmological perturbations in Hořava-Lifshitz Gravity, a recently proposed potentially ultraviolet-complete quantum theory of gravity. We consider scalar metric fluctuations about a homogeneous and isotropic space-time. Starting from the most general metric, we work out the complete second order action for the perturbations. We then make use of the residual gauge invariance and of the constraint equations to reduce the number of dynamical degrees of freedom. At first glance, it appears that there is an extra scalar metric degree of freedom. However, introducing the Sasaki-Mukhanov variable, the combination of spatial metric fluctuation and matter inhomogeneity for which the action in general relativity has canonical form, we find that this variable has the standard time derivative term in the second order action, and that the extra degree of freedom is nondynamical. The limit $\lambda \to 1$ is well behaved, unlike what is obtained when expanding about Minkowski space-time. Thus, there is no strong coupling problem for Hořava-Lifshitz gravity when considering cosmological solutions. We also compute the spectrum of cosmological perturbations. If the potential in the action is taken to be of “detailed balance” form, we find a cancellation of the highest derivative terms in the action for the curvature fluctuations. As a consequence, the initial spectrum of perturbations will not be scale-invariant in a general space-time background, in contrast to what happens when considering Hořava-Lifshitz matter leaving the gravitational sector unperturbed. However, if we break the detailed balance condition, then the initial spectrum of curvature fluctuations is indeed scale-invariant on ultraviolet scales. As an application, we consider fluctuations in an inflationary background and draw connections with the “trans-Planckian problem” for cosmological perturbations. In the special case in which the potential term in the action is of detailed balance form and in which $\lambda =1$, the equation of motion for cosmological perturbations in the far UV takes the same form as in general relativity. However, in general the equation of motion is characterized by a modified dispersion relation.

We reveal the center vortex content of $SU(2)$ calorons and ensembles of them. We use Laplacian center gauge as well as maximal center gauges to show that the vortex in a single caloron consists of two parts. The first one connects the constituent dyons of the caloron (which are monopoles in Laplacian Abelian gauge) and extends in time. The second part is predominantly spatial, encloses one of the dyons and can be related to the twist in the caloron gauge field. This part depends strongly on the caloron holonomy and degenerates to a plane when the holonomy is maximally nontrivial, i.e. when the asymptotic Polyakov loop is traceless. Correspondingly, we find the spatial vortices in caloron ensembles to percolate in this case. This finding fits perfectly in the confinement scenario of vortices and shows that calorons are suitable to facilitate the vortex confinement mechanism.