We investigate the effects of viscosity terms depending on the Hubble parameter and its derivatives in the dark energy equation of state. Such terms are possible if dark energy is a fictitious fluid originating from corrections to the Einstein general relativity as is the case for some braneworld inspired models or fourth order gravity. We consider two classes of models whose singularities in the early and late time universe have been studied by testing the models against the dimensionless coordinate distance to Type Ia Supernovae and radio galaxies also including priors on the shift and the acoustic peak parameters. It turns out that both models are able to explain the observed cosmic speed up without the need of phantom ($w<-1$) dark energy.

Bounds on masses and abundances of Strange Quark Nuggets (SQNs) are inferred from a seismic search on Earth. Potential SQN bounds from a possible seismic search on the Moon are reviewed and compared with Earth capabilities. Bounds are derived from the data taken by seismometers implanted on the Moon by the Apollo astronauts. We show that the Apollo data implies that the abundance of SQNs in the region of 10 kg to 1 ton must be at least an order of magnitude less than would saturate the dark matter in the solar neighborhood.

Gauge coupling unification and the success of TeV-scale weakly-interacting dark matter are usually taken as evidence of low-energy supersymmetry (SUSY). However, if we assume that the tuning of the Higgs can be explained in some unnatural way, from environmental considerations for example, SUSY is no longer a necessary component of any beyond the standard model theory. In this paper we study the minimal model with a dark matter candidate and gauge coupling unification. This consists of the standard model plus fermions with the quantum numbers of SUSY Higgsinos, and a singlet. It predicts thermal dark matter with a mass that can range from 100 GeV to around 2 TeV and generically gives rise to an electric dipole moment (EDM) that is just beyond current experimental limits, with a large portion of its allowed parameter space accessible to next-generation EDM and direct detection experiments. We study precision unification in this model by embedding it in a 5D orbifold GUT where certain large threshold corrections are calculable, achieving gauge coupling and $b–\tau$ unification, and predicting a rate of proton decay just beyond current limits.

We update our analysis of technicolor theories with techniquarks in higher dimensional representations of the technicolor gauge group in the light of the new electroweak precision data on the $Z$ resonance.

In the context of brane-world scenarios, we study the effects produced by the exchange of virtual massive branons. A one-loop calculation is performed which generates higher-dimensional operators involving SM fields suppressed by powers of the brane tension scale. We discuss constraints on this scenario from colliders such as HERA, LEP and Tevatron and prospects for future detections at LHC or ILC. The most interesting phenomenology comes from new four-particles vertices induced by branon radiative corrections, mainly from four-fermion interactions. The presence of flexible branes modifies also the muon anomalous magnetic moment and the electroweak precision observables.

We study spin $1/2$ isoscalar and isovector, even and odd parity candidates for the ${\Theta }^{+}(1540)$ pentaquark particle using large scale lattice QCD simulations. Previous lattice works led to inconclusive results because so far it has not been possible to unambiguously identify the known scattering spectrum and tell whether additionally a genuine pentaquark state also exists. Here we carry out this analysis using several possible wave functions (operators). Linear combinations of those have a good chance of spanning both the scattering and pentaquark states. Our operator basis is the largest in the literature, and it also includes spatially nontrivial ones with unit orbital angular momentum. The cross correlator we compute is $14\times 14$ with 60 nonvanishing elements. We can clearly distinguish the lowest scattering state(s) in both parity channels up to above the expected location of the pentaquark, but we find no trace of the latter. Based on that we conclude that there are most probably ($\approx 2\sigma /6\sigma$ levels in the negative/positive parity channels) no pentaquark bound states at our quark masses, corresponding to $m_{\pi }=400–630\mathrm{MeV}$. However, we cannot rule out the existence of a pentaquark state at the physical quark mass corresponding to $m_{\pi }=135\mathrm{MeV}$ or pentaquarks with a more exotic wave function.

A theoretical framework is suggested for the calculation of ${\gamma }^{*}N\to \Delta$ transition form factors using the light-cone sum rule approach. Leading-order sum rules are derived and compared with the existing experimental data. We find that the transition form factors in a several GeV region are dominated by the soft contributions that can be thought of as overlap integrals of the valence components of the hadron wave functions. The minus components of the quark fields contribute significantly to the result, which can be reinterpreted as large contributions of the quark orbital angular momentum.

This article presents a measurement of the top quark mass using the CDF II detector at Fermilab. Colliding beams of protons and antiprotons at Fermilab’s Tevatron ($\sqrt{s}=1.96\mathrm{TeV}$) produce top/antitop pairs, which decay to $W^{+}{W}^{-}b\overline{b}$; events are selected where one $W$ decays to hadrons and the other $W$ decays to either $e$ or $\mu$ plus a neutrino. The data sample corresponds to an integrated luminosity of approximately $318{\mathrm{pb}}^{-1}$. A total of 165 $t\overline{t}$ events are separated into four subsamples based on jet transverse energy thresholds and the number of $b$ jets identified by reconstructing a displaced vertex. In each event, the reconstructed top quark invariant mass is determined by minimizing a ${\chi }^2$ for the overconstrained kinematic system. At the same time, the mass of the hadronically decaying $W$ boson is measured in the same event sample. The observed $W$ boson mass provides an in situ improvement in the determination of the hadronic jet energy scale. A simultaneous likelihood fit of the reconstructed top quark masses and the $W$ boson invariant masses in the data sample to distributions from simulated signal and background events gives a top quark mass of ${173.5}_{-3.8}^{+3.9}\mathrm{GeV}/c^2$.

We investigate a possibility of neutralino dark matter (DM) direct detection in the future electron accelerators. That is counting of high $p_T$ electron recoil events by neutralinos in halo. If selectron and neutralino masses would be precisely measured in future collider experiments, the beam energy could be tuned so that the scatterings are dominated by on-pole selectron exchange. When selectron and neutralino mass difference is smaller than $O(10)$ GeV, the elastic cross section exceeds over micro barn. Discovery of the high $p_T$ electron events would be a firm prove of the neutralino DM component in halo. In the experiment, the electron beam energy must be tuned within $O(10)$ MeV and the electron beam with high currents of $O(100)A$ is required for the detectors of the total length of a few hundred meters so that the sufficient event rate is obtained. The dependence of the event rate on the DM velocity distribution in halo is also discussed. This method might be applicable to other DM candidates.

We study dyonic solutions to the gravity-dilaton-antisymmetric form equations with the goal of identifying new $p$-brane solutions on the fluxed linear dilaton background. Starting with the generic solutions constructed by reducing the system to decoupled Liouville equations for certain values of parameters, we identify the most general solution whose singularities are hidden behind a regular event horizon, and then explore the admissible asymptotic behaviors. In addition to known asymptotically flat dyonic branes, we find two classes of asymptotically nonflat solutions which can be interpreted as describing magnetically charged branes on the electrically charged linear dilaton background (and the $S$-dual configuration of electrically charged branes on the magnetically charged background), and uncharged black branes on the dyonically charged linear dilaton background. This interpretation is shown to be consistent with the first law of thermodynamics for the new solutions.

The effects of the initial temperature in the out of equilibrium quantum field dynamics in the presence of a homogeneous external field are investigated. We consider an initial thermal state of temperature $T$ for a constant external field $\overrightarrow{J}$. A subsequent sign flip of the external field, $\overrightarrow{J}\to -\overrightarrow{J}$, gives rise to an out of equilibrium nonperturbative quantum field dynamics. The dynamics is studied here for the symmetry broken $\lambda ({\overrightarrow{\Phi }}^2{)}^2$ scalar $N$ component field theory in the large $N$ limit. We find a dynamical effective potential for the expectation value that helps us to understand the dynamics. The dynamics presents two regimes defined by the presence or absence of a temporal trapping close to the metastable equilibrium position of the potential. The two regimes are separated by a critical value of the external field that depends on the initial temperature. The temporal trapping is shorter for larger initial temperatures or larger external fields. Parametric resonances and spinodal instabilities amplify the quantum fluctuations in the field components transverse to the external field. When there is a temporal trapping, this is the main mechanism that allows the system to escape from the metastable state for large $N$. Subsequently, backreaction stops the growth of the quantum fluctuations and the system enters a quasiperiodic regime.

We consider U(1) gauge fields in a slice of ${\mathrm{AdS}}_5$ with bulk and boundary mass parameters. The zero mode of a bulk U(1) gauge field can be localized either on the UV or IR brane. This leads to a simple model of millicharged particles in which fermions can have arbitrarily small electric charge. In the electroweak sector we also discuss phenomenological implications of a localized $\mathrm{U}(1{)}_Y$ gauge boson. Using the AdS/CFT correspondence we present the 4D holographic interpretation of the 5D model. In particular the photon is shown to be a composite particle when localized near the IR brane, whereas it is elementary when localized near the UV brane. In the dual interpretation the millicharge results from an elementary fermion coupling to a composite photon via a vector current with large anomalous dimension.

Affleck-Dine baryogenesis in models where the gravitino is both the lightest supersymmetric particle and the dark matter candidate is investigated. For a high enough reheating temperature to produce sufficient gravitinos by thermal processes, the observed baryon asymmetry can be explained by Affleck-Dine baryogenesis as well as thermal leptogenesis. On the other hand, if the reheating temperature is not high enough, most of the gravitinos must be produced by the decay of the next-to-lightest supersymmetric particle (NSP). Particularly, in the case where Q-balls cannot survive the evaporation, the gravitino number density is given by the NSP’s thermal relic density. Interestingly, if Q-balls survive, they can be a source of gravitinos via the NSP decay. Then, we could find a new cosmological interesting region in parameter space because the gravitino number density does not relate to the NSP’s thermal relic density.

We discuss the production of cosmogenic neutrinos on extragalactic infrared photons in a model of its cosmological evolution. The relative importance of these infrared photons as a target for proton interactions is significant, especially in the case of steep injection spectra of the ultrahigh energy cosmic rays. For an $E^{-2.5}$ cosmic ray injection spectrum, for example, the event rate of neutrinos of energy above 1 PeV is more than doubled.

Rates of coherent neutrino-nucleus elastic scattering at a high-intensity stopped-pion neutrino source in various detector materials (relevant for novel low-threshold detectors) are calculated. Sensitivity of a coherent neutrino-nucleus elastic scattering experiment to new physics is also explored.

In the real time formulation of finite temperature field theories, one introduces an additional set of fields (type-2 fields) associated to each field in the original theory (type-1 field). In [J.  M. Maldacena, J. High Energy Phys. 04 (2003) 021.], in the context of the anti-de Sitter (AdS)-conformal field theories (CFT) correspondence, Maldacena interpreted type-2 fields as living on a boundary behind the black hole horizon. However, below the Hawking-Page transition temperature, the thermodynamically preferred configuration is the thermal AdS without a black hole, and hence there are no horizon and boundary behind it. This means that when the dual gauge theory is in confined phase, the type-2 fields cannot be associated with the degrees of freedom behind the black hole horizon. I argue that in this case the role of the type-2 fields is to make up bulk type-2 fields of classical closed string field theory on AdS at finite temperature in the real time formalism.

We present a numerical study of the evolution of a nonlinearly disturbed black hole described by the Bondi-Sachs metric, for which the outgoing gravitational waves can readily be found using the news function. We compare the gravitational-wave output obtained with the use of the news function in the Bondi-Sachs framework, with that obtained from the Weyl scalars, where the latter are evaluated in a quasi-Kinnersley tetrad. The latter method has the advantage of being applicable to any formulation of Einstein’s equations—including the ADM formulation and its various descendants—in addition to being robust. Using the nonlinearly disturbed Bondi-Sachs black hole as a test bed, we show that the two approaches give wave-extraction results which are in very good agreement. When wave extraction through the Weyl scalars is done in a non-quasi-Kinnersley tetrad, the results are markedly different from those obtained using the news function.

We study the evaporation of black holes in noncommutative space-times. We do this by calculating the correction to the detector’s response function for a moving mirror in terms of the noncommutativity parameter $\Theta$ and then extracting the number density as modified by this parameter. We find that allowing space and time to be noncommutative increases the decay rate of a black hole.

A class of exact solutions of the Einstein–Maxwell equations is presented which describes an accelerating and rotating charged black hole in an asymptotically de Sitter or anti-de Sitter universe. The metric is presented in a new and convenient form in which the meaning of the parameters is clearly identified, and from which the physical properties of the solution can readily be interpreted.

Abandoning the perfect fluid hypothesis, we investigate here the possibility that the dark energy equation of state (EoS) $w$ is a nonlinear function of the energy density $\rho$. To this aim, we consider four different EoS describing classical fluids near thermodynamical critical points and discuss the main features of cosmological models made out of dust matter and a dark energy term with the given EoS. Each model is tested against the data on the dimensionless coordinate distance to Type Ia Supernovae and radio galaxies, the shift and the acoustic peak parameters and the positions of the first three peaks in the anisotropy spectrum of the comic microwave background radiation. We propose a possible interpretation of each model in the framework of scalar field quintessence determining the shape of the self-interaction potential $V(\varphi )$ that gives rise to each one of the considered thermodynamical EoS. As a general result, we demonstrate that replacing the perfect fluid EoS with more general expressions gives both the possibility of successfully solving the problem of cosmic acceleration escaping the resort to phantom models.