We study the general properties of attractors in a cosmological model with tachyonic potential and a scalar field nonminimally coupled to matter. In the conventional approach to the stability analysis the qualitative properties of the equations and of the long-term behavior of the solutions are investigated where the scaling solutions are the late time attractors and independent of the initial conditions. In this article, in a new approach, we examine the stability analysis of the model by simultaneously solving the dynamical system and best fitting the stability parameters with the observational data. The advantage of this approach is that the model which was of a purely mathematical nature become physically motivated. The number of the new critical points and also their properties, given in terms of the best-fitted parameters, may alter due to the best-fitting procedure. In a further step in stability analysis, we best fit both the stability parameters and initial conditions with the observational data. The results impose more constraints on the trajectories in the phase space and provide more information about the dynamics of the cosmological model.

We apply the recently extended conserved Killing charge definition of Abbott-Deser-Tekin formalism to compute, for the first time, the energies of analytic Lifshitz black holes in higher dimensions. We then calculate the temperature and the entropy of this large family of solutions, and study and discuss the first law of black hole thermodynamics. Along the way we also identify the possible critical points of the relevant quadratic curvature gravity theories. Separately, we also apply the generalized Killing charge definition to compute the energy and the angular momentum of the warped ${\mathrm{AdS}}_3$ black hole solution of the three-dimensional new massive gravity theory.

The differential equations, which are used for matter perturbations, are usually derived from the Newton gravity and the Euler equation in the expanded universe. In this paper, by the explicit calculations of metric perturbation theory in $\Lambda \mathrm{CDM}$ model, we derive the general relativistic corrections exactly for the equations and show that the differential equations derived from the Newton gravity and the Euler equation are valid in the small scale region from nonrelativistic matter dominant era onwards. However, the corrections are not negligible in radiation dominant era.

In the Cadassian universe, one can explain the acceleration of the universe without introducing a dark energy component. However, it is hard to get the dynamical equations of this model from the action principle. Recently, works on the relation between thermodynamics and gravity indicate that gravity force may not be a fundamental force. In this paper, we shall study the thermodynamics of the Cardassian universe, and it might be the origin of this cosmological model. We find that the corresponding entropy obeys ordinary area law when the area of the trapping horizon is small, and it becomes a constant when the area is going to be large in the original and modified polytropic Cardassian models, while it has a maximum value in the exponential one. It seems that the Cardassian universe only contains finite information according to the holographic principle, which states that all the information in the bulk should be encoded on the boundary of the bulk.

A model is presented in the philosophy of the “String Axiverse” of [A. Arvanitaki, S. Dimopoulos, S. Dubovsky, N. Kaloper, and J. March-Russell, Phys. Rev. D 81, 123530 (2010).] that incorporates a coupling of ultralight axions to their corresponding moduli through the mass term. The light fields roll in their potentials at late times and contribute to the dark sector energy densities in the cosmological expansion. The addition of a coupling and extra field greatly enrich the possible phenomenology of the axiverse. There are a number of interesting phases where the axion and modulus components behave as dark matter or dark energy and can have considerable and distinct effects on the expansion history of the universe by modifying the equation of state in the past or causing possible future collapse of the universe. In future such a coupling may help to alleviate fine tuning problems for cosmological axions. We motivate and present the model, and briefly explore its cosmological consequences numerically.

We derive an exact analytical solution for the redshift evolution of linear and scale-independent bias, by solving a second-order differential equation based on linear perturbation theory. This bias evolution model is applicable to all different types of dark energy and modified gravity models. We propose that the combination of the current bias evolution model with data on the bias of extragalactic mass tracers could provide an efficient way to discriminate between geometrical dark energy models and dark energy models that adhere to general relativity.

We present a new complete analysis of the electroweak precision observables within the recently proposed 4-site Higgsless model, which is based on the $SU(2{)}_L\times SU(2{)}_1\times SU(2{)}_2\times U(1{)}_Y$ gauge symmetry and predicts six extra gauge bosons, $W_{1,2}^{\pm }$ and $Z_{1,2}$. Within the ${\epsilon }_i$ ($i=1$, 2, 3, $b$) parametrization, we compute for the first time the electroweak precision test bounds via a complete numerical algorithm going beyond commonly used approximations. Both ${\epsilon }_{1,3}$ impose strong constraints. Hence, it is mandatory to consider them jointly when extracting electroweak precision test bounds and to fully take into account the correlations among the electroweak precision measurements. The phenomenological consequence is that the extra gauge bosons must be heavier than 250 GeV. Their couplings to SM fermions, even if bounded, might be of the same order of magnitude than the SM ones. In contrast to other Higgsless models, the 4-site model is not fermiophobic. The new gauge bosons could thus be discovered in the favored Drell-Yan channel already during the present run of the LHC experiment.

Unless the scale of electroweak symmetry breaking is stabilized dynamically, most of the universes in a multiverse theory will lack an observable weak nuclear interaction. Such “weakless universes” could support intelligent life based on organic chemistry, as long as other parameters are properly adjusted. By taking into account the seemingly unrelated flavor dynamics that address the hierarchy of quark masses and mixings, we show that such weakless (but hospitable) universes can be far more common than universes like ours. The gauge hierarchy problem therefore calls for a dynamical (rather than anthropic) solution.

Alignment of the main energy fluxes along a straight line in a target plane has been observed in families of cosmic ray particles detected in the Pamir mountains. The fraction of events with alignment is statistically significant for families with superhigh energies and large numbers of hadrons. This can be interpreted as evidence for coplanar hard scattering of secondary hadrons produced in the early stages of the atmospheric cascade development. This phenomenon can be described within the recently proposed “crystal world,” with latticized and anisotropic spatial dimensions. Planar events are expected to dominate particle collisions at a hard-scattering energy exceeding the scale ${\Lambda }_3$ at which space transitions from $3\mathrm{D}\rightleftharpoons 2\mathrm{D}$. We study specific collider signatures that will test this hypothesis. We show that the energy spectrum of Drell-Yan (DY) scattering is significantly modified in this framework. At the LHC, two jet and three jet events are necessarily planar, but four jet events can test the hypothesis. Accordingly, we study in a model-independent way the $5\sigma$ discovery reach of the ATLAS and CMS experiments for identifying four jets coplanarities. For the extreme scenario in which all $pp\to 4$ jet scattering processes become coplanar above ${\Lambda }_3$, we show that with an integrated luminosity of $10(100){\mathrm{fb}}^{-1}$ the LHC experiments have the potential to discover correlations between jets if ${\Lambda }_3\lesssim 1.25(1.6)\mathrm{TeV}$.

We study momentum distributions of the final-state charged lepton in $p\overline{p}/pp\to t\overline{t}\to {\ell }^{+}X(\ell =e\mathrm{\text{or}}\mu )$ at hadron colliders, i.e., Tevatron and Large Hadron Collider (LHC), in order to explore possible new-physics effects in the top-quark sector. Assuming general model-independent $t\overline{t}g+t\overline{t}gg$ and $tbW$ interactions beyond the standard model, we first derive analytical formulas for the corresponding parton-parton processes. We then compute the lepton angular, energy, and transverse-momentum distributions in $p\overline{p}/pp$ collisions to clarify how they are affected by those anomalous couplings.

We present results for leading-twist azimuthal asymmetries in semi-inclusive lepton-nucleon deep-inelastic scattering due to naive time-reversal odd transverse-momentum-dependent parton distribution functions from the light-cone constituent-quark model. We carefully discuss the range of applicability of the model, especially with regard to positivity constraints and evolution effects. We find good agreement with available experimental data from COMPASS and HERMES, and present predictions to be tested in forthcoming experiments at Jefferson Lab.

We assess the current phenomenological status of transverse momentum dependent (TMD) parton distribution functions (PDFs) and fragmentation functions (FFs) and study the effect of consistently including perturbative QCD (pQCD) evolution. Our goal is to initiate the process of establishing reliable, QCD-evolved parametrizations for the TMD PDFs and TMD FFs that can be used both to test TMD factorization and to search for evidence of the breakdown of TMD factorization that is expected for certain processes. In this article, we focus on spin-independent processes because they provide the simplest illustration of the basic steps and can already be used in direct tests of TMD factorization. Our calculations are based on the Collins-Soper-Sterman (CSS) formalism, supplemented by recent theoretical developments which have clarified the precise definitions of the TMD PDFs and TMD FFs needed for a valid TMD-factorization theorem. Starting with these definitions, we numerically generate evolved TMD PDFs and TMD FFs using as input existing parametrizations for the collinear PDFs, collinear FFs, nonperturbative factors in the CSS factorization formalism, and recent fixed-scale fits. We confirm that evolution has important consequences, both qualitatively and quantitatively, and argue that it should be included in future phenomenological studies of TMD functions. Our analysis is also suggestive of extensions to processes that involve spin-dependent functions such as the Boer-Mulders, Sivers, or Collins functions, which we intend to pursue in future publications. At our website [http://projects.hepforge.org/tmd/], we have made available the tables and calculations needed to obtain the TMD parametrizations presented herein.

Motivated by the accumulating hints of new sterile neutrino species at the eV scale, we explore the consequences of such an hypothesis on the solar sector phenomenology. After introducing the theoretical formalism needed to describe the Mikheyev-Smirnov-Wolfenstein conversion of solar neutrinos in the presence of one (or more) sterile neutrino state(s) located “far” from the (${\nu }_1$, ${\nu }_2$) “doublet”, we perform a quantitative analysis of the available experimental results, focusing on the electron neutrino mixing. We find that the present data posses a sensitivity to the amplitude of the lepton mixing matrix element $U_{e4}$—encoding the admixture of the electron neutrino with a new mass eigenstate—which is comparable to that achieved on the standard matrix element $U_{e3}$. In addition, and more importantly, our analysis evidences that, in a 4-flavor framework, the current preference for $|U_{e3}|\ne 0$ is indistinguishable from that for $|U_{e4}|\ne 0$, having both a similar statistical significance (which is $\sim 1.3\sigma$ adopting the old reactor fluxes determinations, and $\sim 1.8\sigma$ using their new estimates.) We also point out that, differently from the standard 3-flavor case, in a $3+1$ scheme the Dirac $CP$-violating phases cannot be eliminated from the description of solar neutrino conversions.

The equations of motion and the Bianchi identity of the C-field in M-theory are encoded in terms of the signature operator. We then reformulate the topological part of the action in M-theory using the signature, which leads to connections to the geometry of the underlying manifold, including positive scalar curvature. This results in a variation on the miraculous cancellation formula of Alvarez-Gaumé and Witten in 12 dimensions and leads naturally to the Kreck-Stolz $s$-invariant in 11 dimensions. Hence M-theory detects the diffeomorphism type of 11-dimensional (and seven-dimensional) manifolds and in the restriction to parallelizable manifolds classifies topological 11 spheres. Furthermore, requiring the phase of the partition function to be anomaly-free imposes restrictions on allowed values of the $s$-invariant. Relating to string theory in ten dimensions amounts to viewing the bounding theory as a disk bundle, for which we study the corresponding phase in this formulation.

We present the covariant symplectic structure of the Topologically Massive Gravity and find a compact expression for the conserved charges of generic spacetimes with Killing symmetries.

We present a numerical code for calculating the self-force on a scalar charge moving in a bound (eccentric) geodesic in the equatorial plane of a Kerr black hole. We work in the frequency domain and make use of the method of extended homogeneous solutions [Phys. Rev. D 78, 084021 (2008)], in conjunction with mode-sum regularization. Our work is part of a program to develop a computational architecture for fast and efficient self-force calculations, alternative to time-domain methods. We find that our frequency-domain method outperforms existing time-domain schemes for small eccentricities, and, remarkably, remains competitive up to eccentricities as high as $\sim 0.7$. As an application of our code, we (i) compute the conservative scalar-field self-force correction to the innermost stable circular equatorial orbit, as a function of the Kerr spin parameter; and (ii) calculate the variation in the rest mass of the scalar particle along the orbit, caused by the component of the self-force tangent to the four-velocity.

Recently it was shown that quantum corrections to the Newton potential can explain the rotation curves in spiral galaxies without introducing the dark matter halo. The unique phenomenological parameter $\alpha \nu$ of the theory grows with the mass of the galaxy. In order to better investigate the mass-dependence of $\alpha \nu$ one needs to check the upper bound for $\alpha \nu$ at a smaller scale. Here we perform the corresponding calculation by analyzing the dynamics of the Laplace-Runge-Lenz vector. The resulting limitation on quantum corrections is quite severe, suggesting a strong mass-dependence of $\alpha \nu$.

By gauging the Maxwell spacetime algebra, the standard geometric framework of Einstein gravity with cosmological constant term is extended by adding six four-vector fields $A_{\mu }^{ab}(x)$ associated with the six Abelian tensorial charges in the Maxwell algebra. In the simplest Maxwell extension of Einstein gravity this leads to a generalized cosmological term that includes a contribution from these vector fields. We also consider going beyond the basic gravitational model by means of bilinear actions for the new Abelian gauge fields. Finally, an analogy with the supersymmetric generalization of gravity is indicated. In an appendix, we propose an equivalent description of the model in terms of a shift of the standard spin connection by the $A_{\mu }^{ab}(x)$ fields.

We develop a scenario whereby monopoles in a hidden sector yield a decaying dark matter candidate of interest for the PAMELA and FERMI $e^{\pm }$ excesses. The monopoles are not completely hidden due to a very small kinetic mixing and a hidden photon mass. The latter also causes the monopoles and antimonopoles to be connected by strings. The resulting long-lived objects eventually decay to hidden photons which tend to escape galactic cores before decaying. The mass scales are those of the hidden photon ($\approx 500\mathrm{MeV}$), the monopole ($\approx 3\mathrm{TeV}$) and the mixing scale (close to the Planck scale). A gauge coupling in the hidden sector is the only other parameter. This coupling must be strong and this results in light pointlike monopoles and light thin strings.

We present a detailed calculation of our previous short paper [M. Shiraishi, D. Nitta, S. Yokoyama, K. Ichiki, and K. Takahashi, Phys. Rev. D 82, 121302 (2010).] in which we have investigated a constraint on the magnetic field strength through comic microwave background temperature bispectrum of vector modes induced from primordial magnetic fields. By taking into account full angular dependence of the bispectrum with spin spherical harmonics and Wigner symbols, we explicitly show that the cosmic microwave background bispectrum induced from the statistical-isotropic primordial vector fluctuations can be also described as an angle-averaged form in the rotationally invariant way. We also study the cases with different spectral indices of the power spectrum of the primordial magnetic fields.