I present results for the top quark rapidity distribution at Large Hadron Collider and Tevatron energies, including higher-order corrections from threshold resummation. Approximate next-to-next-to-leading-order (NNLO) results are obtained by adding the NNLO soft-gluon corrections at next-to-next-to-leading-logarithm level to the exact next-to-leading-order calculation. Theoretical predictions are shown for the rapidity distribution, including the scale dependence of the distributions. The forward-backward asymmetry at the Tevatron is also calculated.

We evaluate the drag and diffusion coefficients of a hot hadronic medium consisting of pions, nucleons, kaons, and eta using open charm mesons as a probe. The interaction of the probe with the hadronic matter has been treated in the framework of effective field theory. It is observed that the magnitude of both the transport coefficients are significant, indicating a substantial amount of interaction of the heavy mesons with the thermal hadronic system. The results may have noticeable impact on the experimental observables like the suppression of single electron spectra originating from the decays of heavy mesons in nuclear collisions at relativistic energies.

We investigate tensor modes in inflationary scenarios from the point of view of Ashtekar variables and their generalizations labeled by Immirzi parameter $\gamma$, which we will assume imaginary. Being careful to properly define the classical perturbed Hamiltonian by taking several subtleties into account, we reproduce, on shell, the usual expression found in cosmological perturbation theory. However the quantum Hamiltonian displays significant differences, namely, in the vacuum energy and fluctuations of the various modes. We can identify combinations of metric and connection variables representing graviton states, noting that before reality conditions are imposed there are gravitons and antigravitons. It turns out that half of these modes have negative energy but after defining the inner product we conclude that they are nonphysical and should be selected out. We are left with the usual graviton modes but with a chiral asymmetry in the vacuum energy and fluctuations. The latter depends on $\gamma$ and on the ordering prescription (namely in the Hamiltonian constraint). Such an effect would leave a distinctive imprint in the polarization of the cosmic microwave background, thus finally engaging quantum gravity in meaningful experimental test.

Recently proposed “critical” higher-derivative gravities in ${\mathrm{AdS}}_D$ $D>3$ are expected to carry logarithmic representation of the anti-de Sitter isometry group. In this article, we quantize linear fluctuations of these critical gravities, which are known to be either identical with linear fluctuations of Einstein’s gravity or satisfy logarithmic boundary conditions at spacial infinity. We identify the scalar product uniquely defined by the symplectic structure implied by the classical action, and show that it does not posses null vectors. Instead, we show that the scalar product between any two Einstein modes vanishes, while the scalar product of an Einstein mode with a logarithmic mode is generically nonzero. This is the basic property of logarithmic representation that makes them neither unitary nor unitarizable.

We study characters of recent type Ia supernova data using evolving dark energy models with changing equation-of-state parameter $w$. We consider a sudden-jump approximation of $w$ for some chosen redshift spans with double transitions and constrain these models based on the Markov chain Monte Carlo method using the type Ia supernova data (Constitution, Union, Union2), together with the baryon acoustic oscillation $A$ parameter and the cosmic microwave background shift parameter in a flat background. In the double-transition model, the Constitution data shows deviation outside $1\sigma$ from the $\Lambda$ cold dark matter ($\Lambda \mathrm{CDM}$) model at low ($z\lesssim 0.2$) and middle ($0.2\lesssim z\lesssim 0.4$) redshift bins, whereas no such deviations are noticeable in the Union and Union2 data. By analyzing the Union members in the Constitution set, however, we show that the same difference is actually due to different calibration of the same Union sample in the Constitution set and is not due to new data added in the Constitution set. All detected deviations are within $2\sigma$ from the $\Lambda \mathrm{CDM}$ world model. From the $\Lambda \mathrm{CDM}$ mock data analysis, we quantify biases in the dark energy equation-of-state parameters induced by insufficient data with inhomogeneous distribution of data points in the redshift space and distance modulus errors. We demonstrate that the location of the peak in the distribution of arithmetic means (computed from the Markov chain Monte Carlo chain for each mock data) behaves as an unbiased estimator for the average bias, which is valid even for nonsymmetric likelihood distributions.

Weak bases of flavors $(u,c)$, $(d,s)$, $(e,\mu )$, and $({\nu }_e,{\nu }_{\mu })$ are assumed as the $S_3$ doublet, and $t$, $b$, $\tau$, and ${\nu }_{\tau }$ are the $S_3$ singlet; further, there are assumed $S_3$ doublet Higgs $(H_1,H_2)$ and $S_3$ singlet Higgs $H_S$. We suggest an $S_3$ invariant model in which the Yukawa interactions constructed from these $S_3$ doublets and singlets are $S_3$ invariant. In this model, we can explain the quark sector mass hierarchy, quark mixing $V_{\mathrm{CKM}}$, and the measure of $CP$ violation naturally. In the leptonic sector, neutrino masses are assumed to be constructed through the seesaw mechanism from the Majorana mass. The tri-bimaximal–like character of neutrino mixing $V_{\mathrm{MNS}}$ can be explained dynamically without any other symmetry restrictions. It is predicted that a quasidegenerate mass spectroscopy of neutrino is favorable, and values of $|V_{\mathrm{MNS}}{|}_{13}$, the $CP$ violation invariant measure $J$, and the effective Majorana mass $|⟨m⟩|$ in $(\beta \beta {)}_{0\nu }$ are not so tiny.

Supersymmetry has often been invoked as the new physics that might reconcile the experimental muon magnetic anomaly, $a_{\mu }$, with the theoretical prediction (basing the computation of the hadronic contribution on $e^{+}{e}^{-}$ data). However, in the context of the constrained minimal supersymmetric standard model (CMSSM), the required supersymmetric contributions (which grow with decreasing supersymmetric masses) are in potential tension with a possibly large Higgs mass (which requires large stop masses). In the limit of very large $m_h$ supersymmetry gets decoupled, and the CMSSM must show the same discrepancy as the standard model with $a_{\mu }$. But it is much less clear for which size of $m_h$ does the tension start to be unbearable. In this paper, we quantify this tension with the help of Bayesian techniques. We find that for $m_h\ge 125\mathrm{GeV}$ the maximum level of discrepancy given the current data ($\sim 3.2\sigma$) is already achieved. Requiring less than $3\sigma$ discrepancy, implies $m_h\lesssim 120\mathrm{GeV}$. For a larger Higgs mass we should give up either the CMSSM model or the computation of $a_{\mu }$ based on $e^{+}{e}^{-}$; or accept living with such an inconsistency.

The leading order interaction between a Goldstone boson and a matter field is universally dominated by the Weinberg-Tomozawa term. Based on this observation, we predict a rich spectrum of bound states of a kaon and a heavy meson. We argue that, if the lifetime of an excited heavy meson is significantly longer than the range of forces, then the finite width of that state can be neglected in a first approximation. Then, the $D_{s0}^{*}(2317)$, $D_{s1}(2460)$, $D_{sJ}(2860)$ and $D_{sJ}(3040)$ are generated as $DK$, $D^{*}K$, $D_1(2420)K$ and $D^{*}(2600)K$ bound states, respectively. In addition to the remarkable agreement with the measured masses, the decay patterns of the $D_{sJ}(2860)$ and $D_{sJ}(3040)$ can also be understood. Two more $D_{sJ}$ states, and kaonic bound states with the bottom mesons as well as the doubly charmed baryon are also predicted.

We compute the next-to-leading logarithmic ultrasoft running of the spin-independent singlet potentials up to $\mathcal{O}(1/m^2)$ and the corresponding contribution to the spectrum. This includes the static energy at next-to-next-to-next-to-leading logarithmic order. As a by-product of these results, we set the stage for the complete analytic and numerical computation of the heavy quarkonium spectrum with next-to-next-to-next-to-leading logarithmic accuracy for $l\ne 0$ (angular momentum) and $s=0$ (spin) states. We also compute the next-to-next-to-next-to-next-to-leading-order ultrasoft spin-independent contribution to the heavy quarkonium mass and static energy.

The injection of secondary particles produced by dark matter (DM) annihilation at redshift $100\lesssim z\lesssim 1000$ affects the process of recombination, leaving an imprint on cosmic microwave background (CMB) anisotropies. Here we provide a new assessment of the constraints set by cosmic microwave background data on the mass and self-annihilation cross section of DM particles. Our new analysis includes the most recent WMAP (7-year) and ACT data, as well as an improved treatment of the time-dependent coupling between the DM annihilation energy with the thermal gas. We show, in particular, that the improved measurement of the polarization signal places already stringent constraints on light DM particles, ruling out “thermal” WIMPs with mass $m_{\chi }\lesssim 10\mathrm{GeV}$ annihilating into electrons and WIMPs with mass $m_{\chi }\lesssim 4\mathrm{GeV}$ annihilating into muons.

We provide a simple mechanism for reconciling the direct dark matter experimental results. We consider light asymmetric composite dark matter which scatters off nuclei via Higgs and photon exchange. We demonstrate that the interference between these two channels naturally accommodates the experimental results. We discover that this happens for a compositeness scale of the order of the electroweak. We also provide a model realization based on strong dynamics at the electroweak scale.

In this paper we present semiclassical computations of the splitting of folded spinning strings in ${\mathrm{AdS}}_3$, which may be of interest in the context of AdS/CFT duality. We start with a classical closed string and assume that it can split into two closed string fragments, if at a given time two points on it coincide in target space and their velocities agree. First we consider the case of the folded string with large spin. Assuming the formal large-spin approximation of the folded string solution in ${\mathrm{AdS}}_3$, we can completely describe the process of splitting: compute the full set of charges and obtain the string solutions describing the evolution of the final states. We find that, in this limit, the world surface does not change in the process and the final states are described by the solutions of the same type as the initial string, i.e. the formal large-spin approximation of the folded string in ${\mathrm{AdS}}_3$. Then we consider the general case—splitting of string given by the exact folded string solution. We find the expressions for the charges of the final fragments, the coordinate transformations diagonalizing them and, finally, their energies and spins. Because of the complexity of the initial string profile, we cannot find the solutions describing the evolution of the final fragments, but we can predict their qualitative behavior. We also generalize the results to include circular rotations and windings in ${\mathrm{S}}^5$.

We investigate the effects of including a quasitopological cubic curvature term to the Gauss-Bonnet action to five-dimensional Einstein gravity coupled to a Proca field and search for solutions with asymptotically Lifshitz scaling symmetry. We find that a new set of Lifshitz black hole solutions exist that are analogous to those obtained in third-order Lovelock gravity in higher dimensions. No additional matter fields are required to obtain solutions with asymptotic Lifshitz behavior, though we also investigate solutions with matter. Furthermore, we examine black hole solutions and their thermodynamics in this situation and find that a negative quasitopological term, just like a positive Gauss-Bonnet term, prevents instabilities in what are ordinarily unstable Einsteinian black holes.

We introduce a new matter action principle, with a wide range of applicability, for the Vlasov equation in terms of a conjugate pair of functions. Here we apply this action principle to the study of matter in Bianchi cosmological models in general relativity. The Bianchi models are spatially-homogeneous solutions to the Einstein field equations, classified by the three-dimensional Lie algebra that describes the symmetry group of the model. The Einstein equations for these models reduce to a set of coupled ordinary differential equations. The class A Bianchi models admit a Hamiltonian formulation in which the components of the metric tensor and their time derivatives yield the canonical coordinates. The evolution of anisotropy in the vacuum Bianchi models is determined by a potential due to the curvature of the model, according to its symmetry. For illustrative purposes, we examine the evolution of anisotropy in models with Vlasov matter. The Vlasov content is further simplified by the assumption of cold, counter-streaming matter, a kind of matter that is far from thermal equilibrium and is not describable by an ordinary fluid model nor other more simplistic matter models. Qualitative differences and similarities are found in the dynamics of certain vacuum class A Bianchi models and Bianchi type I models with cold, counter-streaming Vlasov-matter potentials analogous to the curvature potentials of corresponding vacuum models.

We have developed the formalism necessary to employ the discontinuous-Galerkin approach in general-relativistic hydrodynamics. The formalism is first presented in a general four-dimensional setting and then specialized to the case of spherical symmetry within a $3+1$ splitting of spacetime. As a direct application, we have constructed a one-dimensional code, EDGES, which has been used to assess the viability of these methods via a series of tests involving highly relativistic flows in strong gravity. Our results show that discontinuous-Galerkin methods are able not only to handle strong relativistic shock waves but, at the same time, to attain very high orders of accuracy and exponential convergence rates in smooth regions of the flow. Given these promising prospects and their affinity with a pseudospectral solution of the Einstein equations, discontinuous-Galerkin methods could represent a new paradigm for the accurate numerical modelling in relativistic astrophysics.

The asymptotics of some spin foam amplitudes for a quantum 4-simplex is known to display rapid oscillations whose frequency is the Regge action. In this paper, we reformulate this result through a difference equation, asymptotically satisfied by these models, and whose semiclassical solutions are precisely the sine and the cosine of the Regge action. This equation is then interpreted as coming from the canonical quantization of a simple constraint in Regge calculus. This suggests to lift and generalize this constraint to the phase space of loop quantum gravity parametrized by twisted geometries. The result is a reformulation of the flat model for topological BF theory from the Hamiltonian perspective. The Wheeler-DeWitt equation in the spin network basis gives difference equations which are exactly recursion relations on the 15j-symbol. Moreover, the semiclassical limit is investigated using coherent states, and produces the expected results. It mimics the classical constraint with quantized areas, and for Regge geometries it reduces to the semiclassical equation which has been introduced in the beginning.

We propose a phenomenological model for the early universe where there is a smooth transition between an early quintessence phase and a radiation-dominated era. The matter content is modeled by an appropriately modified Chaplygin gas for the early universe. We constrain the model observationally by mapping the primordial power spectrum of the scalar perturbations to the latest data of WMAP7. We compute as well the spectrum of the primordial gravitational waves as would be measured today. We show that the high frequencies region of the spectrum depends on the free parameter of the model and most importantly this region of the spectrum can be within the reach of future gravitational waves detectors.

In this paper, we compare seven popular dark energy models under the assumption of a flat universe by using the latest observational data of gravitationally-lensed image separations observed in the Cosmic Lens All-Sky Survey (CLASS), the PMN-NVSS Extragalactic Lens Survey (PANELS), the Sloan Digital Sky Survey (SDSS) and other surveys, which are (nearly) complete for the image separation range $0^{\prime \prime }.3\le \Delta \theta \le 7^{\prime \prime }$. We combine the 29 lens redshift data with the cosmic microwave background (CMB) observation from the Wilkinson Microwave Anisotropy Probe (WMAP7) results, the baryonic acoustic oscillation (BAO) observation from the spectroscopic Sloan Digital Sky Survey (SDSS) Data Release. The model comparison statistic, the Bayesian information criterion is also applied to assess the worth of the models. This statistic favors models that give a good fit with fewer parameters. Based on this analysis, we find that the simplest cosmological constant model that has only one free parameter is still preferred by the current data. For the other dynamical dark energy models, we find that some of them, such as the Ricci dark energy model, the Affine equation-of-state dark energy, and the generalized Chaplygin gas, can provide good fits to the current data. The Dvali-Gabadadze-Porrati model is the only one-parameter model that can give a rather good fit but also nest $\Lambda$ while the three-parameter model, namely, the interactive dark energy, is clearly disfavored by the data, as it is unable to provide a good fit.

We evaluate the three bulk viscosity coefficients ${\zeta }_1$, ${\zeta }_2$ and ${\zeta }_3$ in the color-flavor locked superfluid phase due to phonons and kaons, which are the lightest modes in that system. We first show that the computation is rather analogous to the computation of the same coefficients in superfluid ${}^4\mathrm{He}$, as due to phonons and rotons. For astrophysical applications, we also find the value of the viscosities when there is a periodic disturbance, and the viscosities also depend on the frequency of the disturbance. In a temperature regime that might be of astrophysical relevance, we find that the contributions of both the phonons and kaons should be considered, and that ${\zeta }_2$ is much less that the same coefficient in unpaired quark matter.