The measured forward-backward asymmetry in the $t\overline{t}$ production at the Tevatron might be explained by the additional exchange of a colored weak singlet scalar. Such state appears in some of the grand unified theories, and its interactions with the up-quarks are purely antisymmetric in flavor space. We systematically investigate the resulting impact on charm and top quark physics. The constraints on the relevant Yukawa couplings come from the experimentally measured observables related to $D^0\mathrm{\text{−}}{\overline{D}}^0$ oscillations, as well as dijet and single-top production measurements at the Tevatron. After fully constraining the relevant Yukawa couplings, we predict possible signatures of this model in rare top quark decays. In a class of grand unified models we demonstrate how the obtained information enables to constrain the Yukawa couplings of the up-quarks at very high energy scale.

We study further the soft-wall AdS/QCD model with a cubic potential for the bulk scalar. We analyze the spectra of pseudoscalar, scalar, vector, and axial-vector mesons. We also study the spin-$1/2$ nucleon spectrum and the pion-nucleon coupling. All of them have a good agreement with the experimental data.

We summarize exact solutions of closed superstrings in a constant magnetic field, from a viewpoint of the regularization criterion. Some models will be excluded according to this criterion.

A sum rule which relates a stress-energy tensor correlator to thermodynamic functions is examined within the context of a simple nonconformal gravity dual. Such a sum rule was previously derived using AdS/CFT for conformal $\mathcal{N}=4$ supersymmetric Yang-Mills theory, but we show that it does not generalize to the nonconformal theory under consideration. We provide a generalized sum rule and numerically verify its validity. A useful by-product of the calculation is the computation of the spectral density in a strongly coupled nonconformal theory. Qualitative features of the spectral densities and implications for lattice measurements of transport coefficients are discussed.

Holographic currents and their associated Ward identities are derived in the framework of gravity/gauge duality. Holographic improvements of the energy-momentum tensor and $R$-symmetry current which are consistent with the Ward identities are displayed. The effects of specific string loop corrections to the bulk action are included as four derivative effective Lagrangian terms and their contributions to the trace and $R$-symmetry anomalies of the boundary theory are determined. As an example, the construction is applied to the $\mathcal{N}=2$ conformal supergravity which is taken to be dual to a boundary $SU(N)\times SU(N)$, $\mathcal{N}=1$ superconformal field theory.

We use the entropy production variational method to associate a one-particle distribution function to the assumed known energy-momentum and entropy currents describing a relativistic conformal fluid. Assuming a simple form for the collision operator we find this one-particle distribution function explicitly, and show that this method of linking the hydro and kinetic descriptions is a nontrivial generalization of Grad’s ansatz. The resulting constitutive relations are the same as in the conformal dissipative type theories discussed by J. Peralta-Ramos and E. Calzetta [Phys. Rev. D 80, 126002 (2009)]. Our results may prove useful in the description of freeze-out in ultrarelativistic heavy-ion collisions.

We consider a $U(2)$ Yang-Mills theory on $\mathcal{M}\times S_F^2$, where $\mathcal{M}$ is an arbitrary noncommutative manifold, and $S_F^2$ is a fuzzy sphere spontaneously generated from a noncommutative $U(\mathcal{N})$ Yang-Mills theory on $\mathcal{M}$, coupled to a triplet of scalars in the adjoint of $U(\mathcal{N})$. Employing the $SU(2)$-equivariant gauge field constructed in [D. Harland and S. Kurkcuoglu, Nucl. Phys. B 821, 380 (2009).], we perform the dimensional reduction of the theory over the fuzzy sphere. The emergent model is a noncommutative $U(1)$ gauge theory coupled adjointly to a set of scalar fields. We study this model on the Groenewald-Moyal plane $\mathcal{M}={\mathbb{R}}_{\theta }^2$ and find that, in certain limits, it admits noncommutative, non-Bogomol’nyi-Prasad-Somerfield vortex as well as flux-tube (fluxon) solutions and discuss some of their properties.

In $D=2+1$ dimensions there are two dual descriptions of parity singlets of helicity $\pm 1$, namely, the self-dual model of first order (in derivatives) and the Maxwell-Chern-Simons theory of second order. Correspondingly, for helicity $\pm 2$ there are four models $S_{\mathrm{SD}\pm }^{(r)}$ describing parity singlets of helicities $\pm 2$. They are of first, second, third, and fourth order ($r=1$, 2, 3, 4), respectively. Here we show that the generalized soldering of the opposite helicity models $S_{\mathrm{SD}+}^{(4)}$ and $S_{\mathrm{SD}-}^{(4)}$ leads to the linearized form of the new massive gravity suggested by Bergshoeff, Hohm, and Townsend (BHT) similarly to the soldering of $S_{\mathrm{SD}+}^{(3)}$ and $S_{\mathrm{SD}-}^{(3)}$. We argue why in both cases we have the same result. We also find out a triple master action which interpolates between the three dual models: linearized BHT theory, $S_{\mathrm{SD}+}^{(3)}+S_{\mathrm{SD}-}^{(3)}$, and $S_{\mathrm{SD}+}^{(4)}+S_{\mathrm{SD}-}^{(4)}$. By comparing gauge invariant correlation functions we deduce dual maps between those models. In particular, we learn how to decompose the field of the linearized BHT theory in helicity eigenstates of the dual models up to gauge transformations.

A detailed derivation of the lattice Boltzmann scheme for relativistic fluids recently proposed in M. Mendoza, B. Boghosian, H. Herrmann, and S. Succi, Phys. Rev. Lett. 105, 014502 (2010) is presented. The method is numerically validated and applied to the case of two quite different relativistic fluid-dynamic problems, namely, shock-wave propagation in quark-gluon plasmas and the impact of a supernova blast wave on massive interstellar clouds. Close to second-order convergence with the grid resolution, as well as linear dependence of computational time on the number of grid points and time steps, are reported.

Through Alday-Gaiotto-Tachikawa conjecture, we show how triality observed in $\mathcal{N}=2$ $SU(2)$ $N_f=4$ QCD can be interpreted geometrically as the interplay among six of Kummer’s 24 solutions belonging to one fixed Riemann scheme in the context of hypergeometric differential equations.

The Lichnerowicz and Israel theorems are extended to higher order theories of gravity. In particular it is shown that Schwarzschild is the unique spherically symmetric, static, asymptotically flat, black-hole solution, provided the spatial curvature is less than the quantum gravity scale outside the horizon. It is then shown that in the presence of matter (satisfying certain positivity requirements), the only static and asymptotically flat solutions of general relativity that are also solutions of higher order gravity are the vacuum solutions.

Rapidly rotating Myers-Perry black holes in $d\ge 6$ dimensions were conjectured to be unstable by Emparan and Myers. In a previous publication, we found numerically the onset of the axisymmetric ultraspinning instability in the singly spinning Myers-Perry black hole in $d=7$, 8, 9. This threshold also signals a bifurcation to new branches of axisymmetric solutions with pinched horizons that are conjectured to connect to the black ring, black Saturn and other families in the phase diagram of stationary solutions. We firmly establish that this instability is also present in $d=6$ and in $d=10$, 11. The boundary conditions of the perturbations are discussed in detail for the first time, and we prove that they preserve the angular velocity and temperature of the original Myers-Perry black hole. This property is fundamental to establishing a thermodynamic necessary condition for the existence of this instability in general rotating backgrounds. We also prove a previous claim that the ultraspinning modes cannot be pure gauge modes. Finally we find new ultraspinning Gregory-Laflamme instabilities of rotating black strings and branes that appear exactly at the critical rotation predicted by the aforementioned thermodynamic criterium. The latter is a refinement of the Gubser-Mitra conjecture.

Spherically symmetric shock waves are shown to exist in Lovelock gravity. They amount to a change of branch of the spherically symmetric solutions across a null hypersurface. The implications of their existence for the status of Birkhoff’s theorem in the theory is discussed.

We study the observational constraints on the exponential gravity model of $f(R)=-\beta R_s(1-e^{-R/R_s})$. We use the latest observational data including Supernova Cosmology Project Union2 compilation, Two-Degree Field Galaxy Redshift Survey, Sloan Digital Sky Survey Data Release 7, and Seven-Year Wilkinson Microwave Anisotropy Probe in our analysis. From these observations, we obtain a lower bound on the model parameter $\beta$ at 1.27 (95% C.L.) but no appreciable upper bound. The constraint on the present matter density parameter is $0.245<{\Omega }_m^0<0.311$ (95% C.L.). We also find out the best-fit value of model parameters on several cases.

The persistent discrepancy between observations of ${}^7\mathrm{Li}$ with putative primordial origin and its abundance prediction in big bang nucleosynthesis has become a challenge for the standard cosmological and astrophysical picture. We point out that the decay of GeV-scale metastable particles $X$ may significantly reduce the big bang nucleosynthesis value down to a level at which it is reconciled with observations. The most efficient reduction occurs when the decay happens to charged pions and kaons, followed by their charge-exchange reactions with protons. Similarly, if $X$ decays to muons, secondary electron antineutrinos produce a similar effect. We consider the viability of these mechanisms in different classes of new GeV-scale sectors, and find that several minimal extensions of the standard model with metastable vectors and/or scalar particles are capable of solving the cosmological lithium problem. Such light states can be a key to the explanation of recent cosmic ray anomalies and can be searched for in a variety of high-intensity medium-energy experiments.

We investigate the observational constraints on the oscillating scalar field model using data from type Ia supernovae, cosmic microwave background anisotropies, and baryon acoustic oscillations. According to a Fourier analysis, the galaxy number count $N$ from redshift $z$ data indicates that galaxies have preferred periodic redshift spacings. We fix the mass of the scalar field as $m_{\varphi }=3.2\times {10}^{-31}h\mathrm{eV}$ such that the scalar field model can account for the redshift spacings, and we constrain the other basic parameters by comparing the model with accurate observational data. We obtain the following constraints: ${\Omega }_{m,0}=0.28\pm 0.03$ (95% C.L.), ${\Omega }_{\varphi ,0}<0.035$ (95% C.L.), and $\xi >-158$ (95% C.L.) (in the range $\xi \le 0$). The best fit values of the energy density parameter of the scalar field and the coupling constant are ${\Omega }_{\varphi ,0}=0.01$ and $\xi =-25$, respectively. The value of ${\Omega }_{\varphi ,0}$ is close to but not equal to 0. Hence, in the scalar field model, the amplitude of the galaxy number count cannot be large. However, because the best fit values of ${\Omega }_{\varphi ,0}$ and $\xi$ are not 0, the scalar field model has the possibility of accounting for the periodic structure in the $N\mathrm{\text{−}}z$ relation of galaxies. The variation of the effective gravitational constant in the scalar field model is not inconsistent with the bound from observation.

Nonlinear CMB temperature anisotropies up to the third order on large scales are calculated. On large scales and in the Sachs-Wolfe limit, we give the explicit expression for the observed temperature anisotropy in terms of the primordial curvature perturbation up to the third order. We derived the final bispectrum and trispectrum of anisotropies and the corresponding nonlinear parameters, in which the contributions to the observed non-Gaussianity from primordial perturbations and from the nonlinear mapping from primordial curvature perturbation to the temperature anisotropy are transparently separated.