We perform a perturbative calculation of the influence of dynamical highly improved staggered quark fermions on the perturbative improvement of the gluonic action in the same way as we have previously done for asqtad fermions. We find the fermionic contributions to the radiative corrections in the Lüscher-Weisz gauge action to be somewhat larger for highly improved staggered quark fermions than for asqtad. Using one-loop perturbation theory as a test, we estimate that omission of the fermion-induced radiative corrections in dynamical asqtad simulations will give a measurable effect. The one-loop result gives a systematic shift of about $-0.6\%$ in ${\widehat{r}}_1$ on the coarsest asqtad improved staggered ensembles. This is the correct sign and magnitude to explain the scaling violations seen in ${\Phi }_B=f_B\sqrt{M_B}$ on dynamical lattice ensembles.

The weak decays of $B\to K_0^{*}(1430)l^{+}{l}^{-}$ ($l=\mu$, $\tau$) are investigated in minimal supersymmetric standard model (MSSM) and also in supersymmetric (SUSY) SO(10) grand unified theory (GUT) models. Neutral Higgs bosons are the point of main focus in MSSM because they make quite a large contribution in exclusive $B\to X_s{l}^{+}{l}^{-}$ decays at large $\tan \beta$ regions of parameter space of SUSY models, as part of SUSY contributions is proportional to ${tan}^3\beta$. The analysis of decay rate, forward-backward asymmetries and lepton polarization asymmetries in $B\to K_0^{*}(1430)l^{+}{l}^{-}$ show that the values of these physical observables are greatly modified by the effects of neutral Higgs bosons. In SUSY SO(10) grand unified model, the new physics contribution comes from the operators which are induced by the neutral Higgs boson penguins and also from the operators with chirality opposite to that of the corresponding standard model operators. SUSY SO(10) effects show up only in the decay $B\to K_0^{*}{\mu }^{+}{\mu }^{-}$ where the transverse lepton polarization asymmetries deviate significantly from the SM value while the effects in the decay rate, forward-backward asymmetries, the longitudinal and normal lepton polarization asymmetries are very mild. The transverse lepton polarization asymmetry is almost zero in SM and in MSSM model, whereas it can reach to $-0.3$ in SUSY SO(10) GUT model which could be seen at the future colliders; hence this asymmetry observable can be used to discriminate between different SUSY models.

All quark mass matrices with texture zeroes obtained through weak basis transformations are confronted with the experimental data. The reconstruction of the quark mass matrices $M_u$ and $M_d$ at the electroweak scale is performed in a weak basis where the matrices are Hermitian and have a maximum of three vanishing elements. The same procedure is also accomplished for the Yukawa coupling matrices at the grand unification scale in the context of the standard model and its minimal supersymmetric extension as well as of the two Higgs doublet model. The analysis of all viable power structures on the quark Yukawa coupling matrices that could naturally appear from a Froggatt-Nielsen mechanism is also presented.

We study the impact of very light sterile neutrinos ($\Delta m_{\mathrm{new}}^2\in [1,10]\times {10}^{-2}{\mathrm{eV}}^2$, ${sin}^{2}2{\theta }_{\mathrm{new}}<{10}^{-1}$) on analyses of upcoming ${\theta }_{13}$-driven reactor antineutrino experiments like Double CHOOZ and Daya Bay. Oscillations driven by these values of $\Delta m_{\mathrm{new}}^2$ affect data in the near and far detectors differently and hence potentially modify the capability of these experimental setups to constrain and measure ${sin}^{2}2{\theta }_{13}$. We find that the hypothesis ${\theta }_{\mathrm{new}}\ne 0$ negatively impacts one’s ability to place an upper bound on ${sin}^{2}2{\theta }_{13}$ in the advent of a no-oscillation signal or to measure ${sin}^{2}2{\theta }_{13}$ if a ${\theta }_{13}$-driven signal is observed. The impact of sterile neutrino effects, however, depends dramatically on one’s ability to measure the recoil positron energy spectrum. If ${sin}^{2}2{\theta }_{\mathrm{new}}\gtrsim {10}^{-2}$, upcoming ${\theta }_{13}$-driven reactor antineutrino experiments should be able to measure ${sin}^{2}2{\theta }_{\mathrm{new}}$ and $\Delta m_{\mathrm{new}}^2$, along with ${sin}^{2}2{\theta }_{13}$, as long as one is sensitive to distortions in the recoil positron energy spectrum in the near (and far) detectors.

We discuss a constraint on the scale ${\Lambda }_{\mathrm{NC}}$ of noncommutative (NC) gauge field theory arising from consideration of the big bang nucleosynthesis of light elements. The propagation of neutrinos in the NC background described by an antisymmetric tensor ${\theta }^{\mu \nu }$ does result in a tree-level vectorlike coupling to photons in a generation-independent manner, raising thus a possibility to have an appreciable contribution of three light right-handed (RH) fields to the energy density of the Universe at nucleosynthesis time. Considering elastic scattering processes of the RH neutrinos off charged plasma constituents at a given cosmological epoch, we obtain for a conservative limit on an effective number of additional doublet neutrinos $\Delta N_{\nu }=1$, a bound ${\Lambda }_{\mathrm{NC}}\gtrsim 3\mathrm{TeV}$. With a more stringent requirement, $\Delta N_{\nu }\lesssim 0.2$, the bound is considerably improved, ${\Lambda }_{\mathrm{NC}}\gtrsim {10}^3\mathrm{TeV}$. For our bounds the $\theta$ expansion of the NC action stays always meaningful, since the decoupling temperature of the RH species is perseveringly much less than the inferred bound for the scale of noncommutativity.

We find a class of solutions to cosmological Einstein equations that generalizes the four dimensional cylindrically symmetric spacetimes to higher dimensions. The AdS soliton is a special member of this class with a unique singularity structure.

Using the anti-de Sitter/conformal field theory correspondence, we calculate a fermionic spectral function in a $2+1$ dimensional nonrelativistic quantum field theory which is dual to a gravitational theory in the ${\mathrm{AdS}}_4$ background with a charged black hole. The spectral function shows no quasiparticle peak but the Fermi surface is still well-defined. Interestingly, all momentum points inside the Fermi surface are critical and the gapless modes are defined in a critical Fermi ball in the momentum space.

We investigate the possibility of using icosahedral symmetry as a family symmetry group in the lepton sector. The rotational icosahedral group, which is isomorphic to $A_5$, the alternating group of five elements, provides a natural context in which to explore (among other possibilities) the intriguing hypothesis that the solar neutrino mixing angle is governed by the golden ratio, $\varphi =(1+\sqrt{5})/2$. We present a basic toolbox for model building using icosahedral symmetry, including explicit representation matrices and tensor product rules. As a simple application, we construct a minimal model at tree level in which the solar angle is related to the golden ratio, the atmospheric angle is maximal, and the reactor angle vanishes to leading order. The approach provides a rich setting in which to investigate the flavor puzzle of the standard model.

We obtain static self-gravitating solitonic 3-brane solutions in the Einstein-Skyrme model in 7D. These solitons correspond to a smooth version of the previously discussed cosmic $p$-brane solutions. We show how the energy-momentum tensor of the Skyrme field is able to smooth out the singularities found in the thin wall approximation and falls fast enough with the distance from the core of the object so that it asymptotically approaches the flat cosmic $p$-brane metric.

We study thermalization by applying gradient expansion to the Kadanoff-Baym equations of the two-particle-irreducible effective action to two-loop in a theory with Dirac fermions coupled to scalars. In addition to those chemical potentials that equilibrate in the on-shell limit, we identify modes that are conserved in this approximation, but which relax when off-shell effects are taken into account. This implies that chemical equilibration does not require higher loop contributions to the effective action and is compatible with the gradient expansion. We explicitly calculate the damping time scales of both, on- and off-shell, chemical equilibration rates. It is shown that off-shell equilibration is suppressed by the thermal width of the particles in the plasma, which explains the separation of on- and off-shell chemical equilibration time scales.

Popular approaches to quantum gravity describe black hole microstates differently and apply different statistics to count them. Since the relationship between the approaches is not clear, this obscures the role of statistics in calculating the black hole entropy. We address this issue by discussing the entropy of eternal AdS black holes in dimension four and above within the context of a midisuperspace model. We determine the black hole eigenstates and find that they describe the quantization in half integer units of a certain function of the Arnowitt-Deser-Misner (ADM) mass and the cosmological constant. In the limit of a vanishing cosmological constant (the Schwarzschild limit) the quantized function becomes the horizon area and in the limit of a large cosmological constant it approaches the ADM mass of the black holes. We show that in the Schwarzschild limit the area quatization leads to the Bekenstein-Hawking entropy if Boltzmann statistics are employed. In the limit of a large cosmological constant the Bekenstein-Hawking entropy can be recovered only via Bose statistics. The two limits are separated by a first order phase transition, which seems to suggest a shift from “particlelike” degrees of freedom at large cosmological constant to geometric degrees of freedom as the cosmological constant approaches zero.

Modifications to the gravitational potential affect the nonlinear gravitational evolution of large scale structures in the Universe. To illustrate some generic features of such changes, we study the evolution of spherically symmetric perturbations when the modification is of Yukawa type; this is nontrivial, because we should not and do not assume that Birkhoff’s theorem applies. We then show how to estimate the abundance of virialized objects in such models. Comparison with numerical simulations shows reasonable agreement: When normalized to have the same fluctuations at early times, weaker large scale gravity produces fewer massive halos. However, the opposite can be true for models that are normalized to have the same linear theory power spectrum today, so the abundance of rich clusters potentially places interesting constraints on such models. Our analysis also indicates that the formation histories and abundances of sufficiently low mass objects are unchanged from standard gravity. This explains why simulations have found that the nonlinear power spectrum at large $k$ is unaffected by such modifications to the gravitational potential. In addition, the most massive objects in models with normalized cosmic microwave background and weaker gravity are expected to be similar to the high-redshift progenitors of the most massive objects in models with stronger gravity. Thus, the difference between the cluster and field galaxy populations is expected to be larger in models with stronger large scale gravity.

In this paper we develop a technique for determining the algebraic classification of a numerically generated spacetime, possibly resulting from a generic black-hole-binary merger, using the Newman-Penrose Weyl scalars. We demonstrate these techniques for a test case involving a close binary with arbitrarily oriented spins and unequal masses. We find that, postmerger, the spacetime quickly approaches Petrov type II, and only approaches type D on much longer time scales. These techniques, in combination with techniques for evaluating acceleration and Newman-Unti-Tamburino parameters, allow us to begin to explore the validity of the “no-hair theorem” for generic merging-black-hole spacetimes.

We propose a simple model of supersymmetric dark matter that can explain recent results from PAMELA and ATIC experiments. It is based on a $U(1{)}_{B-L}$ extension of the minimal supersymmetric standard model. The dark matter particle is a linear combination of the $U(1{)}_{B-L}$ gaugino and Higgsino partners of Higgs fields that break the $B-L$ around 1 TeV. The dominant mode of dark matter annihilation is to the lightest of the new Higgs fields, which has a mass in the GeV range, and its subsequent decay mainly produces taus or muons by the virtue of $B-L$ charges. This light Higgs also results in Sommerfeld enhancement of the dark matter annihilation cross section, which can be $\gtrsim {10}^3$. For a dark matter mass in the 1–2 TeV range, the model provides a good fit to the PAMELA data and a reasonable fit to the ATIC data. We also briefly discuss the prospects of this model for direct detection experiments and the LHC.

In this report we describe both $I=2$ and $I=0$ $\pi \pi$ scattering for twisted mass lattice QCD utilizing twisted mass chiral perturbation theory at next-to-leading order. Focusing on the lattice spacing ($b$) corrections, we demonstrate that in the exotic $I=2$, $I_3=\pm 2$ channels (${\pi }^{\pm }{\pi }^{\pm }$), the leading scaling violations of $\pi \pi$ scattering at maximal twist begin at $\mathcal{O}(m_{\pi }^2{b}^2)$. This is not the case in any other isospin channel, for which the scaling violations at maximal twist begin at $\mathcal{O}(b^2)$. Furthermore, we demonstrate the existence of a mixing between the $I=2$, $I_3=0$ and $I=0$ scattering channels due to the breaking of isospin symmetry by the twisted mass term. The mixing term, although formally next-to-leading order, is relatively large, thus necessitating the use of a coupled channel analysis. We argue that this mixing likely renders the computation of the $I=0$ channel impractical with twisted mass lattice QCD.

The mixing between nonstrange and strange quark wave functions in the $\omega$ and $\varphi$ mesons leads to a small predicted branching ratio $\mathcal{B}(D_s^{+}\to \omega e^{+}{\nu }_e)=\mathcal{O}({10}^{-4})(\delta /3.34°{)}^2$, where $\delta$ is the mixing angle. The value $\delta =-3.34°$ is obtained in a mass-independent analysis, while a mass-dependent analysis gives $\delta =-0.45°$ at $m(\omega )$ and $-4.64°$ at $m(\varphi )$. Measurement of this branching ratio thus can tell whether the decay is dominated by $\varphi -\omega$ mixing, or additional nonperturbative processes commonly known as “weak annihilation” (WA) contribute. The role of WA in the decay $D_s^{+}\to \omega {\pi }^{+}$ and its possible use in estimating WA effects in $D_s^{+}\to \omega e^{+}{\nu }_e$ are also discussed. Assuming that the dynamics of WA in $D_s^{+}\to \omega {\pi }^{+}$ is similar in $D_s^{+}\to \omega e^{+}{\nu }_e$ we estimate $\mathcal{B}(D_s^{+}\to \omega e^{+}{\nu }_e)=(1.3\pm 0.5)\times {10}^{-3}$.

An analytical expression for the spin-averaged amplitude squared of the rare muon decay ${\mu }^{+}\to e^{+}{e}^{-}{e}^{+}{\nu }_e{\overline{\nu }}_{\mu }$ is calculated. Monte Carlo phase space simulation using the analytical expression for the amplitude has been used to get various differential distributions of charged leptons. The approximate analytical expression for the total energy spectrum of charged leptons near the end point is presented. The dependence of the branching ratio on cuts in the total energy of charged leptons is studied taking into account an experimental energy resolution. It is shown that the measured branching ratio is very sensitive to the energy resolution.

We show that the minimal set of necessary ingredients to construct explicit, four-dimensional de Sitter solutions from IIA string theory at tree level are O6-planes, nonzero Romans mass parameter, form fluxes, and negative internal curvature. To illustrate our general results, we construct such minimal simple de Sitter solutions from an orientifold compactification of compact hyperbolic spaces. In this case there are only two moduli and we demonstrate that they are stabilized to a sufficiently weakly coupled and large volume regime. We also discuss generalizations of the scenario to more general metric flux constructions.

We study the operator product expansion in the ${\mathrm{AdS}}_3$ Wess-Zumino-Novikov-Witten (WZNW) model. The operator-product expansion of primary fields and their spectral flow images is computed from the analytic continuation of the expressions in the ${\mathrm{H}}_3^{+}$ WZNW model, adding spectral flow. We argue that the symmetries of the affine algebra require a truncation which establishes the closure of the fusion rules on the Hilbert space of the theory. Although the physical mechanism determining the decoupling is not completely understood, we present several consistency checks on the results. A preliminary analysis of factorization allows to obtain some properties of four-point functions involving fields in generic sectors of the theory, to verify that they agree with the spectral flow selection rules and to show that the truncation must be realized in physical amplitudes for consistency.

We studied the Adler-Bardeen-Bell-Jackiw anomaly in the context of a finite chiral quark model known as the spectral quark model. Within this model, we obtain the general nonlocal form of the axial vertex compatible with a nonvanishing axial coupling, in the chiral limit. The triangle anomaly is computed and we show that the obtained dependence of the axial vertex with the spectral mass is necessary to ensure both finiteness and the correct violation of the chiral Ward-Takahashi identity.