A model of neutrino oscillations is presented that has only 3 degrees of freedom and appears compatible with existing data. The model is a subset of the renormalizable sector of the Standard-Model Extension (SME), and it offers a candidate alternative to the standard three-neutrino massive model. All classes of neutrino data are described, including solar, reactor, atmospheric, and LSND oscillations. The disappearance of solar neutrinos is obtained without matter-enhanced oscillations. Quantitative predictions are offered for the ongoing MiniBooNE experiment and for the future experiments OscSNS, NOvA, and T2K.

We consider $1+4$ dimensional black-string solutions which are invariant under translation along the fifth direction. The solutions are characterized by the two parameters, mass and tension, of the source. The Gregory-Laflamme solution is shown to be characterized by the tension whose magnitude is one half of the mass per unit length of the source. A general class of black-string solutions with arbitrary tension is presented and the spacetime properties of the solutions are discussed.

We consider the role of supersymmetric flat directions in reheating the Universe after inflation. One or more flat directions can develop large vevs during inflation, which can potentially affect reheating by slowing down scattering processes among inflaton decay products or by coming to dominate the energy density of the Universe. Both effects occur only if flat directions are sufficiently long-lived. The computation of their perturbative decay rate, and a simple estimate of their nonperturbative decay have led to the conclusion that this is indeed the case. In contrast, we show that flat directions can decay quickly through nonperturbative channels in realistic models. The mass matrix for minimal supersymmetric standard model (MSSM) excitations around flat directions has nondiagonal entries, which vary with the phase of the (complex) flat directions. The quasiperiodic motion of the flat directions results in a strong parametric resonance, leading to the rapid depletion of the flat direction within its first few rotations. This may preclude any significant role for the flat directions in reheating the Universe after inflation in models in which the inflaton decays perturbatively.

A relativistic theory of gravity has recently been proposed by Bekenstein, where gravity is mediated by a tensor, a vector, and a scalar field, thus called TeVeS. The theory aims at modifying gravity in such a way as to reproduce Milgrom’s modified Newtonian dynamics (MOND) in the weak field, nonrelativistic limit, which provides a framework to solve the missing mass problem in galaxies without invoking dark matter. In this paper I apply a covariant approach to formulate the cosmological equations for this theory, for both the background and linear perturbations. I derive the necessary perturbed equations for scalar, vector, and tensor modes without adhering to a particular gauge. Special gauges are considered in the appendixes.

We study collider signals for the noncommutative extension of the standard model using the Seiberg-Witten maps for $\mathrm{SU}(3{)}_C\otimes \mathrm{SU}(2{)}_L\otimes \mathrm{U}(1{)}_Y$ to first order in the noncommutativity parameters ${\theta }_{\mu \nu }$. In particular, we investigate the sensitivity of $Z\gamma$-production at the Tevatron and the LHC to the components of ${\theta }_{\mu \nu }$. We discuss the range of validity of this approximation and estimate exclusion limits from a Monte Carlo simulation.

Using previously formulated sum rules in the heavy quark limit of QCD, we demonstrate that if the slope ${\rho }^2=-{\xi }^{\prime }(1)$ of the Isgur-Wise (IW) function $\xi (w)$ attains its lower bound $\frac{3}{4}$, then all the derivatives $(-1{)}^L{\xi }^{(L)}(1)$ attain their lower bounds $\frac{(2L+1)!!}{2^{2L}}$, obtained by Le Yaouanc et al. This implies that the IW function is completely determined, given by the function $\xi (w)=(\frac{2}{w+1}{)}^{3/2}$. Since the so-called BPS condition proposed by Uraltsev implies ${\rho }^2=\frac{3}{4}$, it implies also that the IW function is given by the preceding expression.

We measure the dimuon charge asymmetry $A$ in $p\overline{p}$ collisions at a center of mass energy $\sqrt{s}=1960\mathrm{GeV}$. The data was recorded with the D0 detector and corresponds to an integrated luminosity of approximately $1.0{\mathrm{fb}}^{-1}$. Assuming that the asymmetry $A$ is due to asymmetric $B^0\leftrightarrow {\overline{B}}^0$ mixing and decay, we extract the $CP$-violation parameter of $B^0$ mixing and decay: $\frac{\Re ({ϵ}_{B^0})}{1+|{ϵ}_{B^0}{|}^2}=\frac{A_{B^0}}{4}=-0.0023\pm 0.0011(\mathrm{stat})\pm 0.0008(\mathrm{syst}).$$A_{B^0}$ is the dimuon charge asymmetry from decays of $B^0{\overline{B}}^0$ pairs. The general case, with $CP$ violation in both $B^0$ and $B_s^0$ systems, is also considered. Finally we obtain the forward-backward asymmetry that quantifies the tendency of ${\mu }^{+}$ to go in the proton direction and ${\mu }^{-}$ to go in the antiproton direction. The results are consistent with the standard model and constrain new physics.

We solve the gap equation for color-superconducting quark matter in the 2SC phase, including both the energy and the momentum dependence of the gap, $\varphi =\varphi (k_0,\mathbf{k})$. For that purpose a complex Ansatz for $\varphi$ is made. The calculations are performed within an effective theory for cold and dense quark matter. The solution of the complex gap equation is valid to subleading order in the strong-coupling constant $g$ and in the limit of zero temperature. We find that, for momenta sufficiently close to the Fermi surface and for small energies, the dominant contribution to the imaginary part of $\varphi$ arises from Landau-damped magnetic gluons. Further away from the Fermi surface and for larger energies the other gluon sectors have to be included into $\mathrm{Im}\varphi$. We confirm that $\mathrm{Im}\varphi$ contributes a correction of order $g$ to the prefactor of $\varphi$ for on-shell quasiquarks sufficiently close to the Fermi surface, whereas further away from the Fermi surface $\mathrm{Im}\varphi$ and $\mathrm{Re}\varphi$ are of the same order. Finally, we discuss the relevance of $\mathrm{Im}\varphi$ for the damping of quasiquark excitations.

We pursue the study of $SU(2)$ Euclidean Yang-Mills theory in the maximal Abelian gauge by taking into account the effects of the Gribov horizon. The Gribov approximation, previously introduced in [M. A. L. Capri, V. E. R. Lemes, R. F. Sobreiro, S. P. Sorella, and R. Thibes, Phys. Rev. D 72, 085021 (2005).], is improved through the introduction of the horizon function, which is constructed under the requirements of localizability and renormalizability. By following Zwanziger’s treatment of the horizon function in the Landau gauge, we prove that, when cast in local form, the horizon term of the maximal Abelian gauge leads to a quantized theory which enjoys multiplicative renormalizability, a feature which is established to all orders by means of the algebraic renormalization. Furthermore, it turns out that the horizon term is compatible with the local residual $U(1)$ Ward identity, typical of the maximal Abelian gauge, which is easily derived. As a consequence, the nonrenormalization theorem, $Z_g{Z}_A^{1/2}=1$, relating the renormalization factors of the gauge coupling constant $Z_g$ and of the diagonal gluon field $Z_A$, still holds in the presence of the Gribov horizon. Finally, we notice that a generalized dimension two gluon operator can be also introduced. It is BRST invariant on-shell, a property which ensures its multiplicative renormalizability. Its anomalous dimension is not an independent parameter of the theory, being obtained from the renormalization factors of the gauge coupling constant and of the diagonal antighost field.

Spacetimes with horizons show a resemblance to thermodynamic systems and one can associate the notions of temperature and entropy with them. In the case of Einstein-Hilbert gravity, it is possible to interpret Einstein’s equations as the thermodynamic identity $TdS=dE+PdV$ for a spherically symmetric spacetime and thus provide a thermodynamic route to understand the dynamics of gravity. We study this approach further and show that the field equations for the Lanczos-Lovelock action in a spherically symmetric spacetime can also be expressed as $TdS=dE+PdV$ with $S$ and $E$ given by expressions previously derived in the literature by other approaches. The Lanczos-Lovelock Lagrangians are of the form $\mathcal{L}=Q_a{}^{bcd}R^a{}_{bcd}$ with ${\nabla }_{b}Q_a{}^{bcd}=0$. In such models, the expansion of $Q_a{}^{bcd}$ in terms of the derivatives of the metric tensor determines the structure of the theory and higher order terms can be interpreted as quantum corrections to Einstein gravity. Our result indicates a deep connection between the thermodynamics of horizons and the allowed quantum corrections to standard Einstein gravity, and shows that the relation $TdS=dE+PdV$ has a greater domain of validity than Einstein’s field equations.

We construct a class of charged rotating solutions in ($n+1$)-dimensional Maxwell-Brans-Dicke theory with flat horizon in the presence of a quadratic potential and investigate their properties. These solutions are neither asymptotically flat nor (anti)-de Sitter. We find that these solutions can present black brane, with inner and outer event horizons, an extreme black brane or a naked singularity provided the parameters of the solutions are chosen suitably. We compute the finite Euclidean action through the use of counterterm method, and obtain the conserved and thermodynamic quantities by using the relation between the action and free energy in grand-canonical ensemble. We find that these quantities satisfy the first law of thermodynamics, and the entropy does not follow the area law.

A commonly used perturbative method for computing large-scale clustering of tracers of mass density, like galaxies, is to model the tracer density field as a Taylor series in the local smoothed mass density fluctuations, possibly adding a stochastic component. I suggest a set of parameter redefinitions, eliminating problematic perturbative correction terms, that should represent a modest improvement, at least, to this method. As presented here, my method can be used to compute the power spectrum and bispectrum to 4th order in initial density perturbations, and higher order extensions should be straightforward. While the model is technically unchanged at this order, just reparametrized, the renormalized model is more elegant, and should have better convergence behavior, for three reasons: First, in the usual approach the effects of beyond-linear-order bias parameters can be seen at asymptotically large scales, while after renormalization the linear model is preserved in the large-scale limit, i.e., the effects of higher order bias parameters are restricted to relatively high $k$. Second, while the standard approach includes smoothing to suppress large perturbative correction terms, resulting in dependence on the arbitrary cutoff scale, no cutoff-sensitive terms appear explicitly after my redefinitions (and, relatedly, my correction terms are less sensitive to high-$k$, nonlinear, power). Third, the 3rd order bias parameter disappears entirely, so my model has one fewer free parameter than usual (this parameter was redundant at the order considered). This model predicts no significant modification of the baryonic acoustic oscillation (BAO) signal, in real space, supporting the robustness of BAO as a probe of dark energy, and providing a complete perturbative description over the relevant range of scales.

The thermal equilibrium of string gas is necessary to activate the Brandenberger-Vafa mechanism, which makes our observed 4-dimensional universe enlarge. Nevertheless, the thermal equilibrium is not realized in the original setup, a problem that remains as a critical defect. We study thermal equilibrium in the Hagedorn universe, and explore possibilities for avoiding the issue aforementioned flaw. We employ a minimal modification of the original setup, introducing a dilaton potential. Two types of potential are investigated: exponential and double-well potentials. For the first type, the basic evolutions of universe and dilaton are such that both the radius of the universe and the dilaton asymptotically grow in over a short time, or that the radius converges to a constant value while the dilaton rolls down toward the weak coupling limit. For the second type, in addition to the above solutions, there is another solution in which the dilaton is stabilized at a minimum of potential and the radius grows in proportion to $t$. Thermal equilibrium is realized for both cases during the initial phase. These simple setups provide possible resolutions of the difficulty.

We consider the weak lensing effect induced by linear cosmological perturbations on the cosmic microwave background (CMB) polarization anisotropies. We find that the amplitude of the lensing peak in the BB mode power spectrum is a faithful tracer of the dark energy dynamics at the onset of cosmic acceleration. This is due to two reasons. First, the lensing power is nonzero only at intermediate redshifts between the observer and the source, keeping record of the linear perturbation growth rate at the corresponding epoch. Second, the BB lensing signal is expected to dominate over the other sources. The lensing distortion on the TT and EE spectra do exhibit a similar dependence on the dark energy dynamics, although those are dominated by primary anisotropies. We investigate and quantify the effect by means of exact tracking quintessence models, as well as parameterizing the dark energy equation of state in terms of the present value ($w_0$) and its asymptotic value in the past ($w_{\infty }$); in the interval allowed by the present constraints on dark energy, the variation of $w_{\infty }$ induces a significant change in the BB mode lensing amplitude. A Fisher matrix analysis, under conservative assumptions concerning the increase of the sample variance due to the lensing non-Gaussian statistics, shows that a precision of order 10% on both $w_0$ and $w_{\infty }$ is achievable by the future experiments probing a large sky area with angular resolution and sensitivity appropriate to detect the lensing effect on the CMB angular power spectrum; the forecast precision reaches a few percent for highly dynamic models whose dark energy abundance at the epoch when lensing is most effective is sensibly larger than the present one, i.e. for $w_{\infty }\gtrsim -0.5$. These results show that the CMB can probe the differential redshift behavior of the dark energy equation of state, beyond its average.

Charged particles ($X$) decaying after primordial nucleosynthesis are constrained by the requirement that their decay products should not change the light element abundances drastically. If the decaying particle is negatively charged ($X^{-}$) then it will bind to the nuclei. We consider the effects of the decay of $X$ when bound to Helium-4 and show that this will modify the Lithium abundances.

We use the $\delta N$ formalism to investigate the non-Gaussianity of the primordial curvature perturbation in the curvaton scenario for the origin of structure. We numerically calculate the full probability distribution function allowing for the noninstantaneous decay of the curvaton and compare this with analytic results derived in the sudden-decay approximation. We also present results for the leading-order contribution to the primordial bispectrum and trispectrum. In the sudden-decay approximation we derive a fully nonlinear expression relating the primordial perturbation to the initial curvaton perturbation. As an example of how non-Gaussianity provides additional constraints on model parameters, we show how the primordial bispectrum on cosmic microwave background scales can be used to constrain variance on much smaller scales in the curvaton field. Our analytical and numerical results allow for multiple tests of primordial non-Gaussianity, and thus they can offer consistency tests of the curvaton scenario.

In a variety of supersymmetric extensions of the standard model, the scalar partners of the quarks and leptons are predicted to be very heavy and beyond the reach of next-generation colliders. For instance, the realization of electroweak baryogenesis in supersymmetry requires new sources of $CP$ violation, which can only be naturally accommodated with electric dipole moment constraints if the first- and second-generation scalar fermions are beyond the TeV scale. Also, in focus-point supersymmetry and split supersymmetry the scalar fermions are very heavy. In this work, the phenomenology of scenarios with electroweak baryogenesis and in the focus-point region at the CERN LHC and ILC is studied, which becomes challenging due to the presence of heavy scalar fermions. Implications for the analysis of baryogenesis and dark matter are deduced. It is found that precision measurements of superpartner properties allow an accurate determination of the dark matter relic density in both scenarios, while important but only incomplete information about the baryogenesis mechanism can be obtained.

We propose a means to discriminate between the two basic variants of Little Higgs models, the Product Group and Simple Group models, at the next generation of colliders. It relies on a special coupling of light pseudoscalar particles present in Little Higgs models, the pseudoaxions, to the $Z$ and the Higgs boson, which is present only in Simple Group models. We discuss the collider phenomenology of the pseudoaxion in the presence of such a coupling at the LHC, where resonant production and decay of either the Higgs or the pseudoaxion induced by that coupling can be observed for much of parameter space. The full allowed range of parameters, including regions where the observability is limited at the LHC, is covered by a future ILC, where double scalar production would be a golden channel to look for.

We study a $4+1$ dimensional pure Abelian Gauge model on the lattice with two anisotropic couplings independent of each other and of the coordinates. A first exploration of the phase diagram using mean field approximation and monte carlo techniques has demonstrated the existence of a new phase, the so called Layer phase, in which the forces in the 4-D subspace are Coulomb-like while in the transverse direction (fifth dimension) the force is confining. This allows the possibility of a gauge field localization scheme. In this work the use of bigger lattice volumes and higher statistics confirms the existence of the Layer phase and furthermore clarifies the issue of the phase transitions’ order. We show that the Layer phase is separated from the strongly coupled phase by a weak first order phase transition. Also we provide evidence that the Layer phase is separated by the five-dimensional Coulomb phase with a second order phase transition and we give a first estimation of the critical exponents.

We consider the recent RHIC data on the transverse single spin asymmetry (SSA) $A_N$, measured in $p^{\uparrow }p\to {\pi }^{0}X$ processes at midrapidity by the PHENIX Collaboration. The measurement is consistent with a vanishing SSA. We analyze this experimental information within a hard scattering approach based on a generalized QCD factorization scheme, with unintegrated, transverse momentum dependent (TMD), parton distribution and fragmentation functions. It turns out that, in the kinematical region of the data, only the gluon Sivers effect could give a large contribution to $A_N$; its vanishing value is thus an indication about the possible size of the gluon Sivers function (GSF). Approximate upper limits on its magnitude are derived. Additional constraints obtained combining available parameterizations of the quark Sivers function and the Burkardt sum rule (BSR) for the Sivers distributions are also discussed.