We reconsider a universal mass matrix model which has a seesaw-invariant structure with four-zero texture common to all quarks and leptons. The Cabibbo-Kobayashi-Maskawa (CKM) quark and Maki-Nakagawa-Sakata (MNS) lepton mixing matrices of the model are analyzed analytically. We show that the model can be consistent with all the experimental data of neutrino oscillation and quark mixings by tuning free parameters of the model. It is also shown that the model predicts a relatively large value for the (1, 3) element of the MNS lepton mixing matrix, $|(U_{\mathrm{MNS}}{)}_{13}{|}^2\simeq (0.041–9.6)\times {10}^{-2}$. Using the seesaw mechanism, we also discuss the conditions for the components of the Dirac and the right-handed Majorana neutrino mass matrices which lead to the neutrino mass matrix consistent with the experimental data.

It is shown that one can in principle constrain the $CP$-violating parameter $\delta$ from measurements of four independent $|V_{ij}{|}^2$’s, or three $|V_{ij}{|}^2$’s and a ratio of two of them, in the leptonic sector. To quantify our approach, using unitarity, we derive simple expressions in terms of four independent $|V_{ij}{|}^2$’s for $\cos \delta$, and an expression for ${sin}^2\delta$ from $J^2$. Thus, depending on the values for $|V_{ij}|$ and their accuracy, we can set meaningful limits on $|\delta |$. To illustrate numerically, if $|V_{\mu 1}{|}^2$ is close to 0.1 with a 10% precision, and if $|V_{e3}{|}^2$ is larger than 0.005 and for values of $|V_{e2}{|}^2$ and $|V_{\mu 3}{|}^2$ that stay within $\pm 0.1$ of the current experimental data leads to a bound: $\pi /2\le |\delta |\le \pi$. Alternatively, a certain combination of parameters with values of $|V_{e3}{|}^2$ larger than 0.01 leads to a closed bound of $73\le |\delta |\le 103$. In general, we find that it is better to use $|V_{\mu 1}{|}^2$ or $|V_{\tau 1}{|}^2$ as the fourth independent $|V_{ij}{|}^2$ and that, over most of the parameter space, $\delta$ is least sensitive to $|V_{e3}{|}^2$. With just three independent measurements (solar, atmospheric, and reactor), it is impossible to set limits on the $CP$ phase. In this respect, we study the use of ultrahigh energy cosmic ray neutrino fluxes as the additional fourth information. We find that within the SM, neutrino fluxes of all three flavors will be very similar but that pushing current neutrino data to their extreme values still allowed, ratios of cosmic neutrino fluxes can differ by up to 20%; such large discrepancies could imply negligibly small $CP$ violation. We also study a nonradiative neutrino decay model and find that the neutrino fluxes can differ by a factor of up to 3 within this model and that an accuracy of 10% on the neutrino fluxes is sufficient to set interesting limits on $\delta$.

We describe a measurement of the top quark mass using events with two charged leptons collected by the CDF II detector from $p\overline{p}$ collisions with $\sqrt{s}=1.96\mathrm{TeV}$ at the Fermilab Tevatron. The likelihood in top quark mass is calculated for each event by convoluting the leading order matrix element describing $q\overline{q}\to t\overline{t}\to b\ell {\nu }_{\ell }\overline{b}{\ell }^{\prime }{\nu }_{{\ell }^{\prime }}$ with detector resolution functions. The presence of background events in the data sample is modeled using similar calculations involving the matrix elements for major background processes. In a data sample with integrated luminosity of $340{\mathrm{pb}}^{-1}$, we observe 33 candidate events and measure $M_{\mathrm{top}}=165.2\pm 6.1(\mathrm{stat}.)\pm 3.4(\mathrm{syst}.)\mathrm{GeV}/c^2.$ This measurement represents the first application of this method to events with two charged leptons and is the most precise single measurement of the top quark mass in this channel.

We present a measurement of $R_{\mathcal{B}}$, the ratio of the branching fraction for the rare decay $D^0\to K^{+}{\pi }^{-}$ to that for the Cabibbo-favored decay $D^0\to K^{-}{\pi }^{+}$. Charge-conjugate decays are implicitly included. A signal of $2005\pm 104$ events for the decay $D^0\to K^{+}{\pi }^{-}$ is obtained using the CDF II detector at the Fermilab Tevatron collider. The data set corresponds to an integrated luminosity of $0.35{\mathrm{fb}}^{-1}$ produced in $\overline{p}p$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$. Assuming no mixing, we find $R_{\mathcal{B}}=[4.05\pm 0.21(\mathrm{stat})\pm 0.11(\mathrm{syst})]\times {10}^{-3}$. This measurement is consistent with the world average, and comparable in accuracy with the best measurements from other experiments.

Charged vortex solutions for the noncommutative Maxwell-Higgs model in $3+1$ dimensions are found. We show that the stability of these vortex solutions is lost for some, large enough, noncommutativity parameters. A nontopological charge, however, is induced by noncommutative effects.

The large $N$ reductions in gauge theories are identified with dimensional reductions with homogeneous distribution of the eigenvalues of the gauge fields, and it is used to identify the corresponding closed string descriptions in the Maldacena duality. When one does not take the zero-radii limit, the large $N$ reductions are naturally extended to the equivalences between the gauge theories and the “generalized” reduced models, which naturally contain the notion of $T$-dual equivalence. In the dual gravitational description, $T$-duality relates two type IIB supergravity solutions, the near horizon geometry of $D3$-branes, and the near horizon geometry of $D$-instantons distributed densely and homogeneously on the dual torus. This is the holographic description of the generalized large $N$ reductions.

We develop a supersymmetric extension of Chern-Simons theory and Chern-Simons-Landau-Ginzburg theory for the supersymmetric quantum Hall liquid. Supersymmetric counterparts of topological and gauge structures peculiar to the Chern-Simons theory are inspected in the supersymmetric Chern-Simons theory. We also explore an effective field theoretical description for the supersymmetric quantum Hall liquid. The key observation is the charge-flux duality. Based on the duality, we derive a dual supersymmetric Chern-Simons-Landau-Ginzburg theory, and discuss physical properties of the topological excitations in the supersymmetric quantum Hall liquid.

We analyze the large-order behavior of the perturbative weak-field expansion of the effective Lagrangian density of a massive scalar in de Sitter and anti–de Sitter space, and show that this perturbative information is not sufficient to describe the nonperturbative behavior of these theories, in contrast to the analogous situation for the Euler-Heisenberg effective Lagrangian density for charged scalars in constant electric and magnetic background fields. For example, in even-dimensional de Sitter space there is particle production, but the effective Lagrangian density is nevertheless real, even though its weak-field expansion is a divergent nonalternating series whose formal imaginary part corresponds to the correct particle production rate. This apparent puzzle is resolved by considering the full nonperturbative structure of the relevant Feynman propagators, and cannot be resolved solely from the perturbative expansion.

Future generation gravitational wave interferometric detectors will require a strong reduction of thermal noise, and will be limited by quantum fluctuations of laser light, namely, shot noise and radiation pressure noise. One of the factors which currently constrain the thermal noise performances of this kind of instruments is the dissipation introduced by the optical coating of the mirrors. In a recent article Braginsky and Vyatchanin proposed to reduce the contribution of thermoelastic noise in the coating building an optical cavity with corner reflectors instead of spherical mirrors. In this work we study a solution which, avoiding completely any kind of coating, allows for injection and extraction of light. We discuss the proposed optical scheme, evaluating the expected thermal noise performances.

The Super-Kamiokande atmospheric neutrino measurements leave substantial room for nonstandard interactions (NSI) of neutrinos with matter in the ${\nu }_e\mathrm{\text{−}}{\nu }_{\tau }$ sector. Large values of the NSI couplings are accommodated if the vacuum oscillation parameters are changed from their standard values. Short and medium baseline neutrino beams can break this degeneracy by measuring the true vacuum oscillation parameters with the ${\nu }_{\mu }$ disappearance mode, for which the matter effects are negligible or subdominant. These experiments can also search for the ${\nu }_e\mathrm{\text{−}}{\nu }_{\tau }$ flavor-changing effects directly, by looking for ${\nu }_{\mu }\mathrm{\text{−}}{\nu }_e$ conversion caused by the intervening matter. We discuss both of these methods for the case of MINOS. We find that, while the present MINOS data on ${\nu }_{\mu }$ disappearance induce only minor changes on the constraints on the NSI parameters, the situation will improve markedly with the planned increase of the statistics by an order of magnitude. In that case, the precision will be enough to distinguish certain presently allowed NSI scenarios from the no-NSI case. NSI per quark of about 10% the size of the standard weak interaction could give a ${\nu }_{\mu }\mathrm{\text{−}}{\nu }_e$ conversion probability of the order $\sim {10}^{-2}$, measurable by MINOS in the same high statistics scenario. In this ${\nu }_{\mu }\mathrm{\text{−}}{\nu }_e$ channel, the small effects of NSI could be comparable or larger than the vacuum contribution of the small angle ${\theta }_{13}$. The expected ${\theta }_{13}$ bound at MINOS should be more properly interpreted as a bound in the ${\theta }_{13}$-NSI parameter space.

We derive the equation for the quasinormal modes corresponding to the scalar excitation of a black hole moving away in the fifth dimension. This geometry is the AdS/CFT dual of a boost-invariant expanding perfect fluid in $\mathcal{N}=4$ SUSY Yang-Mills theory at large proper-time. On the gauge-theory side, the dominant solution of the equation describes the decay back to equilibrium of a scalar excitation of the perfect fluid. Its characteristic proper-time can be interpreted as a thermalization time of the perfect fluid, which is a universal (and numerically small) constant in units of the unique scale of the problem. This may provide a new insight on the short thermalization-time puzzle encountered in heavy-ion collision phenomenology. A nontrivial scaling behavior in proper-time is obtained which can be interpreted in terms of a slowly varying adiabatic approximation.

Recently Liu, Rajagopal, and Wiedemann (LRW) [H. Liu, K. Rajagopal, and U. A. Wiedemann, hep-ph/0605178.] proposed a first principle, nonperturbative quantum field theoretic definition of “jet quenching parameter” $\widehat{q}$ used in models of medium-induced radiative parton energy loss in nucleus-nucleus collisions at RHIC. Relating $\widehat{q}$ to a short-distance behavior of a certain lightlike Wilson loop, they used gauge theory-string theory correspondence to evaluate $\widehat{q}$ for the strongly coupled $\mathcal{N}=4$ $SU(N_c)$ gauge theory plasma. We generalize analysis of LRW to strongly coupled nonconformal gauge theory plasma. We find that a jet quenching parameter is gauge theory specific (not universal). Furthermore, it appears its value increases as the number of effective adjoint degrees of freedom of a gauge theory plasma increases.

We compute spectral densities of momentum and $R$-charge correlators in thermal $\mathcal{N}=4$ Yang-Mills theory at strong coupling. For $\omega \sim T$ and smaller, the spectral density differs markedly from perturbation theory; there is no kinetic theory peak. For large $\omega$, the spectral density oscillates around the zero temperature result with an exponentially decreasing amplitude. Contrast this with QCD where the spectral density of the current-current correlator approaches the zero temperature result like $(T/\omega {)}^4$. This difference is related to the absence of cuts in the retarded Green function in $\mathcal{N}=4$ Yang-Mills theory at strong coupling. Despite these marked differences with perturbation theory, in Euclidean space-time the correlators differ by only $\sim 10\%$ from the free result. The implications for lattice QCD measurements of transport are discussed.

It is known that the presence of the antisymmetric background field $B_{\mu \nu }$ leads to the noncommutativity of the Dp-brane manifold. The addition of the linear dilaton field in the form $\Phi (x)={\Phi }_0+a_{\mu }{x}^{\mu }$ causes the appearance of the commutative Dp-brane coordinate $x=a_{\mu }{x}^{\mu }$. In the present article we show that for some particular choices of the background fields, $a^2\equiv G^{\mu \nu }{a}_{\mu }{a}_{\nu }=0$ and ${\tilde{a}}^2\equiv [(G-4B{G}^{-1}B{)}^{-1}{]}^{\mu \nu }{a}_{\mu }{a}_{\nu }=0$, the local gauge symmetries appear in the theory. They turn some Neuman boundary conditions into the Dirichlet ones, and consequently decrease the number of the Dp-brane dimensions.

Electrically charged solutions for gravity with a conformally coupled scalar field are found in four dimensions in the presence of a cosmological constant. If a quartic self-interaction term for the scalar field is considered, there is a solution describing an asymptotically locally AdS charged black hole dressed with a scalar field that is regular on and outside the event horizon, which is a surface of negative constant curvature. This black hole can have negative mass, which is bounded from below for the extremal case, and its causal structure shows that the solution describes a “black hole inside a black hole”. The thermodynamics of the nonextremal black hole is analyzed in the grand canonical ensemble. The entropy does not follow the area law, and there is an effective Newton constant which depends on the value of the scalar field at the horizon. If the base manifold is locally flat, the solution has no electric charge, and the scalar field has a vanishing stress-energy tensor so that it dresses a locally AdS spacetime with a nut at the origin. In the case of vanishing self interaction, the solutions also dress locally AdS spacetimes, and if the base manifold is of negative constant curvature a massless electrically charged hairy black hole is obtained. The thermodynamics of this black hole is also analyzed. It is found that the bounds for the black holes parameters in the conformal frame obtained from requiring the entropy to be positive are mapped into the ones that guarantee cosmic censorship in the Einstein frame.

We explore the dynamics of dark energy models based on a Dirac-Born-Infeld (DBI) tachyonic action, studying a range of potentials. We numerically investigate the existence of tracking behavior and determine the present-day value of the equation of state parameter and its running, which are compared with observational bounds. We find that tachyon models have quite similar phenomenology to canonical quintessence models. While some potentials can be selected amongst many possibilities and fine-tuned to give viable scenarios, there is no apparent advantage in choosing a DBI scalar field instead of a Klein-Gordon one.

Bulk viscosity may serve to damp sound waves in a system of neutrinos coupled to very light scalar particles, in the era after normal neutrino decoupling but before recombination. We calculate the bulk viscosity parameter in a minimal scheme involving the coupling of the two systems. We add some remarks on the bulk viscosity of a system of fully ionized hydrogen plus photons.

The sources of the observed ultrahigh energy cosmic rays must also generate ultrahigh energy neutrinos. Deep inelastic scattering of these neutrinos with nucleons on Earth probe center-of-mass energies $\sqrt{s}\sim 100\mathrm{TeV}$, well beyond those attainable at terrestrial colliders. By comparing the rates for two classes of observable events, any departure from the benchmark (unscreened perturbative QCD) neutrino-nucleon cross section can be constrained. Using the projected sensitivity of the Pierre Auger Observatory to quasihorizontal showers and Earth-skimming tau neutrinos, we show that a “super-Auger” detector can thus provide an unique probe of strong interaction dynamics.

We, first, attempt to single out the measures of cosmological perturbations that are least afflicted by gauge artifacts and directly connect inhomogeneous large-scale evolution with microscopic kinetics and interactions. We seek perturbation measures (i) whose dynamics is completely specified by the physics within the local Hubble volume and (ii) which are practically applicable on microscopic scales and retain their microscopic physical meaning on all scales in any homogeneous and isotropic geometry. We identify such natural measures for linear perturbations of species’ density, and for nonlinear perturbations of phase-space distribution and radiation intensity. When these measures are applied to linear evolution in the Newtonian gauge, the equations acquire an explicit Cauchy structure and nonsingular superhorizon limit, while their solutions simplify. We prove that all measures of linear overdensity that satisfy (i) and (ii) coincide in the superhorizon limit. We then show that, contrary to the prevailing view, the perturbations of the cosmic microwave background (CMB) are not resonantly boosted by their self-gravity at horizon entry in the radiation era. This explains the mildness of the CMB signatures caused by the dark species which may be abundant in the radiation era, e.g. neutrinos or early quintessence. Such species can still be well constrained due to their characteristic nondegenerate signatures on scales $\ell \gtrsim 200$, where the cosmic variance is low. We find, on the other hand, that the dark matter inhomogeneities in the matter era gravitationally suppress large-angle CMB anisotropy by an order of magnitude stronger than previously stated. (In a cosmology dominated by pressureless matter, the suppression of CMB temperature autocorrelation $C_{\ell }$ is 25-fold.) Hence, despite the larger cosmic variance at the affected $\ell \lesssim 200$, the CMB anisotropy on these scales is a useful probe of the dark sectors in the matter era.

Production of even-parity charmed mesons in hadronic $B$ decays is studied. Specifically, we focus on the Cabibbo-allowed decays $\overline{B}\to D^{**}\pi$ and ${\overline{D}}_s^{**}{D}^{(*)}$, where $D^{**}$ denotes generically a $P$-wave charmed meson. While the measured color-allowed decays ${\overline{B}}^0\to D^{**+}{\pi }^{-}$ are consistent with the theoretical expectation, the experimental observation of $B^{-}\to D^{**0}{\pi }^{-}$ for the broad $D^{**}$ states is astonishing as it requires that the color-suppressed contribution dominates over the color-allowed one, even though the former is $1/m_b$ suppressed in the heavy quark limit. In order to accommodate the data of $\overline{B}\to D^{**}{\pi }^{-}$, it is found that the real part of $a_2/a_1$ has a sign opposite to that in $\overline{B}\to D\pi$ decays, where $a_1$ and $a_2$ are the effective parameters for color-allowed and color-suppressed decay amplitudes, respectively. The decay constants and form factors for $D^{**}$ and the Isgur-Wise functions ${\tau }_{1/2}(\omega )$ and ${\tau }_{3/2}(\omega )$ are extracted from the data of $B\to D^{**}\pi$ decays. The Isgur-Wise functions calculated in the covariant light-front quark model are in good agreement with experiment. The neutral modes ${\overline{B}}^0\to D^{**0}{\pi }^0$ for $D^{**}=D_0^{*}(2400)$, $D_1^{\prime }(2430)$, and ${\overline{B}}^0\to D_1^{\prime 0}(2430)\omega$ are predicted to have branching ratios of order ${10}^{-4}$ which are also supported by the isospin argument. The decay constants of $D_{s0}^{*}(2317)$ and $D_{s1}^{\prime }(2460)$ are inferred from the measurements of $\overline{B}\to D_s^{**-}D$ to be 58–86 MeV and 130–200 MeV, respectively. Contrary to the decay constants $f_{D_0^{*}}$ and $f_{D_1^{\prime }}$ which are similar in size, the large disparity between $f_{D_{s0}^{*}}$ and $f_{D_{s1}^{\prime }}$ is surprising and unexpected.