We consider the phenomenological description of the two pion invariant mass spectrum in the $V^{\prime }\to V\pi \pi$ decays. We study the parametrization of the amplitude involving both S and D wave contributions. From a fit to the two pion decays of the ${\rm Y}\mathrm{}\left(\mathrm{nS}\right)\mathrm{}$ and $\Psi \mathrm{}\left(\mathrm{nS}\right)\mathrm{}$ we determine the $f_0\mathrm{}\left(600\right)\mathrm{}$ mass and width to be $m_{f_0}=528\mathrm{}\pm 32\mathrm{MeV}$ and ${\Gamma }_{f_0}=413\mathrm{}\pm 45\mathrm{MeV}.$ The mass and width values we report correspond, respectively, to the real and imaginary part of the S matrix pole.

We present a detailed examination of the heavy flavor properties of jets produced at the Fermilab Tevatron collider. The data set, collected with the Collider Detector at Fermilab, consists of events with two or more jets with transverse energy $E_T>~15\mathrm{GeV}$ and pseudorapidity $|\eta |<~\mathrm{1.5.}$ The heavy flavor content of the data set is enriched by requiring that at least one of the jets (lepton-jet) contains a lepton with a transverse momentum larger than $8\mathrm{GeV}/c.\mathrm{}$ Jets containing hadrons with heavy flavor are selected via the identification of secondary vertices. The parton-level cross sections predicted by the HERWIG Monte Carlo generator program are tuned within theoretical and experimental uncertainties to reproduce the secondary-vertex rates in the data. The tuned simulation provides new information on the origin of the discrepancy between the $b\overline{b}$ cross section measurements at the Tevatron and the next-to-leading order QCD prediction. We also compare the rate of away-jets (jets recoiling against the lepton-jet) containing a soft lepton ${(p}_T>~2\mathrm{GeV}/c)$ in the data to that in the tuned simulation. We find that this rate is larger than what is expected for the conventional production and semileptonic decay of pairs of hadrons with heavy flavor.

The problem of the stabilization of moduli is discussed within the context of compactified strongly coupled heterotic string theory. It is shown that all geometric, vector bundle, and five-brane moduli are completely fixed, within a phenomenologically acceptable range, by nonperturbative physics. This result requires, in addition to the full space of moduli, nonvanishing Neveu-Schwarz flux, gaugino condensation with threshold corrections, and the explicit form of the Pfaffians in string instanton superpotentials. The stable vacuum presented here has a negative cosmological constant. The possibility of “lifting” this to a metastable vacuum with positive cosmological constant is briefly discussed.

A general class of rotating closed string solutions in ${\mathrm{AdS}}_5\times {\mathrm{S}}^5$ is shown to be described by a Neumann-Rosochatius one-dimensional integrable system. The latter represents an oscillator on a sphere or a hyperboloid with an additional “centrifugal” potential. We expect that the reduction of the ${\mathrm{AdS}}_5\times {\mathrm{S}}^5$ sigma model to the Neumann-Rosochatius system should have further generalizations and should be useful for uncovering new relations between integrable structures on two sides of the AdS/conformal field theory (CFT) duality. We find, in particular, new circular rotating string solutions with two ${\mathrm{AdS}}_5$ and three ${\mathrm{S}}^5$ spins. As in other recently discussed examples, the leading large-spin correction to the classical energy turns out to be proportional to the square of the string tension or the ’t Hooft coupling $\lambda ,$ suggesting that it can be matched onto the one-loop anomalous dimensions of the corresponding “long” operators on the super-Yang-Mills side of the AdS/CFT duality.

We show that fractional flux from Wilson lines can stabilize the moduli of heterotic string compactifications on Calabi-Yau threefolds. We observe that the Wilson lines used in GUT symmetry breaking naturally induce a fractional flux. When combined with a hidden-sector gaugino condensate, this generates a potential for the complex structure moduli, Kähler moduli, and dilaton. This potential has a supersymmetric AdS minimum at moderately weak coupling and large volume. Notably, the necessary ingredients for this construction are often present in realistic models. We explore the type IIA dual phenomenon, which involves Wilson lines in D6-branes wrapping a three-cycle in a Calabi-Yau threefold, and comment on the nature of the fractional instantons that change the Chern-Simons invariant.

The full set of equations governing the evolution of self-gravitating spherically symmetric dissipative fluids with anisotropic stresses is deployed and used to carry out a general study on the behavior of such systems, in the context of general relativity. Emphasis is given to the link between the Weyl tensor, the shear tensor, the anisotropy of the pressure, and the density inhomogeneity. In particular we provide the general, necessary, and sufficient condition for the vanishing of the spatial gradients of energy density, which in turn suggests a possible definition of a gravitational arrow of time. Some solutions are also exhibited to illustrate the discussion.

The holographic principle relates (classical) gravitational waves in the bulk to quantum fluctuations and the Weyl anomaly of a conformal field theory on the boundary (the brane). One can thus argue that linear perturbations in the bulk of static black holes located on the brane be related to the Hawking flux and that (brane-world) black holes are therefore unstable. We try to gain some information on such instability from established knowledge of the Hawking radiation on the brane. In this context, the well-known trace anomaly is used as a measure of both the validity of the holographic picture and of the instability for several proposed static brane metrics. In light of the above analysis, we finally consider a time-dependent metric as the (approximate) representation of the late stage of evaporating black holes which is characterized by decreasing Hawking temperature, in qualitative agreement with what is required by energy conservation.

We study the evolution of perturbations during the domination and decay of a massive particle species whose mass and decay rate are allowed to depend on the expectation value of a light scalar field. We specialize in the case where the light field is slow rolling, showing that during a phase of inhomogeneous mass domination and decay the isocurvature perturbation of the light field is converted into a curvature perturbation with an efficiency which is nine times larger than when the mass is fixed. We derive a condition on the annihilation cross section and on the decay rate for the domination of the massive particles and we show that standard model particles cannot dominate the universe before nucleosynthesis. We also compare this mechanism with the curvaton model. Finally, observational signatures are discussed. A cold dark matter isocurvature mode can be generated if the dark matter is produced out of equilibrium by both the inflaton and the massive particle species decay. Non-Gaussianities are present: they are chi-square deviations. However, they might be too small to be observable.

We present a numerical integration of the cosmological scalar perturbation equations in warm inflation. The initial conditions are provided by a discussion of the thermal fluctuations of an inflaton field and thermal radiation using a combination of thermal field theory and thermodynamics. The perturbation equations include the effects of a damping coefficient $\Gamma$ and a thermodynamic potential V. We give an analytic expression for the spectral index of scalar fluctuations in terms of a new slow-roll parameter constructed from $\Gamma .$ A series of toy models, inspired by spontaneous symmetry breaking and a known form of the damping coefficient, lead to a spectrum with $n_s>1\mathrm{}$ on large scales and $n_s<1\mathrm{}$ on small scales.

We present a detailed analytical study of ultrarelativistic neutrinos in cosmological perturbation theory and of the observable signatures of inhomogeneities in the cosmic neutrino background. We note that modification of perturbation variables that removes all the time derivatives of scalar gravitational potentials from the dynamical equations simplifies their solution notably. The used perturbations of particle number per coordinate, not proper, volume are generally constant on superhorizon scales. In real space the analytical approach can be extended beyond fluid models to neutrinos. The faster cosmological expansion due to the neutrino background affects the acoustic and damping angular scales of the cosmic microwave background (CMB). But we find that equivalent changes can be produced by varying other standard parameters, including the primordial helium abundance. The low-l integrated Sachs-Wolfe effect is also not sensitive to neutrinos. However, the gravity of neutrino perturbations suppresses the CMB acoustic peaks for the multipoles with $l\gtrsim 200$ while it enhances the amplitude of matter fluctuations on these scales. In addition, the perturbations of relativistic neutrinos generate a unique phase shift of the CMB acoustic oscillations that, for adiabatic modes, cannot be caused by any other standard physics. The origin of the shift is traced to neutrino free-streaming velocity exceeding the sound speed of the photon-baryon plasma. We find that from a high-resolution, low-noise instrument such as CMBPOL the effective number of light neutrino species can be determined with an accuracy of $\sigma {(N}_{\nu })\simeq 0.05–0.09,$ depending on the constraints on the helium abundance.

We apply the probability distribution function method to the study of chiral properties of QCD with quarks in the exact massless limit. A relation among the chiral condensate, the zeros of the Bessel function, and the eigenvalue of the Dirac operator is also given. The chiral condensate in this limit can be measured with a small number of eigenvalues of the massless Dirac operator and without any ambiguous mass extrapolation. The results for SU(3) gauge theory with quenched Kogut-Susskind quarks on the ${10}^4$ lattice are shown.

We present results of numerical simulations of the (3+1)-dimensional Nambu–Jona-Lasinio model with a nonzero baryon density enforced via the introduction of a chemical potential $\mu \ne 0.$ The triviality of the model with a number of dimensions $d>~4$ is dealt with by fitting low energy constants, calculated analytically in the large number of colors (Hartree) limit, to phenomenological values. Nonperturbative measurements of local order parameters for superfluidity and their related susceptibilities show that, in contrast with the (2+1)-dimensional model, the ground state at high chemical potential and low temperature is that of a traditional BCS superfluid. This conclusion is supported by the direct observation of a gap in the dispersion relation for $0.5<~\mu a<~0.85,$ which at $\mu a=0.8\mathrm{}$ is found to be roughly 15% the size of the vacuum fermion mass. We also present results of an initial investigation of the stability of the BCS phase against thermal fluctuations. Finally, we discuss the effect of splitting the Fermi surfaces of the pairing partners by the introduction of a nonzero isospin chemical potential.

We present a scenario of nonthermal leptogenesis following supersymmetric hybrid inflation, in the case where inflaton decay to both heavy right-handed neutrino and $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_L$ triplet superfields is kinematically disallowed. Lepton asymmetry is generated through the decay of the inflaton into light particles by the interference of one-loop diagrams with right-handed neutrino and $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_L$ triplet exchange, respectively. We require superpotential couplings explicitly violating a U(1) R symmetry and R parity. However, the broken R parity need not have currently observable low-energy signatures. Also, the lightest sparticle can be stable. Some R-parity-violating slepton decays may, though, be detectable in future colliders. We take into account the constraints from neutrino masses and mixing and the preservation of the primordial lepton asymmetry.

New couplings of the chemical potential, closer to the continuum, are derived from the transfer matrix formulation of the partition function of QCD on a lattice. In particular the time splitting of the quark fields (and therefore the presence of the temporal gauge fields) can be avoided in some of these couplings.

In $\mathrm{SU}\left(2\right)\mathrm{}$ lattice pure gauge theory we study numerically the dependence of the ghost propagator $G\left(p\right)\mathrm{}$ on the choice of Gribov copies in the Lorentz (or Landau) gauge. We find that the effect of Gribov copies is essential in the scaling window region; however, it tends to decrease with increasing β. On the other hand, we find that at larger β values very strong fluctuations appear which can make problematic the calculation of the ghost propagator.

We show that the confining property of the one-gluon propagator, in the Coulomb gauge, is linked to the unbroken realization of a remnant gauge symmetry which exists in this gauge. An order parameter for the remnant gauge symmetry is introduced, and its behavior is investigated in a variety of models via numerical simulations. We find that the color-Coulomb potential, associated with the gluon propagator, grows linearly with distance both in the confined and—surprisingly—in the high-temperature deconfined phase of pure Yang-Mills theory. We also find a remnant symmetry-breaking transition in SU(2) gauge-Higgs theory which completely isolates the Higgs region from the (pseudo)confinement region of the phase diagram. This transition exists despite the absence, pointed out long ago by Fradkin and Shenker, of a genuine thermodynamic phase transition separating the two regions.

Recently, it has been pointed out that there exists a connection between the generalized parton distribution $E(x,0,t)\mathrm{}$ and the Sivers effect for single-spin asymmetries. For transversely polarized nucleon targets, generalized parton distributions are asymmetric in impact parameter space. This impact parameter space asymmetry, together with the final state interaction of the active quark, gives rise to the Sivers effect in momentum space. We demonstrate this phenomenon explicitly in the scalar diquark model. This result also illustrates the physics that underlies the correlation between the anomalous magnetic moment and the Sivers effect for a given quark flavor.

We consider the role of the Faddeev-Popov determinant in the Coulomb gauge on the confinement properties of the QCD vacuum. We show that the determinant is needed to regularize the otherwise divergent functional integrals near the Gribov horizon but still enables large field configurations to generate IR enhanced running coupling. The physical gluon propagator is found to be strongly suppressed in the IR consistent with expectations from lattice gauge calculations.

It is shown that the type III seesaw mechanism proposed recently can have certain advantages over the conventional (or type I) seesaw mechanism for leptogenesis. In particular a resonant enhancement of leptogenesis via heavy quasi-Dirac right-handed neutrino pairs can occur without a special flavor form or “texture” of the mass matrices being assumed. Some of the requirements for neutrino mixing and leptogenesis are effectively decoupled.

We study the radiation of energy and linear momentum emitted to infinity by the head-on collision of binary black holes, starting from rest at a finite initial separation, in the extreme mass ratio (particle) limit. For these configurations we identify the radiation that may be attributed to a choice of the initial three geometry. This identification suggests that for evolution of holes from initial proper separations $L_0>~7M,$ the radiated energy and momentum from head-on collisions will not be dominated by that choice. For non-head-on orbits, where the amount of radiation is orders of magnitude larger, computations may be even less sensitive to the choice of initial three geometry.