The processes ${\psi }^{\prime }\to p\overline{p}{\pi }^0$ and ${\psi }^{\prime }\to p\overline{p}\eta$ are studied using a sample of $14\times {10}^6$ ${\psi }^{\prime }$ decays collected with the Beijing Spectrometer at the Beijing Electron-Positron Collider. The branching fraction of ${\psi }^{\prime }\to p\overline{p}{\pi }^0$ is measured with improved precision as $(13.2\pm 1.0\pm 1.5)\times {10}^{-5}$, and ${\psi }^{\prime }\to p\overline{p}\eta$ is observed for the first time with a branching fraction of $(5.8\pm 1.1\pm 0.7)\times {10}^{-5}$, where the first errors are statistical and the second ones are systematic.

We calculate and identify the counterparts of zero-norm states in the old covariant first quantized (OCFQ) spectrum of open bosonic string in two other quantization schemes of string theory, namely, the light-cone Del Giudice–Di Vecchia–Fubine zero-norm states and the off-shell Becchi-Rouet-Stora-Tyutin (BRST) zero-norm states (with ghost) in the Witten string field theory (WSFT). In particular, special attention is paid to the interparticle zero-norm states in all quantization schemes. For the case of the off-shell BRST zero-norm states, we impose the no-ghost conditions and recover exactly two types of on-shell zero-norm states in the OCFQ string spectrum for the first few low-lying mass levels. We then show that off-shell gauge transformations of WSFT are identical to the on-shell stringy gauge symmetries generated by two types of zero-norm states in the generalized massive $\sigma$-model approach of string theory. The high-energy limit of these stringy gauge symmetries was recently used to calculate the proportionality constants, conjectured by Gross, among high-energy scattering amplitudes of different string states. Based on these zero-norm state calculations, we have thus related gauge symmetry of WSFT to the high-energy stringy symmetry of Gross.

We determine the dispersion relations of fermionic quasiparticles in ultradegenerate plasmas by a complete evaluation of the on-shell hard-dense-loop-resummed one-loop fermion self energy for momenta of the order of the Fermi momentum and above. In the case of zero temperature, we calculate the nonanalytic terms in the vicinity of the Fermi surface beyond the known logarithmic approximation, which turn out to involve fractional higher powers in the energy variable. For nonzero temperature (but much smaller than the chemical potential), we obtain the analogous expansion in closed form, which is then analytic but involves polylogarithms. These expansions are compared with a full numerical evaluation of the resulting group velocities and damping coefficients.

We present new cosmological solutions for brane gases with solitonic fluxes that can dynamically explain the existence of three large spatial dimensions. This reasserts the importance of fluxes for understanding the full space of solutions in a potential implementation of the Brandenberger-Vafa mechanism with M2-branes. Additionally, we study a particular example in which the cosmological dynamics supported by a string gas with a Neveu-Schwarz flux in the ten-dimensional dilaton-gravity framework is asymptotically equivalent to that of a M2-brane gas with a certain wrapping configuration in eleven-dimensional supergravity. We speculate that this connection between the ten- and eleven-dimensional implementations of the Brandenberger-Vafa mechanism could be a general feature.

We look at a gas of dust and investigate how its entropy evolves with time under a spherically symmetric gravitational collapse. We treat the problem perturbatively and find that the classical thermodynamic entropy does actually increase to first order when one allows for gravitational potential energy to be transferred to thermal energy during the collapse. Thus, in this situation there is no need to resort to the introduction of an intrinsic gravitational entropy in order to satisfy the second law of thermodynamics.

We have carried out numerical simulations of strongly gravitating systems based on the Einstein equations coupled to the relativistic hydrodynamic equations using adaptive mesh refinement (AMR) techniques. We show AMR simulations of NS binary inspiral and coalescence carried out on a workstation having an accuracy equivalent to that of a ${1025}^3$ regular unigrid simulation, which is, to the best of our knowledge, larger than all previous simulations of similar NS systems on supercomputers. We believe the capability opens new possibilities in general relativistic simulations.

We study vacuum alignment in theories in which the chiral symmetry of a set of massless fermions is both spontaneously and explicitly broken. We find that transitions occur between different phases of the fermions’ $CP$ symmetry as parameters in their symmetry breaking Hamiltonian are varied. We identify a new phase that we call pseudo$CP$-conserving. We observe first and second-order transitions between the various phases. At a second-order (and possibly first-order) transition a pseudo-Goldstone boson becomes massless as a consequence of a spontaneous change in the discrete, but not the continuous, symmetry of the ground state. We relate the masslessness of these “accidental Goldstone bosons” (AGBs) to singularities of the order parameter for the phase transition. The relative frequency of $CP$-phase transitions makes it commonplace for the AGBs to be light, much lighter than their underlying strong interaction scale. We investigate the AGBs’ potential for serving as light composite Higgs bosons by studying their vacuum expectation values, finding encouraging results: AGB vevs are also often much less than their strong scale.

We present arguments regarding the possible role of diquarks in low-energy hadron phenomenology that has so far escaped theorists’ attention. Good diquarks, i.e. the $0^{+}$ states of two quarks, are argued to have a two-component structure with one of the components peaking at distances several times shorter than a typical hadron size (a short-range core). This can play a role in solving two old puzzles of the ’t Hooft $1/N$ expansion: strong quark-mass dependence of vacuum energy density and strong violations of the Okubo-Zweig-Iizuka (OZI) rule in quark-antiquark $0^{\pm }$ channels. In both cases empiric data defy ’t Hooft’s $1/N$ suppression. If good diquarks play a role at an intermediate energy scale they ruin ’t Hooft’s planarity because of their mixed-flavor composition. This new scale associated with good diquarks may be related to a numerically large scale discovered in [V. A. Novikov, M. A. Shifman, A. I. Vainshtein, and V. I. Zakharov, Nucl. Phys. B 191, 301 (1981)] in a number of phenomena mostly related to vacuum quantum numbers and $0^{\pm }$ glueball channels. If $\mathrm{SU}(3{)}_{\mathrm{color}}$ of bona fide QCD is replaced by $\mathrm{SU}(2{)}_{\mathrm{color}}$, diquarks become well-defined gauge-invariant objects. Moreover, there is an exact symmetry relating them to pions. In this limit predictions regarding good diquarks are ironclad. If passage from $\mathrm{SU}(2{)}_{\mathrm{color}}$ to $\mathrm{SU}(3{)}_{\mathrm{color}}$ does not lead to dramatic disturbances, these predictions remain qualitatively valid in bona fide QCD.

We discuss the stability of strangelets by considering dynamical chiral symmetry breaking and confinement. We use a $U(3{)}_L\times U(3{)}_R$ symmetric Nambu-Jona-Lasinio (NJL) model for chiral symmetry breaking supplemented by a boundary condition for confinement. It is shown that strangelets (finite number of strange quarks) with baryon number $A\lesssim {10}^3$ is the lowest quark droplets. For the observables, we obtain the masses and the charge-to-baryon number ratios of the strangelets. These quantities are compared with the observed data of the exotic particles.

We study the two photon decay of neutral scalars below 1.5 GeV in the context of a recently proposed chiral model for $\overline{q}q$ and $\overline{qq}qq$ states. We find good agreement with experimental results for the $a_0(980)\to \gamma \gamma$ decay. Our calculations for $f_0(980)\to \gamma \gamma$ shows that further work is necessary in order to understand the structure of this meson. The model predicts $\Gamma (a_0(1450)\to \gamma \gamma )=0.16\pm 0.10\mathrm{KeV}$, $\Gamma (\sigma \to \gamma \gamma )=(0–1.13)\mathrm{KeV}$, $\Gamma (f_0(1370)\to \gamma \gamma )=(0–0.22)\mathrm{KeV}$, $\Gamma (f_0(1500)\to \gamma \gamma )=(0–1.51)\mathrm{KeV}$.

There is a good deal of current interest in the condensate $⟨A_{\mu }^a{A}_a^{\mu }⟩$ which has been seen to play an important role in calculations which make use of the operator product expansion. That development has led to the publication of a large number of papers which discuss how that condensate could play a role in a gauge-invariant formulation. In the present work we consider gluon propagation in the presence of such a condensate which we assume to be present in the vacuum. We show that the gluon propagator has no on-mass-shell pole and, therefore, a gluon cannot propagate over extended distances. That is, the gluon is a nonpropagating mode in the gluon condensate. In the present work we discuss the properties of both the Euclidean-space and Minkowski-space gluon propagator. In the case of the Euclidean-space propagator we can make contact with the results of QCD lattice calculations of the propagator in the Landau gauge. With an appropriate choice of normalization constants, we present a unified representation of the gluon propagator that describes both the Minkowski-space and Euclidean-space dynamics in which the $⟨A_{\mu }^a{A}_a^{\mu }⟩$ condensate plays an important role.

We report a measurement of the $t\overline{t}$ production cross section using the CDF II detector at the Fermilab Tevatron. The data consist of events with an energetic electron or muon, missing transverse energy, and three or more hadronic jets, at least one of which is identified as a $b$-quark jet by reconstructing a secondary vertex. The background fraction is determined from a fit of the transverse energy of the leading jet. Using $162\pm 10{\mathrm{pb}}^{-1}$ of data, the total cross section is found to be $6.0\pm 1.6(\mathrm{stat}.)\pm 1.2(\mathrm{syst}.)\mathrm{pb}$, which is consistent with the standard model prediction.

A simple model is constructed which allows to compute modified dispersion relations with effects from loop quantum gravity. Different quantization choices can be realized and their effects on the order of corrections studied explicitly. A comparison with more involved semiclassical techniques shows that there is agreement even at a quantitative level. Furthermore, by contrasting Hamiltonian and Lagrangian descriptions we show that possible Lorentz symmetry violations may be blurred as an artifact of the approximation scheme. Whether this is the case in a purely Hamiltonian analysis can be resolved by an improvement in the effective semiclassical analysis.

It has been suggested that a possible candidate for the present accelerated expansion of the Universe is “phantom energy”. The latter possesses an equation of state of the form $\omega \equiv p/\rho <-1$, consequently violating the null energy condition. As this is the fundamental ingredient to sustain traversable wormholes, this cosmic fluid presents us with a natural scenario for the existence of these exotic geometries. ’Note, however, that the notion of phantom energy is that of a homogeneously distributed fluid. Nevertheless, it can be extended to inhomogeneous spherically symmetric spacetimes, and it is shown that traversable wormholes may be supported by phantom energy. Because of the fact of the accelerating Universe, macroscopic wormholes could naturally be grown from the submicroscopic constructions that originally pervaded the quantum foam. One could also imagine an advanced civilization mining the cosmic fluid for phantom energy necessary to construct and sustain a traversable wormhole. In this context, we investigate the physical properties and characteristics of traversable wormholes constructed using the equation of state $p=\omega \rho$, with $\omega <-1$. We analyze specific wormhole geometries, considering asymptotically flat spacetimes and imposing an isotropic pressure. We also construct a thin shell around the interior wormhole solution, by imposing the phantom energy equation of state on the surface stresses. Using the “volume integral quantifier” we verify that it is theoretically possible to construct these geometries with vanishing amounts of averaged null energy condition violating phantom energy. Specific wormhole dimensions and the traversal velocity and time are also deduced from the traversability conditions for a particular wormhole geometry. These phantom energy traversable wormholes have far-reaching physical and cosmological implications. For instance, an advanced civilization may use these geometries to induce closed timelike curves, consequently violating causality.

A set of sufficient conditions for the generalized covariant entropy bound given by Strominger and Thompson is as follows: Suppose that the entropy of matter can be described by an entropy current $s^a$. Let $k^a$ be any null vector along $L$ and $s\equiv -k^a{s}_a$. Then the generalized bound can be derived from the following conditions: (i) $s^{\prime }\le 2\pi T_{ab}{k}^a{k}^b$, where $s^{\prime }=k^a{\nabla }_{a}s$ and $T_{ab}$ is the stress-energy tensor; (ii) on the initial 2-surface $B$, $s(0)\le -\frac{1}{4}\theta (0)$, where $\theta$ is the expansion of $k^a$. We prove that condition (ii) alone can be used to divide a spacetime into two regions: The generalized entropy bound holds for all light sheets residing in the region where $s<-\frac{1}{4}\theta$ and fails for those in the region where $s>-\frac{1}{4}\theta$. We check the validity of these conditions in FRW flat universe and a scalar field spacetime. Some apparent violations of the entropy bounds in the two spacetimes are discussed. These holographic bounds are important in the formulation of the holographic principle.

We study an important contribution to the electric dipole moment (EDM) of the electron (or quarks) at the two-loop level due to the $W$-EDM in the recently proposed scenario of split supersymmetry. This contribution is independent of the Higgs mass, and it can enhance the previous estimation of the electron (neutron) EDM by 20–$50\%$ (40–$90\%$). Our formula is new in its analytical form.

We show that the Feynman propagator in the light-cone gauge with the Mandelstam-Leibbrandt prescription has a logarithmic growth for large $\tilde{n}·x$ which is related to the presence of a residual gauge invariance. Furthermore, we show that the retarded propagator for the $\tilde{n}·A$ component of the gauge field develops a coordinate dependent mass. We argue that this feature is unphysical and may be eliminated by fixing the residual gauge degrees of freedom.

We derive static spherically symmetric vacuum solutions of the low-energy effective action for the two brane Randall-Sundrum model. The solutions with nontrivial radion belong to a one-parameter family describing traversable wormholes between the branes and a black hole, and were first discovered in the context of Einstein gravity with a conformally coupled scalar field. From a brane world perspective, a distinctive feature of all the solutions with nontrivial radion is a brane intersection about which the bulk geometry is conical but the induced metrics on the branes are regular. Contrary to earlier claims in the literature, we show these solutions are stable under monopole perturbations.

In this paper, following hep-th/0501028, we present a detailed derivation and discussion of the exact gravitational field solutions for a relativistic particle localized on a tensional brane in brane-induced gravity. Our derivation yields the metrics for both the normal branch and the self-inflating branch Dvali, Gabadadze, and Porrati (DGP) braneworlds. They generalize the 4D gravitational shock waves in de Sitter space, and so we compare them to the corresponding 4D general relativity solution and to the case when gravity resides only in the 5D bulk, and there are no brane-localized graviton kinetic terms. We write down the solutions in terms of two-variable hypergeometric functions and find that at short distances the shock wave profiles look exactly the same as in 4D Minkowski space, thus recovering the limit one expects if gravity is to be mediated by a metastable, but long-lived, bulk resonance. The corrections far from the source differ from the long distance corrections in 4D de Sitter space, coming in with odd powers of the distance. We discuss in detail the limiting case on the normal branch when gravity is modified exactly at de Sitter radius, and energy can be lost into the bulk by resonancelike processes. Finally, we consider Planckian scattering on the brane, and find that for a sufficiently small impact parameter it is approximated very closely by the usual 4D description.

Understanding how a field theory propagates the information contained in a given initial state is essential for quantifying the sensitivity of the cosmic microwave background to physics above the Hubble scale during inflation. Here we examine the renormalization of a scalar theory with nontrivial initial conditions in the simpler setting of flat space. The renormalization of the bulk theory proceeds exactly as for the standard vacuum state. However, the short distance features of the initial conditions can introduce new divergences which are confined to the surface on which the initial conditions are imposed. We show how the addition of boundary counterterms removes these divergences and induces a renormalization group flow that depends on the initial conditions.