Pair creation of strings in time-dependent backgrounds is studied from an effective field theory viewpoint, and some possible cosmological applications are discussed. Simple estimates suggest that excited strings may have played a significant role in preheating, if the string tension as measured in the four-dimensional Einstein frame falls a couple of orders of magnitude below the four-dimensional Planck scale.

We calculate the primordial abundances of light elements produced during big bang nucleosynthesis when the fine structure constant and/or the cosmic expansion rate take nonstandard values. We compare them with the recent values of observed D, ${}^4\mathrm{He},$ and ${}^7\mathrm{Li}$ abundances, which show a slight inconsistency among themselves in the standard big bang nucleosynthesis scenario. This inconsistency is not solved by considering either a varying fine structure constant or a nonstandard expansion rate separately but solutions are found by their simultaneous existence.

Weakly interacting massive particles (WIMPs) can be captured by the Earth, where they eventually sink to the core, annihilate, and produce, e.g., neutrinos that can be searched for with neutrino telescopes. The Earth is believed to capture WIMPs not dominantly from the Milky Way halo directly, but instead from a distribution of WIMPs that have diffused around in the solar system due to gravitational interactions with the planets in the solar system. Recently, doubts have been raised about the lifetime of these WIMP orbits due to solar capture. We investigate this issue here by detailed numerical simulations. Compared to earlier estimates, we find that the WIMP velocity distribution is significantly suppressed below about 70 km/s, which results in a suppression of the capture rates mainly for heavier WIMPs (above $\sim 100\mathrm{GeV}).\mathrm{}$ At 1 TeV and above the reduction is almost a factor of 10. We apply these results to the case where the WIMP is a supersymmetric neutralino and find that, within the minimal supersymmetric standard model, the annihilation rates and thus the neutrino fluxes are reduced even more than the capture rates. At high masses (above $\sim 1\mathrm{TeV}),$ the suppression is almost two orders of magnitude. This suppression will make the detection of neutrinos from heavy WIMP annihilations in the Earth much harder compared to earlier estimates.

The possibility to avoid the cosmic initial singularity as a consequence of nonlinear effects on the Maxwell eletromagnetic theory is discussed. For a flat Friedmann-Robertson-Walker (FRW) geometry we derive the general nonsingular solution supported by a magnetic field plus a cosmic fluid and a nonvanishing vacuum energy density. The nonsingular behavior of solutions with a time-dependent $\Lambda \mathrm{}\left(t\right)\mathrm{}$ term are also examined. As a general result, it is found that the functional dependence of $\Lambda \mathrm{}\left(t\right)\mathrm{}$ can uniquely be determined only if the magnetic field remains constant. All these models are examples of bouncing universes which may exhibit an inflationary dynamics driven by the nonlinear corrections of the magnetic field.

Recently the study of a braneworld on the self-gravitating D-brane has been initiated and the gravitational equation has been derived on the brane by holographic and geometrical projection methods. Surprisingly, in common with these two methods, the matter on the brane cannot be the source of the gravity on the brane at leading order. In this paper we will propose a low energy effective action on the D-brane coupled with gravity which derives the same results.

We report on a search for gravitational waves from coalescing compact binary systems in the Milky Way and the Magellanic Clouds. The analysis uses data taken by two of the three LIGO interferometers during the first LIGO science run and illustrates a method of setting upper limits on inspiral event rates using interferometer data. The analysis pipeline is described with particular attention to data selection and coincidence between the two interferometers. We establish an observational upper limit of $\mathcal{R}<1.7\mathrm{}\times {10}^2$ per year per Milky Way Equivalent Galaxy (MWEG), with 90% confidence, on the coalescence rate of binary systems in which each component has a mass in the range $1–3M_{\odot }.$

In previous analyses of the Oklo (Gabon) natural reactor to test for a possible time variation of the fine-structure constant $\alpha ,$ a Maxwell-Boltzmann low energy neutron spectrum was assumed. We present here an analysis where a more realistic spectrum is employed and show that the most recent isotopic analysis of samples implies a decrease in $\alpha ,$ over the last $2\times {10}^9$ years since the reactor was operating, of $\left({\alpha }_{\mathrm{past}}-{\alpha }_{\mathrm{now}}\right)/\alpha >~4.5\times {10}^{-8}$ $(6\mathrm{}\sigma$ confidence). Issues regarding the interpretation of the shifts of the low energy neutron absorption resonances are discussed.

The neutrino mixing parameters are presented in a number of different ways by the various experiments, e.g., SuperKamiokande, K2K, SNO, KamLAND, and CHOOZ, and also by the Particle Data Group. In this paper, we argue that presenting the data in terms of ${\sin }^2\theta ,$ where $\theta$ is the mixing angle appropriate for a given experiment, has a direct physical interpretation. For current atmospheric, solar, and reactor neutrino experiments, the ${\sin }^2$θ’s are effectively the probabilities of finding a given flavor in a particular neutrino mass eigenstate. The given flavor and particular mass eigenstate vary from experiment to experiment; however, the use of ${\sin }^2\theta$ provides a unified picture of all the data. Using this unified picture we present a graphical way to represent these neutrino mixing parameters which includes the uncertainties. All of this is performed in the context of the present experimental status of three neutrino oscillations.

We study precision electroweak constraints on the close cousin of the littlest Higgs model, the $\mathrm{SU}\left(6\right)/Sp\left(6\right)\mathrm{}$ model. We identify a near-oblique limit in which the heavy $W^{\prime }$ and $B^{\prime }$ decouple from the light fermions, and then calculate oblique corrections, including one-loop contributions from the extended top sector and the two Higgs doublets. We find regions of parameter space that give acceptably small precision electroweak corrections and only mild fine-tuning in the Higgs potential, and also find that the mass of the lightest Higgs boson is relatively unconstrained by precision electroweak data. The fermions from the extended top sector can be as light as $\simeq 1\mathrm{TeV},$ and the $W^{\prime }$ can be as light as $\simeq 1.8\mathrm{TeV}.$ We include an independent breaking scale for the $B^{\prime },$ which can still have a mass as low as a few hundred GeV.

The anomalous couplings of the top quark and the Higgs boson have been studied in an effective theory deduced from the minimal supersymmetric extension of the standard model as the heavy fields are integrated out. Constraints on the parameters of the model from the experimental data of $R_b=\Gamma \left(\overrightarrow{Z}b\overline{b}\right)/\Gamma \left(\overrightarrow{Z}\mathrm{hadrons}\right)$ are obtained.

We perform calculations of the dependence of nuclear magnetic moments on quark masses and obtain limits on the variation of the fine structure constant $\alpha$ and ${(m}_q/{\Lambda }_{\mathrm{QCD}})$ from recent measurements of hydrogen hyperfine (21 cm) and molecular rotational transitions in quasar absorption systems, atomic clock experiments with hyperfine transitions in H, Rb, Cs, ${\mathrm{Yb}}^{+},$ ${\mathrm{Hg}}^{+},$ and optical transition in ${\mathrm{Hg}}^{+}.$ Experiments with ${\mathrm{Cd}}^{+},$ deuterium/hydrogen, molecular ${\mathrm{SF}}_6,$ and Zeeman transitions in ${}^3\mathrm{H}\mathrm{e}/\mathrm{X}\mathrm{e}$ are also discussed.

We study the associated production of bottomonia and Higgs bosons at hadron colliders within the factorization formalism of nonrelativistic quantum chromodynamics providing all contributing partonic cross sections in analytic form. While such processes tend to be suppressed in the standard model, they may have interesting cross sections in its minimal supersymmetric extension, especially at large values of $\tan \beta ,$ where the bottom Yukawa couplings are enhanced. We present numerical results for the processes involving the lighter CP-even $h^0$ boson and the CP-odd $A^0$ boson appropriate for the Fermilab Tevatron and the CERN LHC.

The two-body decays of the extra neutral boson $Z_2$ predicted by the minimal 3-3-1 model are analyzed. At the tree level, it can decay into standard model particles as well as exotic quarks and the new gauge bosons predicted by the model. The decays into a lepton pair are strongly suppressed, with ${Br(Z}_2\to l^{+}{l}^{-})\approx {10}^{-2}$ and ${Br(Z}_2\to {\overline{\nu }}_l\nu )\approx {10}^{-3}.$ In the bosonic sector, $Z_2$ would decay mainly into a pair of bilepton gauge bosons, with a branching ratio below the 0.1 level. The $Z_2$ boson thus has a leptophobic and bileptophobic nature and it would decay dominantly into quark pairs. The anomaly-induced decays $Z_2\to Z_1\gamma$ and $Z_2\to Z_1{Z}_1,$ which occur at the one-loop level, are studied. It is found that ${Br(Z}_2\to Z_1\gamma )\approx {10}^{-9}$ and ${Br(Z}_2\to Z_1{Z}_1)\approx {10}^{-6}$ at most. As for the $Z_2\to W^{+}{W}^{-}$ and $Z_2\to Z_{1}H$ decays, with H a relatively light Higgs boson, they are induced via $Z^{\prime }-Z$ mixing. It is obtained that ${Br(Z}_2\to W^{+}{W}^{-})\approx {10}^{-2}$ and ${Br(Z}_2\to Z_{1}H)\approx {10}^{-5}.$ We also examine the flavor changing neutral current decays $Z_2\to \mathrm{tc}$ and $Z_2\to tu,$ which may have branching fractions as large as ${10}^{-3}$ and ${10}^{-5},$ respectively, and thus may be of phenomenological interest.

We consider right-handed neutrinos propagating in $\delta$ (large) extra dimensions, whose only coupling to standard model fields is the Yukawa coupling to the left-handed neutrino and the Higgs boson. These theories are attractive as they can explain the smallness of the neutrino mass, as has already been shown. We show that if $\delta$ is bigger than 2, there are strong constraints on the radius of the extra dimensions, resulting from the experimental limit on the probability of an active state to mix into the large number of sterile Kaluza-Klein states of the bulk neutrino. We also calculate the bounds on the radius resulting from requiring that perturbative unitarity be valid in the theory, in an imagined Higgs-Higgs scattering channel.

We present the minimal supersymmetric standard model with general broken R parity, focusing on minimal supergravity (MSUGRA). We discuss the origins of lepton number violation in supersymmetry. We have computed the full set of coupled one-loop renormalization-group equations for the gauge couplings, the superpotential parameters, and for all the soft supersymmetry breaking parameters. We provide analytic formulas for the scalar potential minimization conditions which may be iterated to arbitrary precision. We compute the low-energy spectrum of the superparticles and the neutrinos as a function of the small set of parameters at the unification scale in the general basis. Specializing to MSUGRA, we use the neutrino masses to set new bounds on the R-parity violating couplings. These bounds are up to five orders of magnitude stricter than the previously existing ones. In addition, new bounds on the R-parity violating couplings are also derived demanding a nontachyonic sneutrino spectrum. We investigate the nature of the lightest supersymmetric particle and find extensive regions in parameter space where it is not the neutralino. This leads to a novel set of supersymmetric signatures, which we classify.

Electromagnetic properties of the octet mesons as well as the octet and decuplet baryons are augmented in quenched and partially quenched chiral perturbation theory to include $O\left(a\right)\mathrm{}$ corrections due to lattice discretization. We present the results for the $\mathrm{SU}\left(3\right)\mathrm{}$ flavor group in the isospin limit as well as the results for $\mathrm{SU}\left(2\right)\mathrm{}$ flavor with nondegenerate quarks. These corrections will be useful for extrapolation of lattice calculations using Wilson valence and sea quarks, as well as calculations using Wilson sea quarks and Ginsparg-Wilson valence quarks.

We derive a version of non-Abelian Stokes theorem for SU(2) gauge fields in which neither additional integration nor surface ordering are required. The path ordering is eliminated by introducing the instantaneous color orientation of the flux. We also derive the non-Abelian Stokes theorem on the lattice and discuss various terms contributing to the trace of the Wilson loop.

We consider matching from ${\mathrm{SCET}}_{\mathrm{I}},$ which includes ultrasoft and collinear particles, onto ${\mathrm{SCET}}_{\mathrm{II}}$ with soft and collinear particles at one loop. Keeping the external fermions off their mass shell does not regulate all IR divergences in both theories. We give a new prescription to regulate infrared divergences in SCET. Using this regulator, we show that soft and collinear modes in ${\mathrm{SCET}}_{\mathrm{II}}$ are sufficient to reproduce all the infrared divergences of ${\mathrm{SCET}}_{\mathrm{I}}.$ We explain the relationship between IR regulators and an additional mode proposed for ${\mathrm{SCET}}_{\mathrm{II}}.$

We demonstrate that a trigger on hard dijet production at small rapidities allows us to establish a quantitative distinction between central and peripheral collisions in $\overline{p}p$ and pp collisions at Tevatron and LHC energies. Such a trigger strongly reduces the effective impact parameters as compared to minimum bias events. This happens because the transverse spatial distribution of hard partons $\left(x\gtrsim {10}^{-2}\right)$ in the proton is considerably narrower than that of soft partons, whose collisions dominate the total cross section. In the central collisions selected by the trigger, most of the partons with $x\gtrsim {10}^{-2}$ interact with a gluon field whose strength rapidly increases with energy. At LHC (and to some extent already at Tevatron) energies the strength of this interaction approaches the unitarity (“blackbody”) limit. This leads to specific modifications of the final state, such as a higher probability of multijet events at small rapidities, a strong increase of the transverse momenta and depletion of the longitudinal momenta at large rapidities, and the appearance of long-range correlations in rapidity between the forward or backward fragmentation regions. The same pattern is expected for events with production of new heavy particles (Higgs boson, SUSY). Studies of these phenomena would be feasible with the CMS-TOTEM detector setup, and would have considerable impact on the exploration of the physics of strong gluon fields in QCD, as well as the search for new particles at LHC.

We present results of a perturbative QCD analysis of deep inelastic measurements of both the deuteron and proton structure functions. We evaluate the theoretical uncertainty associated with nuclear effects in the deuteron, and we extract simultaneously the isospin dependence of (i) the higher twists terms, (ii) the ratio of the longitudinal to transverse cross sections, $R={\sigma }_L/{\sigma }_T,$ and (iii) the ratio of the neutron to proton structure functions, $F_2^n{/F}_2^p.$ The extraction of the latter, in particular, has been at the center of an intense debate. Its accurate determination is crucial both theoretically and for the interpretation of the more precise neutrino experiments including the newly planned high intensity 50 GeV proton synchrotron.