One of the most tantalizing results from the Wilkinson Microwave Anisotropy Probe (WMAP) experiment is the suggestion that the power at large scales is anomalously low when compared to the prediction of the “standard” $\Lambda$ cold dark matter (CDM) model. The same anomaly, although with somewhat larger uncertainty, was also previously noted in the COBE data. In this work we discuss possible alternate models that give better fits on large scales and apply a model-comparison technique to select amongst them. We find that models with a cutoff in the power spectrum at large scales are indeed preferred by data, but only by a factor of 3.6, at most, in the likelihood ratio, corresponding to about “1.6σ” if interpreted in the traditional manner. Using the same technique, we have also examined the possibility of a systematic error in the measurement or prediction of the large-scale power. Ignoring other evidence that the large-scale modes are properly measured and predicted, we find this possibility somewhat more likely, with roughly a 2.75σ evidence.

We consider cosmological models with a scalar field with equation of state $w>~1$ that contract towards a big crunch singularity, as in recent cyclic and ekpyrotic scenarios. We show that chaotic mixmaster oscillations due to anisotropy and curvature are suppressed, and the contraction is described by a homogeneous and isotropic Friedmann equation if $w>\mathrm{}1.\mathrm{}$ We generalize the results to theories where the scalar field couples to p forms and show that there exists a finite value of w, depending on the p-forms, such that chaotic oscillations are suppressed. We show that $Z_2$ orbifold compactification also contributes to suppressing chaotic behavior. In particular, chaos is avoided in contracting heterotic M-theory models if $w>\mathrm{}1\mathrm{}$ at the crunch.

We study the evolution of the cosmological perturbations after inflation in curvaton models where the nonrelativistic curvaton decays into both radiation and a cold dark matter component. We calculate the primordial curvature and correlated isocurvature perturbations inherited by the radiation and cold dark matter after the curvaton has decayed. We give the transfer coefficient in terms of the initial curvaton density relative to the curvaton decay rate.

We study the effect of a helicity component of a primordial magnetic field on the tensor part of the cosmic microwave background temperature anisotropies and polarization. We give analytical approximations for the tensor contributions induced by helicity, discussing their amplitude and spectral index in dependence of the power spectrum of the primordial magnetic field. We find that an helical magnetic field creates a parity odd component of gravity waves inducing parity odd polarization signals. However, only if the magnetic field is close to scale invariant and if its helical part is close to maximal, the effect is sufficiently large to be observable. We also discuss the implications of causality on the magnetic field spectrum.

It is shown that embedding of flipped $\mathrm{SU}\left(5\right)\mathrm{}$ in a five-dimensional $\mathrm{SO}\left(10\right)\mathrm{}$ enables exact unification of the gauge coupling constants. The demand for unification uniquely determines both the compactification scale and the cutoff scale. These are found to be $M_C\approx 5.5\times {10}^{14}\mathrm{GeV},$ and $M_{*}\approx 1.0\times {10}^{17}\mathrm{GeV},$ respectively. The theory explains the absence of $d=5\mathrm{}$ proton-decay operators through the implementation of the missing partner mechanism. On the other hand, the presence of $d=6\mathrm{}$ proton-decay operators points towards the bulk localization of the first and second families of matter fields.

We discuss the measurement of top-squark and bottom-squark mixing angles in high energy $e^{+}{e}^{-}$ reactions at CERN LEP-II and the proposed linear collider. We focus on off-diagonal production of one lighter and one heavier squark. In the context of the light bottom squark scenario, we show that existing data from LEP-II should show definitive evidence for the heavier bottom squark provided that its mass $m_{b_2}<~120\mathrm{GeV}.$

The results of a high-statistics study of scalar and pseudoscalar meson propagators in quenched lattice QCD are presented. For two values of lattice spacing, $\beta =5.7\mathrm{}\left(a\approx .18\mathrm{fm}\right)$ and 5.9 $\left(a\approx .12\mathrm{fm}\right),$ we probe the light quark mass region using clover improved Wilson fermions with the modified quenched approximation pole-shifting ansatz to treat the exceptional configuration problem. The quenched chiral loop parameters $m_0$ and ${\alpha }_{\Phi }$ are determined from a study of the pseudoscalar hairpin correlator. From a global fit to the meson correlators, estimates are obtained for the relevant chiral Lagrangian parameters, including the Leutwyler parameters $L_5$ and $L_8.$ Using the parameters obtained from the singlet and nonsinglet pseudoscalar correlators, the quenched chiral loop (QCL) effect in the nonsinglet scalar meson correlator is studied. By removing this QCL effect from the lattice correlator, we obtain the mass and decay constant of the ground state scalar, isovector meson $a_0.$

Generalized parton distributions at large x are studied in the perturbative QCD approach. As $\overrightarrow{x}1$ and at finite t, there is no t dependence for the GPDs which means that the active quark is at the center of the transverse space. We also obtain the power behavior $H_q^{\pi }(x,\xi ,t)\sim (1\mathrm{}-{x)}^2/(1\mathrm{}-{\xi }^2)$ for the pion, $H_q(x,\xi ,t)\sim (1\mathrm{}-{x)}^3/(1\mathrm{}-{\xi }^2{)}^2$ and $E_q(x,\xi ,t)\sim (1\mathrm{}-{x)}^5/(1\mathrm{}-{\xi }^2{)}^{3}f\left(\xi \right)$ for the nucleon, where $f\left(\xi \right)$ represents the additional dependence on $\xi .$

The strong and electromagnetic amplitudes are analyzed on the basis of the measurements of $J/\psi ,\psi \mathrm{}\left(2S\right)\mathrm{}\to 1^{-}{0}^{-}$ in $e^{+}{e}^{-}$ experiments. The currently available experimental information is revised with the inclusion of the contribution from $e^{+}{e}^{-}\to {\gamma }^{*}\to 1^{-}{0}^{-}.$ The study shows that a large phase around $-90°$ between the strong and electromagnetic amplitudes could not be ruled out by the experimental data for $\psi \mathrm{}\left(2S\right).$

We investigate some processes of the associated production of a neutral top-pion ${\Pi }_t^0$ with a pair of fermions ${(e}^{+}{e}^{-}\to f\overline{f}{\Pi }_t^0)$ in the context of top-color-assisted technicolor (TC2) theory in the future $e^{+}{e}^{-}$ colliders. The studies show that the largest cross sections of the processes $e^{+}{e}^{-}\to f^{\prime }\overline{f^{\prime }}{\Pi }_t^0{(f}^{\prime }=u,d,c,s,\mu ,\tau )$ could only reach the level of 0.01 fb; we can hardly detect a neutral top-pion through these processes. For the processes $e^{+}{e}^{-}\to e^{+}{e}^{-}{\Pi }_t^0,$ $e^{+}{e}^{-}\to t\overline{t}{\Pi }_t^0,$ and $e^{+}{e}^{-}\to b\overline{b}{\Pi }_t^0,$ the cross sections of these processes are at the level of a few fb for the favorable parameters, and a few tens, even hundreds, of neutral top-pion events can be produced at future $e^{+}{e}^{-}$ colliders each year through these processes. With the clean background of the flavor-changing $t\overline{c}$ channel, the top-pion events can possibly be detected at the planned high luminosity $e^{+}{e}^{-}$ colliders. Therefore, such neutral top-pion production processes provide a useful way to detect a neutral top-pion and test the TC2 model directly.

An analytic method of smearing link variables in lattice QCD is proposed and tested. The differentiability of the smearing scheme with respect to the link variables permits the use of modern Monte Carlo updating methods based on molecular dynamics evolution for gauge-field actions constructed using such smeared links. In examining the smeared mean plaquette and the static quark-antiquark potential, no degradation in effectiveness is observed as compared to link smearing methods currently in use, although an increased sensitivity to the smearing parameter is found.

We show that measurements of the proton’s polarization in $e^{+}{e}^{-}\to p\overline{p}$ strongly discriminate between analytic forms of models which fit the proton form factors in the spacelike region. In particular, the single-spin asymmetry normal to the scattering plane measures the relative phase difference between the timelike $G_E$ and $G_M$ form factors. The expected proton polarization in the timelike region is large, of the order of several tens of percent.

We investigate polarized parton distribution functions (PDFs) and their uncertainties by using world data on the spin asymmetry $A_1.$ The uncertainties of polarized PDFs are estimated by the Hessian method. The up and down valence-quark distributions are determined well. However, the antiquark distributions have large uncertainties at this stage, and it is particularly difficult to fix the gluon distribution. The ${\chi }^2$ analysis produces a positively polarized gluon distribution, but even $\Delta g\left(x\right)=0\mathrm{}$ could be allowed according to our uncertainty estimation. In comparison with the previous Asymmetry Analysis Collaboration parametrization, accurate SLAC-E155 proton data are added to the analysis. We find that the E155 data improve the determination of polarized PDFs, especially the polarized antiquark distributions. In addition, gluon-distribution uncertainties are reduced due to the correlation with the antiquark distributions. We also show the global analysis results with the condition $\Delta g\left(x\right)=0\mathrm{}$ at the initial scale, $Q^2=1\mathrm{}{\mathrm{GeV}}^2,$ for clarifying the error correlation effects with the gluon distribution.

Programs that calculate observables in quantum chromodynamics at next-to-leading order typically generate events that consist of partons rather than hadrons—and just a few partons at that. These programs would be much more useful if the few partons were turned into parton showers, which could be given to one of the Monte Carlo event generators to produce hadron showers. In a previous paper, we have seen how to generate parton showers related to the final state collinear singularities of the perturbative calculation for the example of $e^{+}{+e}^{-}\to 3$ jets. This paper discusses the treatment of the soft singularities.

Programs that calculate observables in quantum chromodynamics at next-to-leading order typically suffer from the problem that, when considered as event generators, the events generated consist of partons rather than hadrons and just a few partons at that. Thus the events generated are completely unrealistic. These programs would be much more useful if the few partons were turned into parton showers, in the style of standard Monte Carlo event generators. Then the parton showers could be given to one of the Monte Carlo event generators to produce hadron showers. We show how to generate parton showers related to the final state collinear singularities of the next-to-leading order perturbative calculation for the example of $e^{+}{+e}^{-}\to 3\mathrm{jets}.$ The soft singularities are left for a separate publication.

We examine Killing spinor equations of the general eleven-dimensional pp-wave backgrounds, which contain a scalar ${H(x}^m{,x}^{-})$ in the metric and a three-form $\xi {(x}^m{,x}^{-})$ in the flux. Considering nonharmonic extra Killing spinors, we show that, if the backgrounds admit at least one extra Killing spinor in addition to the standard 16 Killing spinors, they can be reduced to the form with ${H=A}_{\mathrm{mn}}{(x}^{-}{)x}^m{x}^n$ and $\xi {(x}^{-})$ modulo coordinate transformations. We further examine the cases in which the extra Killing spinor is characterized by a set of Cartan matrices. The superisometry algebras of the resulting backgrounds are also derived.

We investigate possible extensions of the $\mathrm{}(2+1)\mathrm{}$-dimensional ${\mathrm{CP}}^{N-1}$ model to noncommutative space. Up to the leading nontrivial order of $1/N,$ we prove that the model restricted to the left fundamental representation of the gauge group is renormalizable and does not have dangerous infrared divergences. In contrast, if the basic field $\phi$ transforms in accord with the adjoint representation, infrared singularities are present in the two-point function of the auxiliary gauge field and also in the leading correction to the self-energy of the $\phi$ field. These infrared divergences may produce nonintegrable singularities leading at higher orders to a breakdown of the $1/N$ expansion. Gauge invariance of the renormalization procedure is also discussed.

We present two new classes of magnetic brane solutions in Einstein-Maxwell-Gauss-Bonnet gravity with a negative cosmological constant. The first class of solutions yields an $\mathrm{}(n+1\mathrm{})\mathrm{}$-dimensional spacetime with a longitudinal magnetic field generated by a static magnetic brane. We also generalize this solution to the case of spinning magnetic branes with one or more rotation parameters. We find that these solutions have no curvature singularity and no horizons, but have a conic geometry. In these spacetimes, when all the rotation parameters are zero, the electric field vanishes, and therefore the brane has no net electric charge. For the spinning brane, when one or more rotation parameters are nonzero, the brane has a net electric charge which is proportional to the magnitude of the rotation parameter. The second class of solutions yields a spacetime with an angular magnetic field. These solutions have no curvature singularity, no horizon, and no conical singularity. Again we find that the net electric charge of the branes in these spacetimes is proportional to the magnitude of the velocity of the brane. Finally, we use the counterterm method in the Gauss-Bonnet gravity and compute the conserved quantities of these spacetimes.

As was recently pointed out by Cadoni, a certain class of two-dimensional gravitational theories will exhibit a (black hole) thermodynamic behavior that is reminiscent of a free field theory. In the current Rapid Communication, a direct correspondence is established between these two-dimensional models and the strongly curved regime of (arbitrary-dimensional) anti–de Sitter gravity. On this basis, we go on to speculatively argue that two-dimensional gravity may ultimately be utilized for identifying and perhaps even understanding holographic dualities.

An approximation method to study the properties of a small black hole located on the TeV brane in the Randall-Sundrum type I scenario is presented. The method enables us to find the form of the metric close to the matter distribution when its asymptotic form is given. The short range solution is found as an expansion in the ratio between the Schwarzschild radius of the black hole and the curvature length of the bulk. Long range properties are introduced using the linearized gravity solution as an asymptotic boundary condition. The solution is found up to first order. It is valid in the region close to the horizon but is not valid on the horizon. The regularity of the horizon is still under study.