We present a high precision calculation of chargino and neutralino pair production at $e^{+}{e}^{-}$ colliders. Within the minimal supersymmetric standard model, the full one-loop and higher order QED corrections are included. Special care has been taken in the definition of the Lagrangian input parameters. Furthermore, the proper inclusion of QED corrections and the separation of weak and QED corrections are discussed. We show numerical results for total cross sections, as well as forward-backward and left-right asymmetries for the SPS1a’ scenario as proposed in the SPA (supersymmetry parameter analysis) project. The complete corrections are about 10% and in some cases even larger, in particular, for ${\tilde{\chi }}_i^0{\tilde{\chi }}_j^0$ production with sizable Higgsino components. These corrections have to be taken into account in a high precision analysis.

We study the resummation of large logarithmic perturbative corrections to the partonic cross sections relevant for the process $pp\to hX$ at high transverse momentum of the hadron $h$. These corrections arise near the threshold for the partonic reaction and are associated with soft-gluon emission. We perform the resummation to next-to-leading logarithmic accuracy. We present numerical results for the fixed-target regime and find enhancements over the next-to-leading order cross section, which significantly improve the agreement between theoretical predictions and data. We also apply the resummation for Relativistic Heavy-Ion Collider kinematics and find that subleading terms appear to play a rather important role here.

It is suggested that the resonance $\psi (3770)$ may contain a sizeable ($O(10\%)$ in terms of the probability weight factor) four-quark component with the up- and down-quarks and antiquarks in addition to the $c\overline{c}$ pair, which component in itself has a substantial part with isospin $I=1$. Furthermore such a four-quark part of the wave function should also affect the properties of the ${\psi }^{\prime }$ charmonium resonance through the $\psi (3770)-{\psi }^{\prime }$ mixing previously considered in the literature. It is argued that an admixture of extra light quark pairs can explain a possible discrepancy between the theoretical expectations and the recent data on the non-$D\overline{D}$ decay width of the $\psi (3770)$ and the ratio of the yield of charged and neutral $D$ meson pairs in its decays, as well as on the extra rate of the ${\psi }^{\prime }$ direct decay into light hadrons and the rate of the decay ${\psi }^{\prime }\to {\pi }^{0}J/\psi$. It is further argued that the suggested four-quark component of the wave function of the $\psi (3770)$ should give rise to a measurable rate for the decays $\psi (3770)\to \eta J/\psi$ and $\psi (3770)\to {\pi }^{0}J/\psi$.

Exclusive decays of ${\eta }_c$ into vector meson pairs ($\varphi \varphi$, $\rho \rho$, $K^{*}{\overline{K}}^{*}$, $\omega \omega$, $\omega \varphi$) are investigated in the framework of the ${}^{3}P_0$ quark-creation model. While these decay widths are zero in the leading order of ${\alpha }_s$ in the perturbative QCD scheme, the ${}^{3}P_0$ quark-creation mechanism gives results comparable with experimental data. We also calculate the rates of $\Gamma ({\eta }_c(2S)\to VV)/\Gamma ({\eta }_c\to VV)$. The results show different behavior from those decay modes allowed by perturbative QCD in leading order.

We study the weak decay of the neutral pion to a neutrino-antineutrino pair, ${\pi }^0\to \nu \overline{\nu }$, in the Skyrme model. In baryon-free-space the process is forbidden by helicity while in a dense baryonic medium, the process becomes possible already to leading order in $G_F$ due to the break-down of Lorentz symmetry in the background medium.

We study the scaling regime of hadron-(anti)hadron annihilation into a deeply virtual photon and a real photon, $H\overline{H}\to {\gamma }^{*}\gamma$, and backward virtual Compton scattering, ${\gamma }^{*}H\to H\gamma$. We advocate that there is a kinematical region where the scattering amplitude factorizes into a short-distance matrix element and a long-distance dominated object: a transition distribution amplitude which describes the hadron to photon transition.

We discuss the effective action for weak $G_2$ compactifications of M-theory. The presence of fluxes acts as a source for the axions and drives the Freund-Rubin parameter to zero. The result is a stable nonsupersymmetric vacuum with a negative cosmological constant. We also give the superpotential which generates the effective potential and discuss a simple model which aims to incorporate the effects of supersymmetry breaking by the gauge sector.

The null infinity limit of the gravitational energy-momentum and energy flux determined by the covariant Hamiltonian quasilocal expressions is evaluated using the Newman-Penrose spin coefficients. The reference contribution is considered by three different embedding approaches. All of them give the expected Bondi energy and energy flux.

We investigate the response of traversable wormholes to external perturbations through finding their characteristic frequencies and time-domain profiles. The considered solution describes traversable wormholes between the branes in the two brane Randall-Sundrum model and was previously found within Einstein gravity with a conformally coupled scalar field. The evolution of perturbations of a wormhole is similar to that of a black hole and represents damped oscillations (ringing) at intermediately late times, which are suppressed by power-law tails (proportional to $t^{-2}$ for monopole perturbations) at asymptotically late times.

We compute numerically the quasinormal modes of Kerr-Newman black holes in the scalar case, for which the perturbation equations are separable. Then we study different approximations to decouple electromagnetic and gravitational perturbations of the Kerr-Newman metric, computing the corresponding quasinormal modes. Our results suggest that the Teukolsky-like equation derived by Dudley and Finley gives a good approximation to the dynamics of a rotating charged black hole for $Q\lesssim M/2$. Though insufficient to deal with Kerr-Newman based models of elementary particles, the Dudley-Finley equation should be adequate for astrophysical applications.

We construct an approximate solution which describes the gravitational emission from a naked singularity formed by the gravitational collapse of a cylindrical thick shell composed of dust. The assumed situation is that the collapsing speed of the dust is very large. In this situation, the metric variables are obtained approximately by a kind of linear perturbation analysis in the background Morgan solution which describes the motion of cylindrical null dust. The most important problem in this study is what boundary conditions for metric and matter variables should be imposed at the naked singularity. We find a boundary condition that all the metric and matter variables are everywhere finite at least up to the first order approximation. This implies that the spacetime singularity formed by this high-speed dust collapse is very similar to that formed by the null dust and the final singularity will be a conical one. Weyl curvature is completely released from the collapsed dust.

We investigate the Dirac quasinormal modes (QNMs) of a Schwarzschild black hole using continued fraction and Hill-determinant approaches. For large angular quantum number, we find that the fundamental quasinormal frequencies become evenly spaced and the spacing is given by ${\omega }_{\lambda +1}-{\omega }_{\lambda }=0.38490-0.00000i$, where $\lambda =\pm (l+1/2)$ ($l$ is the angular quantum number). We show that the angular quantum number has a surprising effect of increasing real part but almost does not affect imaginary part of the quasinormal frequencies, especially for the lowest lying mode. We also find that the spacing for imaginary part of the quasinormal frequencies at high overtones is equidistant and equals to $-i/4M$, as it takes place for scalar, electromagnetic and gravitational perturbations.

We extend Choptuik’s scaling phenomenon found in general relativistic critical gravitational collapse of a massless scalar field to higher dimensions. We find that in the range $4\le D\le 11$ the behavior is qualitatively similar to that discovered by Choptuik. In each dimension we obtain numerically the universal numbers associated with the critical collapse: the scaling exponent $\gamma$ and the echoing period $\Delta$. The behavior of these numbers with increasing dimension seems to indicate that $\gamma$ reaches a maximum and $\Delta$ a minimum value around $11\le D\le 13$. These results and their relation to the black hole–black string system are discussed.

We propose a model which produces dark energy perturbations large enough to explain the lack of power seen at the quadrupole scale in the cosmic microwave background. If the dark energy is frozen from horizon exit during inflation until dark energy domination, then it is not possible to have perturbations in the dark energy which are large enough. We propose using a tachyonic amplification mechanism to overcome this. The dark energy is taken to be a complex scalar field, where the radial field has a Mexican hat potential. During inflation, the radial component is trapped near the maximum of its potential. At the end of inflation, it rolls down to the minimum. The dark energy today is taken to be a pseudo-Nambu-Goldstone boson. The perturbations generated during inflation are amplified by the rolling of the radial field. We also examine the use of the variable decay mechanism in order to generate an anticorrelation between the dark energy perturbations and the curvature perturbation. We show that using this mechanism then constrains the properties of the dark energy and its evolution from redshift one until today.

We propose a new method for identifying new physics imprints on present observational data in cosmology whereby signatures of string theory are clearly distinguished from imprints of possible features on the inflaton potential. Our method relies on the cross-correlations spectra of cosmic shear from large scale structure (LSS) with the cosmic microwave background (CMB) temperature anisotropies and $E$-mode polarization, by using the following properties: inflationary cosmology provides only one source term for all CMB spectra and LSS which highly constrains any deviations from the standard predictions; string theory can add new noninflationary channels to the source of perturbations as well as modify clustering properties at large scales. Discrepancies in the source terms of correlations and clustering properties provide the evidence for new physics. Models of single-field inflation with a feature are disfavored even with present data. Upcoming Wilkinson microwave anisotropy probe (WMAP) results and future data from weak lensing of LSS will further improve our ability to probe new physics in this manner and could open the first direct window to string theory.

Spin-dependent weakly interacting massive particle (WIMP) searches have traditionally presented results within an odd group approximation and by suppressing one of the spin-dependent interaction cross sections. We here elaborate on a model-independent analysis in which spin-dependent interactions with both protons and neutrons are simultaneously considered. Within this approach, equivalent current limits on the WIMP-nucleon interaction at WIMP mass of $50\mathrm{GeV}/c^2$ are either ${\sigma }_p\le 0.7\mathrm{pb}$, ${\sigma }_n\le 0.2\mathrm{pb}$ or $|a_p|\le 0.4$, $|a_n|\le 0.7$ depending on the choice of cross section or coupling strength representation. These limits become less restrictive for either larger or smaller masses; they are less restrictive than those from the traditional odd group approximation regardless of WIMP mass. Combinations of experimental results are seen to produce significantly more restrictive limits than those obtained from any single experiment. Experiments traditionally considered spin-independent are moreover found to severely limit the spin-dependent phase space. The extension of this analysis to the case of positive signal experiments is explored.

We study the slow-roll regime of two-field inflation, in which the two scalar fields are also coupled through their kinetic terms. Such Lagrangians are motivated by particle physics and by scalar-tensor theories studied in the Einstein frame. We compute the power spectra of adiabatic and isocurvature perturbations on large scales to first order in the slow-roll parameters. We discuss the relevance of the extra coupling terms for the amplitude and indexes of the power spectra. Beyond the consistency condition which involves the amplitude of gravitational waves, additional relations may be found in particular models based on such Lagrangians: as an example, we find an additional general consistency condition in implicit form for Brans-Dicke theory in the Einstein frame.

We propose a novel method for detecting gravitational waves (GW), where a light signal emitted from a distant star interacts with a local (also distant) GW source and travels towards the Earth, where it is detected. While traveling in the field of the GW, the light acquires specific phase modulation (which we account in the eikonal approximation). This phase modulation can be considered as a coherent spreading of the given initial photons energy over a set of satellite lines, spaced at the frequency of GW (from quantum point of view it is multigraviton absorption and emission processes). This coherent state of photons with the energy distributed among the set of equidistant lines, can be analyzed and identified on Earth either by passing the signal through a Fabry-Perot filter or by monitoring the intensity-intensity correlations at different times.

We investigate pion superfluidity and its effect on meson properties and equation of state at finite temperature and isospin and baryon densities in the frame of a standard flavor SU(2) NJL model. In mean field approximation to quarks and random phase approximation to mesons, the critical isospin chemical potential for pion superfluidity is exactly the pion mass in the vacuum, and corresponding to the isospin symmetry spontaneous breaking, there is in the pion superfluidity phase a Goldstone mode which is the linear combination of the normal sigma and charged pion modes. We calculate numerically the gap equations for the chiral and pion condensates, the phase diagrams, the meson spectra, and the equation of state, and compare them with that obtained in other effective models. The competitions between pion superfluidity and color superconductivity at finite baryon density and between pion and kaon superfluidity at finite strangeness density in flavor SU(3) NJL model are briefly discussed.

In this note we calculate the form of electroweak corrections in deconstructed Higgsless models for the case of a fermion whose weak properties arise from two adjacent $SU(2)$ groups on the deconstructed lattice. We show that, as recently proposed in the continuum, it is possible for the value of the electroweak parameter $\alpha S$ to be small in such a model. In addition, by working in the deconstructed limit, we may directly evaluate the size of off-$Z$-pole electroweak corrections arising from the exchange of Kaluza-Klein modes; this has not been studied in the continuum. The size of these corrections is summarized by the electroweak parameter $\alpha \delta$. In one-site delocalized Higgsless models with small values of $\alpha S$, we show that the amount of delocalization is bounded from above, and must be less than 25% at 95% C.L. We discuss the relation of these calculations to our previous calculations in deconstructed Higgsless models, and to models of extended technicolor. We present numerical results for a four-site model, illustrating our analytic calculations.