We study the phenomenon of spontaneous breaking of rotational symmetry in the rotating solutions of two types of baby Skyrme models. In the first, the domain is a two-sphere, and in the other, the Skyrmions are confined to the interior of a unit disk. Numerical full-field results show that when the angular momentum of the Skyrmions increases above a certain critical value, the rotational symmetry of the solutions is broken and the minimal-energy configurations become less symmetric. We propose a possible mechanism as to why spontaneous breaking of rotational symmetry is present in the rotating solutions of these models, while it is not observed in the “usual” baby Skyrme model. Our results might be relevant for a qualitative understanding of the nonspherical deformation of excited nucleons with high orbital angular momentum.

We study quasielastic rescattering effects in ${\overline{B}}_{u,d,s}\to DP,\overline{D}P$ decays, where $P$ is a light pseudoscalar. The updated measurements of ${\overline{B}}_{u,d}\to DP$ decays are used to extract the effective Wilson coefficients $a_1^{\mathrm{eff}}\simeq 0.90$ and $a_2^{\mathrm{eff}}\simeq 0.23$, three strong phases $\delta \simeq 56°$, $\theta \simeq 18°$, and $\sigma \simeq -104°$, and the mixing angle $\tau \simeq 7°$. This information is used to predict rates of 19 ${\overline{B}}_s\to DP$ and ${\overline{B}}_{u,d,s}\to \overline{D}P$ decay modes, including modes of interests in the $\gamma /{\varphi }_3$ program. Many decay rates are found to be enhanced. In particular, the ${\overline{B}}_s\to D^0{K}^0$ rate is predicted to be $7\times {10}^{-4}$, which could be measured soon. The rescattering effects on the corresponding ${\overline{B}}_{u,d,s}\to \overline{D}P,DP$ amplitude ratios $r_B$ and $r_{B_s}$, and the relative strong phases ${\delta }_B$ and ${\delta }_{B_s}$ are studied. Although the decay rates are enhanced in most cases, $r_{B,B_s}$ values are similar to factorization expectation.

We study the supersymmetric model with $D_4\times Z_2$ lepton flavor symmetry. We evaluate soft supersymmetry breaking terms, i.e., soft slepton masses and A-terms, which are predicted in the $D_4$ flavor model. We consider constraints due to experiments of flavor-changing neutral current processes.

We study the properties of potential new $Z^{\prime }$ gauge bosons produced through the Drell-Yan mechanism at the Large Hadron Collider (LHC). Our analysis is performed using a fully differential next-to-leading-order QCD calculation with spin correlations, interference effects, and experimental acceptances included. We examine the distinguishability of different models and the feasibility of extracting general coupling information with statistical, residual scale, and current parton distribution function error estimates included. We extend a previous parametrization of $Z^{\prime }$ couplings to include parity-violating coupling combinations and introduce a convenient technique for simulating new gauge bosons on-peak using the concept of basis models. We illustrate our procedure using several example $Z^{\prime }$ models. We find that one can extract reliably four combinations of generation-independent quark and lepton couplings in our analysis. For a $Z^{\prime }$ mass of 1.5 TeV, one can determine coupling information very well assuming $100{\mathrm{fb}}^{-1}$ of integrated luminosity, and a precise measurement becomes possible with $1{\mathrm{ab}}^{-1}$ at the super-LHC (SLHC). For a 3 TeV mass, a reasonable determination requires the SLHC.

One of the important features of the littlest Higgs model with $T$ parity, called the LHT model, is that it introduces the mirror fermions, which are the $T$-parity partners of the standard model fermions. In this paper, we discuss production of the mirror quark associated with a mirror neutrino via $e\gamma$ and $ep$ collisions. We find that, in a wide range of the parameter space, the mirror quark can be copiously produced at the International Linear $e^{+}{e}^{-}$ Collider and $ep$ collider (THERA) experiments. The production rates of certain signal events, which are related the main two-body decay modes of the mirror quark, are also calculated.

We study the combined effects of both strong and electroweak dimension six effective operators on flavor changing top quark physics at the CERN LHC. Analytic expressions for the cross sections and decay widths of several flavor changing processes will be presented, as well as an analysis of the feasibility of their observation at the LHC.

We calculate chiral corrections to the semileptonic vector and axial quark coupling constants using a manifestly Lorentz covariant chiral quark approach up to order $\mathcal{O}(p^4)$ in the two- and three-flavor pictures. These couplings are then used in the evaluation of the corresponding couplings which govern the semileptonic transitions between octet baryon states. In the calculation of baryon matrix elements we use a general ansatz for the spatial form of the quark wave function, without referring to a specific realization of hadronization and confinement of quarks in baryons. Matching the physical amplitudes calculated within our approach to the model-independent predictions of baryon chiral perturbation theory allows us to deduce a connection between our parameters and those of baryon chiral perturbation theory.

The magnetic moments of heavy ${\Xi }_Q$ baryons containing a single charm or bottom quark are calculated in the framework of the light cone QCD sum rules method. A comparison of our results with the predictions of other approaches, such as relativistic and nonrelativistic quark models, the hypercentral model, chiral perturbation theory, and soliton and skyrmion models, is presented.

We present a complete next-to-leading order calculation for the total cross section for inclusive Higgs pair production via bottom-quark fusion at the CERN Large Hadron Collider in the minimal supersymmetric standard model and the minimal supergravity model. We emphasize the contributions of squark and gluino loops and the decoupling properties of our results for heavy squark and gluino masses. The enhanced couplings of the $b$ quark to the Higgs bosons in supersymmetric models with large $\tan \beta$ yield large next-to-leading order supersymmetry QCD corrections in some regions of parameter space.

The charge asymmetry of $W$ bosons produced in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ is sensitive to the ratio of $d$ and $u$ quark distributions in the range of $x>0.002$ at $Q^2\approx M_W^2$. We propose an analysis technique to directly measure $W$ production charge asymmetry from $W\to e\nu$ events at the Tevatron and show the feasibility for this method using Monte Carlo simulations.

We consider rigid rotating closed strings with spikes in ${\mathrm{AdS}}_5$ dual to certain higher twist operators in $\mathcal{N}=4$ SYM theory. In the limit of large spin when the spikes reach the boundary of ${\mathrm{AdS}}_5$, the solutions with different numbers of spikes are related by conformal transformations, implying that their energy is determined by the same function of the ’t Hooft coupling $f(\lambda )$ that appears in the anomalous dimension of twist 2 operators or in the cusp anomaly. In the limit when the number of spikes goes to infinity, we find an equivalent description in terms of a string moving in an AdS pp-wave background. From the boundary theory point of view, the corresponding description is based on the gauge theory living in a 4d pp-wave space. Then, considering a charge moving at the speed of light, or a null Wilson line, we find that the integrated energy-momentum tensor has a logarithmic UV divergence that we call the “pp-wave anomaly.” The AdS/CFT correspondence implies that, for $\mathcal{N}=4$ SYM, this pp-wave anomaly should have the same value as the cusp anomaly. We verify this at lowest order in SYM perturbation theory. As a side result of our string theory analysis, we find new open string solutions in the Poincare patch of the standard AdS space which end on a lightlike Wilson line and also in two parallel lightlike Wilson lines at the boundary.

We study the mechanism of particle production in the world volume of a probe $\overline{D6}$-brane (or $D6$ with supersymmetry (SUSY) breaking) moving in the background created by a fixed stack of $D6$-branes. We show that this may occur in a regime of parametric resonance when the probe’s motion is nonrelativistic and it moves at large distances from the source branes in low eccentricity orbits. This leads to an exponential growth of the particle number in the probe’s world volume and constitutes an effective mechanism for producing very massive particles. We also analyze the evolution of this system in an expanding universe and how this affects the development of the parametric resonance. We discuss the effects of transverse space compactification on the probe’s motion, showing that it leads to the creation of angular momentum in a similar way to the Affleck-Dine mechanism for baryogenesis. Finally, we describe possible final states of the system and their potential relevance to cosmology.

We show that the gauge-invariant transverse-momentum-dependent (TMD) quark distribution function can be expressed as a sum of all higher-twist collinear parton matrix elements in terms of a transport operator. From such a general expression, we derive the nuclear broadening of the transverse-momentum distribution. Under the maximal two-gluon correlation approximation, in which all higher-twist nuclear multiple parton correlations with the leading nuclear enhancement are given by products of twist-two nucleon parton distributions, we find the nuclear transverse-momentum distribution as a convolution of a Gaussian distribution and the nucleon TMD quark distribution. The width of the Gaussian, or the mean total transverse-momentum broadening squared, is given by the path integral of the quark transport parameter ${\widehat{q}}_F$ which can also be expressed in a gauge-invariant form and is given by the gluon distribution density in the nuclear medium. We further show that contributions from higher-twist nucleon gluon distributions can be resummed under the extended adjoint two-gluon correlation approximation and the nuclear transverse-momentum distribution can be expressed in terms of a transverse-scale-dependent quark transport parameter or gluon distribution density. We extend the study to hot medium and compare to dipole model approximation and $\mathcal{N}=4$ supersymmetric Yang-Mills (SYM) theory in the strong coupling limit. We find that multiple gluon correlations become important in the strongly coupled system such as $\mathcal{N}=4$ SYM plasma.

The space-time symmetry of noncommutative quantum field theories with a deformed quantization is described by the twisted Poincaré algebra, while that of standard commutative quantum field theories is described by the Poincaré algebra. Based on the equivalence of the deformed theory with a commutative field theory, the correspondence between the twisted Poincaré symmetry of the deformed theory and the Poincaré symmetry of a commutative theory is established. As a by-product, we obtain the conserved charge associated with the twisted Poincaré transformation to make the twisted Poincaré symmetry evident in the deformed theory. Our result implies that the equivalence between the commutative theory and the deformed theory holds in a deeper level, i.e., it holds not only in correlation functions but also in (different types of) symmetries.

We model the massive dark object at the center of the Galaxy as a Schwarzschild black hole as well as Janis-Newman-Winicour naked singularities, characterized by the mass and scalar charge parameters, and study gravitational lensing (particularly time delay, magnification centroid, and total magnification) by them. We find that the lensing features are qualitatively similar (though quantitatively different) for Schwarzschild black holes, weakly naked, and marginally strongly naked singularities. However, the lensing characteristics of strongly naked singularities are qualitatively very different from those due to Schwarzschild black holes. The images produced by Schwarzschild black hole lenses and weakly naked and marginally strongly naked singularity lenses always have positive time delays. On the other hand, strongly naked singularity lenses can give rise to images with positive, zero, or negative time delays. In particular, for a large angular source position the direct image (the outermost image on the same side as the source) due to strongly naked singularity lensing always has a negative time delay. We also found that the scalar field decreases the time delay and increases the total magnification of images; this result could have important implications for cosmology. As the Janis-Newman-Winicour metric also describes the exterior gravitational field of a scalar star, naked singularities as well as scalar star lenses, if these exist in nature, will serve as more efficient cosmic telescopes than regular gravitational lenses.

In this paper we calculate $\mathcal{O}({\mu }^4)$ corrections from holonomies in the loop quantum gravity, usually not taken into account. Allowance of the corrections of this kind is equivalent with the choice of the new quatization scheme. Quantization ambiguities in the loop quantum cosmology allow for this additional freedom and presented corrections are consistent with the standard approach. We apply these corrections to the flat Friedmann-Robertson-Walker cosmological model and calculate the modified Friedmann equation. We show that the bounce appears in the models with the standard $\mathcal{O}({\mu }^2)$ quantization scheme and is shifted to the higher energies ${\rho }_{\mathrm{bounce}}=3{\rho }_{\mathrm{c}}$. Also, a pole in the Hubble parameter appears for ${\rho }_{\mathrm{pole}}=\frac{3}{2}{\rho }_{\mathrm{c}}$ corresponding to hyperinflation/deflation phases. This pole represents a curvature singularity at which the scale factor is finite. In this scenario the singularity and bounce coexist. Moreover, we find that an ordinary bouncing solution appears only when quantum corrections in the lowest order are considered. Higher order corrections can lead to nonperturbative effects.

The intermediate and late-time behavior of massive Dirac hair in the static spherically general black hole spacetime is studied. It is revealed that the intermediate asymptotic pattern of decay of massive Dirac spinor hair is dependent on the mass of the field under consideration as well as the multiple number of the wave mode. The long-lived oscillatory tail observed at timelike infinity in the considered background decays slowly as $t^{-5/6}$.

We have considered the holographic large $N_c$ QCD model proposed by Sakai and Sugimoto and evaluated the non-Abelian DBI-action on the $D8$-brane up to $({\alpha }^{\prime }{)}^4$ terms. Restricting to the pion sector, these corrections give rise to four derivative contact terms for the pion field. We derive the Weinberg’s phenemenological Lagrangian. The coefficients of the four derivative terms are determined in terms of $g_{\mathrm{YM}}^2$. The low energy pion-pion scattering amplitudes are evaluated. Numerical results are presented with the choice of $M_{\mathrm{KK}}=0.94\mathrm{GeV}$ and $N_c=11$. The results are compared with the amplitudes calculated using the experimental phase shifts. The agreement with the experimental data is found to be satisfactory.

An improved description of four-pion production in electron-positron annihilation and in $\tau$-lepton decays is presented. The model amplitude is fitted to recent data from BABAR which cover a wide energy range and which were obtained exploiting the radiative return. Predicting $\tau$-decay distributions from $e^{+}{e}^{-}$ data and comparing these predictions with ALEPH and CLEO results, the validity of isospin symmetry is confirmed within the present experimental errors. A good description of two- and three-pion subdistributions is obtained. Special emphasis is put on the predictions for $\omega \pi (\to {\pi }^{+}{\pi }^{-}{\pi }^0)$ in $e^{+}{e}^{-}$ annihilation and in $\tau$ decay. The model amplitude is implemented in the Monte Carlo generator PHOKHARA.