We provide a comprehensive, up-to-date analysis of possible new physics contributions to the mass difference $\Delta M_D$ in $D^0\mathrm{\text{−}}{\overline{D}}^0$ mixing. We consider the most general low-energy effective Hamiltonian and include leading-order QCD running of effective operators. We then explore an extensive list of possible new physics models that can generate these operators, which we organize as including extra fermions, extra gauge bosons, extra scalars, extra space dimensions and extra symmetries. For each model we place restrictions on the allowed parameter space using the recent evidence for observation of $D$ meson mixing. In many scenarios, we find strong constraints that surpass those from other search techniques and provide an important test of flavor-changing neutral currents in the up-quark sector. We also review the recent BABAR and Belle findings, and describe the current status of the standard model predictions of $D^0\mathrm{\text{−}}{\overline{D}}^0$ mixing.

Neutralino annihilations in the Sun to weak boson and top-quark pairs lead to high-energy neutrinos that can be detected by the IceCube and KM3 experiments in the search for neutralino dark matter. We calculate the neutrino signals from real and virtual $WW$, $ZZ$, $Zh$, and $t\overline{t}$ production and decays, accounting for the spin dependences of the matrix elements, which can have important influences on the neutrino energy spectra. We take into account neutrino propagation including neutrino oscillations, matter-resonance, absorption, and ${\nu }_{\tau }$ regeneration effects in the Sun and evaluate the neutrino flux at the Earth. We concentrate on the compelling focus point (FP) region of the supergravity model that reproduces the observed dark matter relic density. For the FP region, the lightest neutralino has a large bino-Higgsino mixture that leads to a high neutrino flux and the spin-dependent neutralino capture rate in the Sun is enhanced by ${10}^3$ over the spin-independent rate. For the standard estimate of neutralino captures, the muon signal rates in IceCube are identifiable over the atmospheric neutrino background for neutralino masses above $M_Z$ up to 400 GeV.

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 $h$, when the initial protons are longitudinally polarized. We perform the resummation to next-to-leading logarithmic accuracy. We present numerical results for center-of-mass energies $\sqrt{S}=19.4\mathrm{GeV}$, relevant for comparisons to data from the Fermilab E704 experiment, and $\sqrt{S}=62.4\mathrm{GeV}$, where preliminary data from RHIC have recently become available. We find significant enhancements of the spin-dependent cross sections, but a decrease of the double-spin asymmetry for the process. This effect is less pronounced at the higher energy.

Some unusual features observed in hadronic collisions at high energies can be understood assuming that gluons in hadrons are located within small spots occupying only about 10% of the hadrons’ area. Such a conjecture about the presence of two scales in hadrons helps to explain the following: why diffractive gluon radiation is so suppressed; why the triple-Pomeron coupling shows no $t$ dependence; why total hadronic cross sections rise so slowly with energy; why diffraction cones shrink so slowly, and why ${\alpha }_{\mathbb{P}}^{\prime }\ll {\alpha }_{\mathbb{R}}^{\prime }$; why the transition from hard to soft regimes in the structure functions occurs at rather large $Q^2$; why the observed Cronin effect at collider energies is so weak; why hard reactions sensitive to primordial parton motion (direct photon, Drell-Yan dileptons, heavy flavors, back-to-back dihadrons, seagull effect, etc.) demand such a large transverse momenta of the projectile partons, which is not explained by next-to-leading order calculations; why the onset of nuclear shadowing for gluons is so delayed compared to quarks; and why shadowing is so weak.

We present a systematic study of exclusive charmless nonleptonic two-body $B$ decays including axial-vector mesons in the final state. We calculate branching ratios of $B\to PA$, $VA$, and $AA$ decays, where $A$, $V$, and $P$ denote an axial vector, a vector, and a pseudoscalar meson, respectively. We assume a naive factorization hypothesis and use the improved version of the nonrelativistic Isgur-Scora-Grinstein-Wise quark model for form factors in $B\to A$ transitions. We include contributions that arise from the effective $\Delta B=1$ weak Hamiltonian $H_{\mathrm{eff}}$. The respective factorized amplitudes of these decays are explicitly shown and their penguin contributions are classified. We find that decays $B^{-}\to a_1^0{\pi }^{-}$, ${\overline{B}}^0\to a_1^{\pm }{\pi }^{\mp }$, $B^{-}\to a_1^{-}{\overline{K}}^0$, ${\overline{B}}^0\to a_1^{+}{K}^{-}$, ${\overline{B}}^0\to f_1{\overline{K}}^0$, $B^{-}\to f_1{K}^{-}$, $B^{-}\to K_1^{-}(1400){\eta }^{(\prime )}$, $B^{-}\to b_1^{-}{\overline{K}}^0$, and ${\overline{B}}^0\to b_1^{+}{\pi }^{-}(K^{-})$ have branching ratios of the order of ${10}^{-5}$. We also study the dependence of branching ratios for $B\to K_{1}P(V,A)$ decays [$K_1=K_1(1270)$, $K_1(1400)$] with respect to the mixing angle between $K_{1A}$ and $K_{1B}$.

We reproduce the deep inelastic scattering measurements of the proton structure function at high energy from the dipole model in momentum space. To model the dipole-proton forward scattering amplitude, we use the knowledge of asymptotic solutions of the Balitsky-Kovchegov equation, describing high-energy QCD in the presence of saturation effects. The comparison of our results with previous analysis in coordinate space and possible extensions of our approach are discussed.

In Lorentz-violating electrodynamics a steady current (and similarly a static charge) generates both static magnetic and electric fields. These induced fields, acting on interfering particles, change the interference pattern. We find that particle interference experiments are sensitive to small Lorentz-violating effects, and thus they can be used to improve current bounds on some Lorentz-violating parameters.

We study interactions of unparticles $\mathcal{U}$ of dimension $d_{\mathcal{U}}$ due to Georgi with standard model (SM) fields through effective operators. The unparticles describe the low energy physics of a nontrivial scale invariant sector. Since unparticles come from beyond the SM physics, it is plausible that they transform as a singlet under the SM gauge group. This helps tremendously in limiting possible interactions. We analyze interactions of scalar $\mathcal{U}$, vector ${\mathcal{U}}^{\mu }$, and spinor ${\mathcal{U}}^s$ unparticles with SM fields and derivatives up to dimension four. Using these operators, we discuss different features of producing unparticles at an $e^{+}{e}^{-}$ collider and other phenomenologies. It is possible to distinguish different unparticles produced at an $e^{+}{e}^{-}$ collider by looking at various distributions of production cross sections.

We present a large new family of Wilson loop operators in $\mathcal{N}=4$ supersymmetric Yang-Mills theory. For an arbitrary curve on the three dimensional sphere one can add certain scalar couplings to the Wilson loop so it preserves at least two supercharges. Some previously known loops, notably the $1/2$ BPS circle, belong to this class, but we point out many more special cases which were not known before and could provide further tests of the AdS/CFT correspondence.

This paper extends the study, initiated by Rozowsky and Thorn, of gauge fields in interaction with Dirac fields living on separated parallel 1-branes. In a light-cone description, replacing static point sources by 1-brane sources allows $p^{+}$ conservation to be maintained in their presence, which simplifies the light-cone quantization procedure. Here we calculate on-shell branion scattering amplitudes through one loop in light-cone gauge, and thereby resolve a puzzling ambiguity encountered in the earlier off-shell calculations. We confirm that infrared divergences cancel in properly defined scattering probabilities. This work lays the groundwork for the incorporation of 1-brane sources in the light-cone worldsheet formalism.

The forthcoming Planck experiment will provide high sensitivity polarization measurements that will allow us to further tighten the $f_{\mathrm{NL}}$ bounds from the temperature data. Monte Carlo simulations of non-Gaussian cosmic microwave background maps have been used as a fundamental tool to characterize non-Gaussian signatures in the data, as they allow us to calibrate any statistical estimators and understand the effect of systematics, foregrounds and other contaminants. We describe an algorithm to generate high-angular resolution simulations of non-Gaussian cosmic microwave background maps in temperature and polarization. We consider non-Gaussianities of the local type, for which the level of non-Gaussianity is defined by the dimensionless parameter, $f_{\mathrm{NL}}$. We then apply the temperature and polarization fast cubic statistics recently developed by Yadav et al. to a set of non-Gaussian temperature and polarization simulations. We compare our results to theoretical expectations based on a Fisher matrix analysis, test the unbiasedness of the estimator, and study the dependence of the error bars on $f_{\mathrm{NL}}$. All our results are in very good agreement with theoretical predictions, thus confirming the reliability of both the simulation algorithm and the fast cubic temperature and polarization estimator.

We examine the stability of the nonextremal D1-D5-P black hole solutions. In particular, we look for the appearance of a superradiant instability for the spinning black holes but we find no evidence of such an instability. We compare this situation with that for the smooth soliton geometries, which were recently observed to suffer from an ergoregion instability, and consider the implications for the fuzzball proposal.

Coset methods are used to construct the action describing the dynamics associated with the spontaneous breaking of the Poincaré symmetries of $D$ dimensional space-time due to the embedding of a $p$-brane with codimension $N=D-p-1$. The resulting world volume action is an $ISO(1,p+N)$ invariant generalization of the Nambu-Goto action in $d=p+1$ dimensional space-time. Analogous results are obtained for an anti-de Sitter (AdS) $p$-brane with codimension $N$ embedded in $D$ dimensional AdS space, yielding an $SO(2,p+N)$ invariant version of the Nambu-Goto action in $d=p+1$ dimensional space-time. Attention is focused on a supersymmetric extension of the $D=6$ Minkowski space case with an embedded $p=3$ brane; a particular realization of which is provided by a non-BPS vortex. Here both the Nambu-Goto-Akulov-Volkov action and its dual tensor form are presented.

A possible electric-magnetic duality suggests that the confinement of non-Abelian electric charges manifests itself as a perturbative quantum effect for the dual magnetic charges. Motivated by this possibility, we study vacuum fluctuations around a non-Abelian monopole-antimonopole pair treated as point objects with charges $g=\pm n/2$ ($n=1,2,\dots$), and placed on the antipodes of a three sphere of radius $R$. We explicitly find all the fluctuation modes by linearizing and solving the Yang-Mills equations about this background field on a three sphere. We recover, generalize, and extend earlier results, including those on the stability analysis of non-Abelian magnetic monopoles. We find that for $g\ge 1$ monopoles there is an unstable mode that tends to squeeze magnetic flux in the angular directions. We sum the vacuum energy contributions of the fluctuation modes for the $g=1/2$ case and find oscillatory dependence on the cutoff scale. Subject to certain assumptions, we find that the contribution of the fluctuation modes to the quantum zero-point energy grows as $\sim -R^{-2/3}$ and hence decays more slowly than the classical $-R^{-1}$ Coulomb potential for large $R$. However, the growth of the zero-point energy does not agree with the linear growth expected if the monopoles are confined.

We discuss the cosmological evolution of a braneworld in five-dimensional Gauss-Bonnet gravity. Our discussion allows the fifth (bulk) dimension to be spacelike as well as timelike. The resulting equations of motion have the form of a cubic equation in the $(H^2,(\rho +\sigma {)}^2)$ plane, where $\sigma$ is the brane tension and $\rho$ is the matter density. This allows us to conduct a comprehensive pictorial analysis of cosmological evolution for the Gauss-Bonnet brane. The many interesting properties of this braneworld include the possibility of accelerated expansion at late times. For a finite region in parameter space the accelerated expansion can be phantomlike so that $w<-1$. At late times, this branch approaches de Sitter space ($w=-1$) and avoids the big-rip singularities usually present in phantom models. For a timelike extra dimension the Gauss-Bonnet brane can bounce and avoid the initial singularity.

We consider Green’s functions associated to a scalar field propagating on a curved, ultrastatic background, in the presence of modified dispersion relations. The usual proper-time DeWitt-Schwinger procedure to obtain a series representation of Green’s functions is doomed to failure because of higher order spatial derivatives in the Klein-Gordon operator. We show how to overcome this difficulty by considering a preferred frame, associated to a unit timelike vector. With respect to this frame, we can express Green’s functions as an integral over all frequencies of a space-dependent function. The latter can be expanded in momentum space, as a series with geometric coefficients similar to the DeWitt-Schwinger ones. By integrating over all frequencies, we finally find the expansion of Green’s function up to four derivatives of the metric tensor. The relation with the proper-time formalism is also discussed.

Recoil “kicks” induced by gravitational radiation are expected in the inspiral and merger of black holes. Recently the numerical relativity community has begun to measure the significant kicks found when both unequal masses and spins are considered. Because understanding the cause and magnitude of each component of this kick may be complicated in inspiral simulations, we consider these effects in the context of a simple test problem. We study recoils from collisions of binaries with initially head-on trajectories, starting with the simplest case of equal masses with no spin and then adding spin and varying the mass ratio, both separately and jointly. We find spin-induced recoils to be significant relative to unequal-mass recoils even in head-on configurations. Additionally, it appears that the scaling of transverse kicks with spins is consistent with post-Newtonian theory, even though the kick is generated in the nonlinear merger interaction, where post-Newtonian theory should not apply. This suggests that a simple heuristic description might be effective in the estimation of spin kicks.

We construct the metric of new multi-black-hole configurations on a $d$-dimensional cylinder ${\mathbb{R}}^{d-1}\times S^1$, in the limit of small total mass (or equivalently in the limit of a large cylinder). These solutions are valid to first order in the total mass and describe configurations with several small black holes located at different points along the circle direction of the cylinder. We explain that a static configuration of black holes is required to be in equilibrium such that the external force on each black hole is zero, and we examine the resulting conditions. The first-order corrected thermodynamics of the solutions is obtained and a Newtonian interpretation of it is given. We then study the consequences of the multi-black-hole configurations for the phase structure of static Kaluza-Klein black holes and show that our new solutions imply continuous nonuniqueness in the phase diagram. The new multi-black-hole configurations raise the question of existence of new nonuniform black strings. Finally, a further analysis of the three-black-hole configuration suggests the possibility of a new class of static lumpy black holes in Kaluza-Klein space.

We investigate the relic density $n_{\chi }$ of nonrelativistic long-lived or stable particles $\chi$ in nonstandard cosmological scenarios. We calculate the relic abundance starting from arbitrary initial temperatures of the radiation-dominated epoch, and derive the lower bound on the initial temperature $T_0\ge m_{\chi }/23$, assuming that thermally produced $\chi$ particles account for the dark matter energy density in the Universe; this bound holds for all $\chi$ annihilation cross sections. We also investigate cosmological scenarios with modified expansion rate. Even in this case an approximate formula similar to the standard one is capable of predicting the final relic abundance correctly. Choosing the $\chi$ annihilation cross section such that the observed cold dark matter abundance is reproduced in standard cosmology, we constrain possible modifications of the expansion rate at $T\sim m_{\chi }/20$, well before big bang nucleosynthesis.