The phase transition from hadronic to quark matter may take place already during the early post-bounce stage of core collapse supernovae when matter is still hot and lepton rich. If the phase transition is of first order and exhibits a barrier, the formation of the new phase occurs via the nucleation of droplets. We investigate the thermal nucleation of a quark phase in supernova matter and calculate its rate for a wide range of physical parameters. We show that the formation of the first droplet of a quark phase might be very fast and therefore the phase transition to quark matter could play an important role in the mechanism and dynamics of supernova explosions.

We investigate the relative size of various twist-3 quark-gluon correlation functions relevant to single transverse spin asymmetries (SSAs) in a quark-diquark model of the nucleon. We calculate the quark-gluon correlation function $T_{q,F}(x,x)$ that is responsible for the gluonic pole contribution to the SSAs, as well as $T_{q,F}(0,x)$ and $T_{\Delta q,F}(0,x)$ responsible for the fermionic pole contributions. We find in both cases of a scalar diquark and an axial-vector diquark that at the first nontrivial order only the $T_{q,F}(x,x)$ is finite while all other quark-gluon correlation functions vanish. Using the same model, we evaluate quark Sivers function and discuss its relation to the $T_{q,F}(x,x)$. We also discuss the implication of our finding to the phenomenological studies of the SSAs.

We show that the nucleon spectrum in a hard-wall anti–de Sitter/QCD model can be improved by use of a relatively large IR cutoff. All of the spin-$1/2$ nucleon masses listed in the Particle Data Group can be fit quite well within 11%. The average error is remarkably only 4.66%.

A sterile neutrino with mass of several keV is a well-motivated dark-matter candidate, and it can also explain the observed velocities of pulsars via anisotropic emission of sterile neutrinos from a cooling neutron star. We discuss the interactions of such relic particles with matter and comment on the prospects of future direct detection experiments. A relic sterile neutrino can interact, via sterile–active mixing, with matter fermions by means of electroweak currents, with the final state containing a relativistic active neutrino. The recoil momentum impacted onto a matter fermion is determined by the sterile neutrino mass and is enough to ionize atoms and flip the spins of nuclei. While this suggests a possibility of direct experimental detection, we calculate the rates and show that building a realistic detector of the required size would be a daunting challenge.

The associated production of neutral Higgs bosons with the ${\mathrm{Z}}^0$ gauge boson (${\mathrm{h}}^0{\mathrm{Z}}^0$, ${\mathrm{H}}^0{\mathrm{Z}}^0$) is investigated in the context of the future linear colliders, such as the ILC and CLIC, within the general two-Higgs-doublet model (2HDM). We compute the corresponding cross section for the processes ${\mathrm{e}}^{+}{\mathrm{e}}^{-}\to {\mathrm{Z}}^0{\mathrm{h}}^0/{\mathrm{Z}}^0{\mathrm{H}}^0$ at one-loop, including the full set of corrections at $\mathcal{O}({\alpha }_{ew}^3)$ together with the leading $\mathcal{O}({\alpha }_{ew}^4)$ terms, in full consistency with the available theoretical and phenomenological constraints. We find that the wave-function corrections to the external Higgs fields are the dominant source of the quantum effects, which turn out to be large and negative (e.g., $\delta \sigma /\sigma \sim -20\%/-60\%$) in all the $\sqrt{s}$ range, and located predominantly in the region around $\tan \beta \sim 1$ and moderate values of the parameter ${\lambda }_5$ (being ${\lambda }_5<0$). This behavior can be ultimately traced back to the enhancement potential of the triple Higgs-boson self-couplings, a trademark feature of the 2HDM with no counterpart in the Higgs sector of the minimal supersymmetric standard model. Even under this substantial depletion of the one-loop-corrected signal (which is also highly distinctive with respect to the SM expectation for ${\mathrm{e}}^{+}{\mathrm{e}}^{-}\to {\mathrm{Z}}^0\mathrm{H}$), the predicted Higgs-strahlung rates comfortably reach a few tens of femtobarn, which means barely $\sim {10}^3–{10}^4$ events per $500{\mathrm{fb}}^{-1}$ of integrated luminosity. Because of their great complementarity, we argue that the combined analysis of the Higgs-strahlung events (${\mathrm{h}}^0{\mathrm{Z}}^0$, ${\mathrm{H}}^0{\mathrm{Z}}^0$) and the previously computed one-loop Higgs-pair production processes (${\mathrm{H}}^0{\mathrm{A}}^0$) could be instrumental to probe the structure of the Higgs sector at future linac facilities.

Decay rates of unpolarized top quarks into longitudinally and transversally polarized $W$ bosons are calculated to second order in the strong coupling constant ${\alpha }_s$. Including the finite bottom quark mass and electroweak effects, the standard model predictions for the $W$-boson helicity fractions are ${\mathcal{F}}_L=0.687(5)$, ${\mathcal{F}}_{+}=0.0017(1)$, and ${\mathcal{F}}_{-}=0.311(5)$.

We introduce an extension of a variationally optimized perturbation method, by combining it with renormalization group properties in a straightforward (perturbative) form. This leads to a very transparent and efficient procedure, with a clear improvement of the nonperturbative results with respect to previous similar variational approaches. This is illustrated here by deriving optimized results for the mass gap of the $O(2N)$ Gross-Neveu model, compared with the exactly known results for arbitrary $N$. At large $N$, the exact result is reproduced already at the very first order of the modified perturbation using this procedure. For arbitrary values of $N$, using the original perturbative information only known at two-loop order, we obtain a controllable percent accuracy or less, for any $N$ value, as compared with the exactly known result for the mass gap from the thermodynamical Bethe Ansatz. The procedure is very general and can be extended straightforwardly to any renormalizable Lagrangian model, being systematically improvable provided that a knowledge of enough perturbative orders of the relevant quantities is available.

We study quasinormal modes and scattering properties via calculation of the $S$ matrix for scalar and electromagnetic fields propagating in the background of spherically symmetric and axially symmetric traversable Lorentzian wormholes of a generic shape. Such wormholes are described by the general Morris-Thorne ansatz. The properties of quasinormal ringing and scattering are shown to be determined by the behavior of the wormhole’s shape function $b(r)$ and shift factor $\Phi (r)$ near the throat. In particular, wormholes with the shape function $b(r)$, such that $b^{\prime }(r)\approx 1$, have very long-lived quasinormal modes in the spectrum. We have proved that the axially symmetric traversable Lorentzian wormholes, unlike black holes and other compact rotating objects, do not allow for superradiance. As a by-product we have shown that the 6th order WKB formula used for scattering problems of black or wormholes gives quite high accuracy and thus can be used for quite accurate calculations of the Hawking radiation processes around various black holes.

We consider slow-roll inflation for a single scalar field with an arbitrary potential and an arbitrary nonminimal coupling to the Gauss-Bonnet term. By introducing a combined hierarchy of Hubble and Gauss-Bonnet flow functions, we analytically derive the power spectra of scalar and tensor perturbations. The standard consistency relation between the tensor-to-scalar ratio and the spectral index of tensor perturbations is broken. We apply this formalism to a specific model with a monomial potential and an inverse monomial Gauss-Bonnet coupling and constrain it by the 7-year Wilkinson Microwave Anisotropy Probe data. The Gauss-Bonnet term with a positive (or negative) coupling may lead to a reduction (or enhancement) of the tensor-to-scalar ratio and hence may revive the quartic potential ruled out by recent cosmological data.

We point out that there are regions in the minimal supersymmetric standard model (MSSM) parameter space which successfully provide a dark matter (DM) annihilation explanation for observed $e^{+}$ excess (e.g., PAMELA), while still remaining in agreement with all other data sets. Such regions (e.g., the uplifted Higgs region) can realize an enhanced neutralino DM annihilation dominantly into leptons via a Breit-Wigner resonance through the $CP$-odd Higgs channel. Such regions can give the proper thermal relic DM abundance, and the DM annihilation products are compatible with current antiproton and gamma ray observations. This scenario can succeed without introducing any additional degrees of freedom beyond those already in the MSSM.

Yang-Mills theories with a gauge group $\mathrm{SU}(N_c\ne 3)$ and quark matter in the fundamental representation share many properties with the theory of strong interactions, QCD with $N_c=3$. We show that, for $N_c$ even and in the confinement phase, the gluonic average of the quark determinant is independent of the boundary conditions, periodic or antiperiodic ones. We then argue that a Fermi sphere of quarks can only exist under extreme conditions when the center symmetry is spontaneously broken and color is liberated. Our findings are supported by lattice gauge simulations for $N_c=2–5$ and are illustrated by means of a simple quark model.

For the first time, a systematic analysis of the high energy behavior of total and diffractive proton-proton cross sections is performed within the Reggeon field theory framework, based on the resummation of all significant contributions of enhanced Pomeron diagrams to all orders with respect to the triple-Pomeron coupling. The importance of different classes of enhanced graphs is investigated, and it is demonstrated that absorptive corrections due to “net”-like enhanced diagrams and due to Pomeron “loops” are both significant and none of those classes can be neglected at high energies. A comparison with other approaches based on partial resummations of enhanced diagrams is performed. In particular, important differences are found concerning the predicted high energy behavior of total and single high mass diffraction proton-proton cross sections, with our values of ${\sigma }_{pp}^{\mathrm{tot}}$ at $\sqrt{s}=14\mathrm{TeV}$ being some 25%–40% higher and with the energy rise of ${\sigma }_{\mathrm{HM}}^{\mathrm{SD}}$ saturating well below the LHC energy. The main causes for those differences are analyzed and explained.

We determine the prospects for finding dark matter at the Tevatron and LHC through the production of exotic fourth-generation mirror quarks $T^{\prime }$ that decay through $T^{\prime }\to tX$, where $X$ is dark matter. The resulting signal of $t\overline{t}+{\mathrm{E̸}}_T$ has not previously been considered in searches for fourth-generation quarks, but there are both general and specific dark matter motivations for this signal, and with slight modifications, this analysis applies to any scenario where invisible particles are produced in association with top quarks. Current direct and indirect bounds on such exotic quarks restrict their masses to be between 300 and 600 GeV, and the dark matter’s mass may be anywhere below $m_{T^{\prime }}$. We simulate the signal and main backgrounds with MadGraph/MadEvent-Pythia-PGS4. For the Tevatron, we find that an integrated luminosity of $20{\mathrm{fb}}^{-1}$ will allow $3\sigma$ discovery up to $m_{T^{\prime }}=400\mathrm{GeV}$ and 95% exclusion up to $m_{T^{\prime }}=455\mathrm{GeV}$. For the 10 TeV LHC with $300{\mathrm{pb}}^{-1}$, the discovery and exclusion sensitivities rise to 490 GeV and 600 GeV. These scenarios are therefore among the most promising for dark matter at colliders. Perhaps most interestingly, we find that dark matter models that can explain results from the DAMA, CDMS, and CoGeNT collaborations can be tested with high statistical significance using data already collected at the Tevatron and have extraordinarily promising implications for early runs of the LHC.

We present a phenomenological analysis of the $\cos 2\varphi$ asymmetry recently measured by the COMPASS and HERMES collaborations in unpolarized semi-inclusive deep inelastic scattering. In the kinematical regimes explored by these experiments the asymmetry arises from transverse-spin and intrinsic transverse-momentum effects. We consider the leading-twist contribution, related to the so-called Boer-Mulders transverse-polarization distribution $h_1^{\perp }(x,k_T^2)$, and the twist-4 Cahn contribution, involving unpolarized transverse-momentum distribution functions. We show that a reasonably good fit of the preliminary data sets from COMPASS and HERMES is achieved with a Boer-Mulders function consistent with the main theoretical expectations. Our conclusion is that the COMPASS and HERMES measurements represent the first experimental evidence of the Boer-Mulders effect in SIDIS.

We consider the black hole solutions of five-dimensional gravity with a Gauss-Bonnet term in the bulk and an induced gravity term on a 2-brane of codimension 2. Applying the Kerr-Schild method we derive additional solutions which include charge and angular momentum. To improve our understanding of this geometry we study the geodesic structure of such spacetimes.

We investigate a holographic superconductor that admits an analytic treatment near the phase transition. In the dual $3+1$-dimensional field theory, the phase transition occurs when a scalar operator of scaling dimension two gets a vacuum expectation value. We calculate current-current correlation functions along with the speed of second sound near the critical temperature. We also make some remarks about critical exponents. An analytic treatment is possible because an underlying Heun equation describing the zero mode of the phase transition has a polynomial solution. Amusingly, the treatment here may generalize for an order parameter with any integer spin, and we propose a Lagrangian for a spin-two holographic superconductor.

We investigate motion of test particles in exact spacetimes with an expanding impulsive gravitational wave which propagates in a Minkowski, a de Sitter, or an anti-de Sitter universe. Using the continuous form of these metrics we derive explicit junction conditions and simple refraction formulas for null, timelike, and spacelike geodesics crossing a general impulse of this type. In particular, we present a detailed geometrical description of the motion of test particles in a special class of axially symmetric spacetimes in which the impulse is generated by a snapped cosmic string.