Gluonic pole matrix elements explain the appearance of single spin asymmetries (SSA) in high-energy scattering processes. They involve a combination of operators which are odd under time reversal (T-odd). Such matrix elements appear in principle both for parton distribution functions and parton fragmentation functions. We show that for parton fragmentation functions, these gluonic pole matrix elements vanish as a consequence of the analytic structure of scattering amplitudes in quantum chromodynamics. This result is important in the study of the universality of transverse-momentum-dependent (TMD) fragmentation functions.

We employ a conformal mapping to explore the thermodynamics of strongly interacting matter at finite values of the baryon chemical potential $\mu$. This method allows us to identify the singularity corresponding to the critical point of a second-order phase transition at finite $\mu$, given information only at $\mu =0$. The scheme is potentially useful for computing thermodynamic properties of strongly interacting hot and dense matter in lattice gauge theory. The technique is illustrated by an application to a chiral effective model.

A theory of exponential modified gravity which explains both early-time inflation and late-time acceleration, in a unified way, is proposed. The theory successfully passes the local tests and fulfills the cosmological bounds and, remarkably, the corresponding inflationary era is proven to be unstable. Numerical investigation of its late-time evolution leads to the conclusion that the corresponding dark energy epoch is not distinguishable from the one for the $\Lambda \mathrm{CDM}$ model. Several versions of this exponential gravity, sharing similar properties, are formulated. It is also shown that this theory is nonsingular, being protected against the formation of finite-time future singularities. As a result, the corresponding future universe evolution asymptotically tends, in a smooth way, to de Sitter space, which turns out to be the final attractor of the system.

Non-Abelian vortices are topologically stable objects in the color-flavor locked phase of dense QCD. We derive a dual Lagrangian starting with the Ginzburg-Landau effective Lagrangian for the color-flavor locked phase, and obtain topological interactions of non-Abelian vortices with quasiparticles such as $\mathrm{U}(1{)}_{\mathrm{B}}$ Nambu-Goldstone bosons (phonons) and massive gluons. We find that the phonons couple to the translational zero modes of the vortices while the gluons couple to their orientational zero modes in the internal space.

The fermionic condensate is investigated in a ($2+1$)-dimensional conical spacetime in the presence of a circular boundary and a magnetic flux. It is assumed that on the boundary the fermionic field obeys the MIT bag boundary condition. For irregular modes, we consider a special case of boundary conditions at the cone apex, when the MIT bag boundary condition is imposed at a finite radius, which is then taken to zero. The fermionic condensate is a periodic function of the magnetic flux with the period equal to the flux quantum. For both exterior and interior regions, the fermionic condensate is decomposed into boundary-free and boundary-induced parts. Two integral representations are given for the boundary-free part for arbitrary values of the opening angle of the cone and magnetic flux. At distances from the boundary larger than the Compton wavelength of the fermion particle, the condensate decays exponentially, with the decay rate depending on the opening angle of the cone. If the ratio of the magnetic flux to the flux quantum is not a half-integer number for a massless field the boundary-free part in the fermionic condensate vanishes, whereas the boundary-induced part is negative. For half-integer values of the ratio of the magnetic flux to the flux quantum, the irregular mode gives a nonzero contribution to the fermionic condensate in the boundary-free conical space.

We study conservative finite-mass corrections to the motion of a particle in a bound (eccentric) strong-field orbit around a Schwarzschild black hole. We assume the particle’s mass $\mu$ is much smaller than the black hole mass $M$, and explore post-geodesic corrections of $O(\mu /M)$. Our analysis uses numerical data from a recently developed code that outputs the Lorenz-gauge gravitational self-force (GSF) acting on the particle along the eccentric geodesic. First, we calculate the $O(\mu /M)$ conservative correction to the periastron advance of the orbit, as a function of the (gauge-dependent) semilatus rectum and eccentricity. A gauge-invariant description of the GSF precession effect is made possible in the circular-orbit limit, where we express the correction to the periastron advance as a function of the invariant azimuthal frequency. We compare this relation with results from fully nonlinear numerical-relativistic simulations. In order to obtain a gauge-invariant measure of the GSF effect for fully eccentric orbits, we introduce a suitable generalization of Detweiler’s circular-orbit “redshift” invariant. We compute the $O(\mu /M)$ conservative correction to this invariant, expressed as a function of the two invariant frequencies that parametrize the orbit. Our results are in good agreement with results from post-Newtonian calculations in the weak-field regime, as we shall report elsewhere. The results of our study can inform the development of analytical models for the dynamics of strongly gravitating binaries. They also provide an accurate benchmark for future numerical-relativistic simulations.

We investigate the non-Gaussianities of inflation driven by a single scalar field coupling nonminimally to the Einstein Gravity. We assume that the form of the scalar field is very general with an arbitrary sound speed. For convenience, we take the subclass that the nonminimal coupling term is linear to the Ricci scalar $R$. We define a parameter $\mu \equiv {ϵ}_h/{ϵ}_{\theta }$, where ${ϵ}_h$ and ${ϵ}_{\theta }$ are two kinds of slow-roll parameters, and obtain the dependence of the shape of the 3-point correlation function on $\mu$. We also show the estimator $F_{\mathrm{NL}}$ in the equilateral limit. Finally, based on numerical calculations, we present the non-Gaussianities of nonminimal coupling chaotic inflation as an explicit example.

We put constraints on asymmetric dark matter candidates with spin-dependent interactions based on the simple existence of white dwarfs and neutron stars in globular clusters. For a wide range of the parameters (WIMP mass and WIMP-nucleon cross section), weakly interacting massive particles (WIMPs) can be trapped in progenitors in large numbers and once the original star collapses to a white dwarf or a neutron star, these WIMPs might self-gravitate and eventually collapse forming a mini–black hole that eventually destroys the star. We impose constraints competitive to direct dark matter search experiments, for WIMPs with masses down to the TeV scale.

We explore dark matter mechanisms that can simultaneously explain the galactic 511 keV gamma rays observed by INTEGRAL/SPI, the DAMA/LIBRA annual modulation, and the excess of low-recoil dark matter candidates observed by CoGeNT. It requires three nearly degenerate states of dark matter in the 4–7 GeV mass range, with splittings, respectively, of order MeV and a few keV. The top two states have the small mass gap and transitions between them, either exothermic or endothermic, and can account for direct detections. Decays from one of the top states to the ground state produce low-energy positrons in the Galaxy whose associated 511 keV gamma rays are seen by INTEGRAL. This decay can happen spontaneously, if the excited state is metastable (longer lived than the age of the Universe), or it can be triggered by inelastic scattering of the metastable states into the shorter-lived ones. We focus on a simple model where the dark matter is a triplet of an $SU(2)$ hidden sector gauge symmetry, broken at the scale of a few GeV, giving masses of order $\lesssim 1\mathrm{GeV}$ to the dark gauge bosons, which mix kinetically with the standard model hypercharge. The purely decaying scenario can give the observed angular dependence of the 511 keV signal with no positron diffusion, while the inelastic scattering mechanism requires transport of the positrons over distances $\sim 1\mathrm{kpc}$ before annihilating. We note that an x-ray line of several keV in energy, due to single-photon decays involving the top dark matter states, could provide an additional component to the diffuse x-ray background. The model is testable by proposed low-energy fixed-target experiments.

Quantum fields in compact stars can be amplified due to a semiclassical instability, which may affect the structure of relativistic stars. We show that a classical counterpart to this instability occurs in exactly the same region of the parameter space. For negative coupling parameter $\xi$, the instability is related to the well-known “spontaneous scalarization” effect. The plausible end state is a static, asymptotically flat configuration with a nonzero scalar field, which is compatible with weak-field experiments and energetically favored over stellar solutions in general relativity. For $\xi >0$ the new configurations are energetically disfavored, and the end state of the instability remains an open issue. The vacuum instability may lead to new experimental opportunities to probe the nature of vacuum energy via astrophysical observations of compact stars.

A numerical error requires a refit of the resonance parameters. The qualitative statements and the conclusions of the paper remain unchanged.

We discuss the prospects for setting limits on or discovering spin-1 $Z^{\prime }$ bosons using early LHC data at 7 TeV. Our results are based on the narrow width approximation in which the leptonic Drell-Yan $Z^{\prime }$ boson production cross section only depends on the $Z^{\prime }$ boson mass together with two parameters $c_u$ and $c_d$. We carefully discuss the experimental cuts that should be applied and tabulate the theoretical next-to-next-to-leading order corrections which must be included. Using these results the approach then provides a safe, convenient, and unbiased way of comparing experiment to theoretical models which avoids any built-in model-dependent assumptions. We apply the method to three classes of perturbative $Z^{\prime }$ boson benchmark models: $E_6$ models, left-right symmetric models, and sequential standard models. We generalize each class of model in terms of mixing angles which continuously parametrize linear combinations of pairs of generators and lead to distinctive orbits in the $c_u-c_d$ plane. We also apply this method to the strongly coupled four-site benchmark model in which two $Z^{\prime }$ bosons are predicted. By comparing the experimental limits or discovery bands to the theoretical predictions on the $c_u-c_d$ plane, we show that the LHC at 7 TeV with integrated luminosity of $500{\mathrm{pb}}^{-1}$ will greatly improve on current Tevatron mass limits for the benchmark models. If a $Z^{\prime }$ is discovered our results show that measurement of the mass and cross section will provide a powerful discriminator between the benchmark models using this approach.

We investigate the spectrum and wave functions of ${\overline{q}}^{\prime }{q}^{\prime }$ bound states for heavy fourth generation quarks ($q^{\prime }$) that have a very small mixing with the three observed generations of standard model quarks. Such bound states come with different color, spin and flavor quantum numbers. Since the fourth generation Yukawa coupling, ${\lambda }_{q^{\prime }}$, is large we include all perturbative corrections to the potential between the heavy quark and antiquark of order ${\lambda }_{q^{\prime }}^2{N}_c/16{\pi }^2$ where $N_c$ is the number of colors, as well as relativistic corrections suppressed by $(v/c{)}^2$. We find that the lightest fourth generation quark masses for which a bound state exists for color octet states. For the color singlet states, which always have a bound state, we analyze the influence that the Higgs couplings have on the size and binding energy of the bound states.

QCD sum rules involving mixed inverse moment integration kernels are used in order to determine the running charm-quark mass in the $\overline{\mathrm{MS}}$ scheme. Both the high and the low energy expansion of the vector current correlator are involved in this determination. The optimal integration kernel turns out to be of the form $p(s)=1-(s_0/s{)}^2$, where $s_0$ is the onset of perturbative QCD. This kernel enhances the contribution of the well known narrow resonances, and reduces the impact of the data in the range $s\simeq 20–25{\mathrm{GeV}}^2$. This feature leads to a substantial reduction in the sensitivity of the results to changes in $s_0$, as well as to a much reduced impact of the experimental uncertainties in the higher resonance region. The value obtained for the charm-quark mass in the $\overline{\mathrm{MS}}$ scheme at a scale of 3 GeV is ${\overline{m}}_c(3\mathrm{GeV})=987\pm 9\mathrm{MeV}$, where the error includes all sources of uncertainties added in quadrature.

We demonstrate that in the back-to-back kinematics the production of four jets in the collision of two partons is suppressed in the leading log approximation of pQCD, compared to the Êhard processes involving the collision of four partons. We derive the basic equation for four-jet production in QCD in terms of the convolution of generalized two-parton distributions of colliding hadrons in the momentum space representation. Our derivation leads to geometrical approach in the impact parameter space close to that suggested within the parton model and used before to describe the four-jet production. We develop the independent parton approximation to the light-cone wave function of the proton. Comparison with the CDF and D0 data shows that the independent parton approximation to the light-cone wave function of the proton is insufficient to explain the data. We argue that the data indicate the presence of significant multiparton correlations in the light-cone wave functions of colliding protons.

We compute the zero point energy in a spherically symmetric background distorted at high energy as predicted by Gravity’s Rainbow. In this context we setup a Sturm-Liouville problem with the cosmological constant considered as the associated eigenvalue. The eigenvalue equation is a reformulation of the Wheeler-DeWitt equation. With the help of a canonical decomposition, we find that the relevant contribution to one loop is given by the graviton quantum fluctuations around the given background. By means of a variational approach based on Gaussian trial functionals, we find that the ordinary divergences can here be handled by an appropriate choice of the rainbow’s functions, in contrast to what happens in other conventional approaches. A final discussion on the connection of our result with the observed cosmological constant is also reported.

The magnetic inelastic dark matter (MiDM) model, in which dark matter inelastically scatters off nuclei through a magnetic dipole interaction, has previously been shown to reconcile the DAMA/LIBRA annual modulation signal with null results from other experiments. In this work, we explore the unique directional detection signature of MiDM. After the dark matter scatters into its excited state, it decays with a lifetime of order $1\mu \mathrm{s}$ and emits a photon with energy $\sim 100\mathrm{keV}$. Both the nuclear recoil and the corresponding emitted photon can be detected by studying delayed coincidence events. The recoil track and velocity of the excited state can be reconstructed from the nuclear interaction vertex and the photon event vertex. The angular distribution of the WIMP recoil tracks is sharply peaked and modulates daily. It is therefore possible to observe the directional modulation of WIMP-nucleon scattering without a large-volume gaseous directional detection experiment. Furthermore, current experiments such as XENON100 can immediately measure this directional modulation and constrain the MiDM parameter space with an exposure of a few thousand $\mathrm{kg}·\mathrm{day}$.

Magnetic flares and induced oscillations of magnetars (supermagnetized neutron stars) are promising sources of gravitational waves (GWs). We suggest that the GW emission, if any, would last longer than the observed x-ray quasiperiodic oscillations (X-QPOs), calling for longer-term GW analyses lasting a day to months, compared to current searches’ durations. Like the pulsar timing, the oscillation frequency would also evolve with time because of the decay or reconfiguration of the magnetic field, which is crucial for the GW detection. With the observed GW frequency and its time-derivatives, we can probe the interior magnetic field strength of $\sim {10}^{16}\mathrm{G}$ and its evolution to open a new GW asteroseismology with the next generation interferometers like the advanced laser interferometer gravitational wave observatory, the advanced Virgo gravitational wave detector at the European Gravitational Observatory, the Large-scale cryogenic gravitational wave telescope, and the Einstein telescope.

We calculate the rate for thermal production of axions via scattering of quarks and gluons in the primordial quark-gluon plasma. To obtain a finite result in a gauge-invariant way that is consistent to leading order in the strong gauge coupling, we use systematic field theoretical methods such as hard thermal loop resummation and the Braaten-Yuan prescription. The thermally produced yield, the decoupling temperature, and the density parameter are computed for axions with a mass below 10 meV. In this regime, with a Peccei-Quinn scale above $6\times {10}^8\mathrm{GeV}$, the associated axion population can still be relativistic today and can coexist with the axion cold dark matter condensate.

We propose a scheme that allows to analytically determine the three elementary cross sections and connect the solutions to the relative sign between the proton and the neutron spin scattering amplitudes once the measurements of total event rate from three appropriate targets become available. In this way it is thus possible to extract the maximum information on the supersymmetric parameter space obtainable from direct detection experiments, in the case that the dark matter particle is the lightest neutralino. Our scheme is based on suitably normalized forms of the isospin momentum dependent structure functions entering in the spin-dependent elastic neutralino-nucleus cross section. We compare these functions with the commonly used ones and discuss their advantages: in particular, these allow in the spin-dependent cross section to factorize the particle physics degrees of freedom from the momentum transfer dependent nuclear structure functions as it happens in the spin-independent cross section with the nuclear form factor.