The generalized Gerasimov-Drell-Hearn sum rule is known to be very sensitive to QCD radiative and power corrections. We improve the previously developed QCD-inspired model for the $Q^2$ dependence of the Gerasimov-Drell-Hearn sum rule. We take into account higher order radiative and higher-twist power corrections extracted from precise Jefferson Lab data on the lowest moment of the spin-dependent proton structure function ${\Gamma }_1^p(Q^2)$ and on the Bjorken sum rule ${\Gamma }_1^{p-n}(Q^2)$. By using the singularity-free analytic perturbation theory we demonstrate that the matching point between chiral-like positive-$Q^2$ expansion and QCD operator product $1/Q^2$ expansion for the nucleon spin sum rules can be shifted down to rather low $Q\simeq {\Lambda }_{\mathrm{QCD}}$ leading to a good description of recent proton, neutron, deuteron, and Bjorken sum rule data at all accessible $Q^2$.

The $B_s^0\to J/\psi \varphi$ and $B_s^0\to J/\psi f_0(980)$ decays are analyzed within generalized QCD factorization including all leading-order corrections in ${\alpha }_s$: We point out that the ratio of our calculated widths, $\Gamma (B_s^0\to J/\psi f_0(980)$, $f_0(980)\to {\pi }^{+}{\pi }^{-})/\Gamma (B_s^0\to J/\psi \varphi ,\varphi \to K^{+}{K}^{-})$, strongly indicates that $S$-wave effects in the $f_0(980)$’s daughter pions or kaons cannot be ignored in the extraction of the $B_s-{\overline{B}}_s$ mixing angle, $-2{\beta }_s$, from the $B_s^0\to \varphi J/\psi$ decay amplitudes.

We consider the prospect of lightest neutralino (${\tilde{\chi }}_1^0$) as a dark matter candidate in light of recent interesting observations from the XENON100 and CDMS-II experiments in minimal supergravity framework with large $\tan \beta$ and nonvanishing $A_0$. Within the WMAP satisfied zone, there is a large direct detection reach of lighter ${\tilde{\chi }}_1^0$ in the lighter Higgs boson mediated resonance annihilation domain of the above scenario. It is seen that the heavier Higgs boson plays a dominating role in the ${\tilde{\chi }}_1^0-p$ cross section in the associated zone of parameter space in spite of having a larger mass. Possible LHC signatures are discussed.

We suggested a Monte Carlo approach to simulate a kinetic equilibrium ensemble, and proved the equivalence to the linear equations method on equilibrium. With the convenience of the numerical method, we introduced variable splitting rates representing the details of the dynamics as model parameters which were not considered in previous works. The dependence on model parameters was studied, and it was found that the sea quark flavor asymmetry weakly depends on model parameters. It reflects the statistics principle, contributes the dominant part of the asymmetry, and the effect caused by details of the dynamics is small. We also applied the Monte Carlo approach of the statistical model to predict the theoretical sea quark asymmetries in kaons, octet baryons $\Sigma$, $\Xi$, and $\Delta$ baryons, even in exotic pentaquark states.

We study the dynamics of confinement-deconfinement phase transition in the context of relativistic heavy-ion collisions within the framework of effective models for the Polyakov loop order parameter. We study the formation of $Z(3)$ walls and associated strings in the initial transition from the confining (hadronic) phase to the deconfining [quark-gluon plasma (QGP)] phase via the so-called Kibble mechanism. Essential physics of the Kibble mechanism is contained in a sort of domain structure arising after any phase transition which represents random variation of the order parameter at distances beyond the typical correlation length. We implement this domain structure by using the Polyakov loop effective model with a first order phase transition and confine ourselves with temperature/time ranges so that the first order confinement-deconfinement transition proceeds via bubble nucleation, leading to a well defined domain structure. The formation of $Z(3)$ walls and associated strings results from the coalescence of QGP bubbles expanding in the confining background. We investigate the evolution of the $Z(3)$ wall and string network. We also calculate the energy density fluctuations associated with $Z(3)$ wall network and strings which decay away after the temperature drops below the quark-hadron transition temperature during the expansion of QGP. We discuss evolution of these quantities with changing temperature via Bjorken’s hydrodynamical model and discuss possible experimental signatures resulting from the presence of $Z(3)$ wall network and associate strings.

We study the Polyakov loop and the correlator of two Polyakov loops at finite temperature in the weak-coupling regime. We calculate the Polyakov loop at order $g^4$. The calculation of the correlator of two Polyakov loops is performed at distances shorter than the inverse of the temperature and for electric screening masses larger than the Coulomb potential. In this regime, it is accurate up to order $g^6$. We also evaluate the Polyakov-loop correlator in an effective field theory framework that takes advantage of the hierarchy of energy scales in the problem and makes explicit the bound-state dynamics. In the effective field theory framework, we show that the Polyakov-loop correlator is at leading order in the multipole expansion the sum of a color-singlet and a color-octet quark-antiquark correlator, which are gauge invariant, and compute the corresponding color-singlet and color-octet free energies.

We propose a method for constructing Yukawa terms for noncommutative SO(10) and ${\mathrm{E}}_6$ GUTs when these GUTs are formulated within the enveloping-algebra formalism. The most general noncommutative Yukawa term that we propose contains, at first order in ${\theta }^{\mu \nu }$, the most general Becchi-Rouet-Stora invariant Yukawa contribution whose only dimensionful parameter is the noncommutativity parameter. This noncommutative Yukawa interaction is thus renormalizable at first order in ${\theta }^{\mu \nu }$.

We formulate a Ginsparg-Wilson relation on a fuzzy 2-sphere for matter in the adjoint representation of the gauge group. Because of the Ginsparg-Wilson relation, an index theorem is satisfied. Our formulation is applicable to topologically nontrivial configurations as monopoles. It gives a solid basis for obtaining chiral fermions, which are an important ingredient of the standard model, from matrix model formulations of the superstring theory, such as the IIB matrix model, by considering topological configurations in the extra dimensions. We finally discuss whether this mechanism really works.

We investigate the UV fixed-point structure of the three-dimensional Thirring model by means of the functional renormalization group. We classify all possible 4-fermi interactions compatible with the present chiral and discrete symmetries and calculate the purely fermionic renormalization group flow using a full basis of fermionic four-point functions in the pointlike limit. Our results show that the UV complete (asymptotically safe) Thirring model lies in a two-dimensional coupling plane which reduces to the conventional Thirring coupling only in the strict large-$N_{\mathrm{f}}$ limit. In addition to the Thirring universality class, which is characterized by one relevant direction (also at finite $N_{\mathrm{f}}$), two further interacting fixed points occur which may define new universality classes of second-order phase transitions also involving parity-broken phases. The $N_{\mathrm{f}}$ dependence of the Thirring fixed point sheds further light on the existence of an $N_{\mathrm{f}}$-controlled quantum phase transition above which chiral symmetry remains unbroken for arbitrary large coupling, even though a definite answer will require a direct computation of competing orders.

We compute the quasinormal mode frequencies and Regge poles of the canonical acoustic hole (a black hole analogue), using three methods. First, we show how damped oscillations arise by evolving generic perturbations in the time domain using a simple finite-difference scheme. We use our results to estimate the fundamental quasinormal frequencies of the low multipolar modes $l=1,2,\dots$. Next, we apply an asymptotic method to obtain an expansion for the frequency in inverse powers of $l+1/2$ for low overtones. We test the expansion by comparing against our time-domain results, and (existing) WKB results. The expansion method is then extended to locate the Regge poles. Finally, to check the expansion of Regge poles we compute the spectrum numerically by direct integration in the frequency domain. We give a geometric interpretation of our results and comment on experimental verification.

Using a recently presented numerical code for calculating the Lorenz-gauge gravitational self-force (GSF), we compute the $O(m)$ conservative correction to the precession rate of the small-eccentricity orbits of a particle of mass $m$ moving around a Schwarzschild black hole of mass $\mathsf{M}\gg m$. Specifically, we study the gauge-invariant function $\rho (x)$, where $\rho$ is defined as the $O(m)$ part of the dimensionless ratio $({\widehat{\Omega }}_r/{\widehat{\Omega }}_{\phi }{)}^2$ between the squares of the radial and azimuthal frequencies of the orbit, and where $x=[G{c}^{-3}(\mathsf{M}+m){\widehat{\Omega }}_{\phi }{]}^{2/3}$ is a gauge-invariant measure of the dimensionless gravitational potential (mass over radius) associated with the mean circular orbit. Our GSF computation of the function $\rho (x)$ in the interval $0<x\le 1/6$ determines, for the first time, the strong-field behavior of a combination of two of the basic functions entering the effective one-body (EOB) description of the conservative dynamics of binary systems. We show that our results agree well in the weak-field regime (small $x$) with the 3rd post-Newtonian (PN) expansion of the EOB results, and that this agreement is improved when taking into account the analytic values of some of the logarithmic-running terms occurring at higher PN orders. Furthermore, we demonstrate that GSF data give access to higher-order PN terms of $\rho (x)$ and can be used to set useful new constraints on the values of yet-undetermined EOB parameters. Most significantly, we observe that an excellent global representation of $\rho (x)$ can be obtained using a simple “2-point” Padé approximant which combines 3PN knowledge at $x=0$ with GSF information at a single strong-field point (say, $x=1/6$).

We compute the transition amplitude between coherent quantum states of geometry peaked on homogeneous-isotropic metrics. We work in the context of pure gravity without matter, we use the holomorphic representations of loop quantum gravity and the Kaminski-Kisielowski-Lewandowski generalization of the new vertex, and work at first order in the vertex expansion, second order in the graph (multipole) expansion, and first order in ${\mathrm{\text{volume}}}^{-1}$. We show that the resulting amplitude is in the kernel of a differential operator whose classical limit is the canonical Hamiltonian of a Friedmann-Robertson-Walker cosmology. This result is an indication that the dynamics of loop quantum gravity defined by the new vertex reproduces the gravity part of the Friedmann equation in the appropriate limit.

We study motion of a charged particle in the vicinity of a weakly magnetized Schwarzschild black hole and focus on its bounded trajectories lying in the black hole equatorial plane. If the Lorentz force, acting on the particle, is directed outward from the black hole, there exist two qualitatively different types of trajectories; one is a curly motion and another one is a trajectory without curls. We calculated the critical value of the magnetic field for the transition between these two types. If the magnetic field is greater than the critical one, for fixed values of the particle energy and angular momentum, the bounded trajectory has curls. The curls appear as a result of the gravitational drift. The greater the value of the magnetic field, the larger is the number of curls. We constructed an approximate analytical solution for a bounded trajectory and found the gravitational drift velocity of its guiding center.

We consider possible violations of the equivalence principle through the exchange of a light “dilaton-like” scalar field. Using recent work on the quark-mass dependence of nuclear binding, we find that the dilaton-quark-mass coupling induces significant equivalence-principle-violating effects varying like the inverse cubic root of the atomic number—$A^{-1/3}$. We provide a general parametrization of the scalar couplings, but argue that two parameters are likely to dominate the equivalence-principle phenomenology. We indicate the implications of this framework for comparing the sensitivities of current and planned experimental tests of the equivalence principle.

We prove that static black holes in $n$-dimensional asymptotically flat spacetime cannot support nontrivial electric $p$-form field strengths when $(n+1)/2\le p\le n-1$. This implies, in particular, that static black holes cannot possess dipole hair under these fields.

We study the Sunyaev-Zel’dovich effect potentially generated by relativistic electrons injected from dark matter annihilation or decay in the Galaxy, and check whether it could be observed by Planck or the Atacama Large Millimeter Array (ALMA), or even imprint the current CMB data as, e.g., the specific fluctuation excess claimed from an recent reanalysis of the WMAP-5 data. We focus on high-latitude regions to avoid contamination of the Galactic astrophysical electron foreground, and consider the annihilation or decay coming from the smooth dark matter halo as well as from subhalos, further extending our analysis to a generic modeling of spikes arising around intermediate-mass black holes. We show that all these dark Galactic components are unlikely to produce any observable Sunyaev-Zel’dovich effect. For a self-annihilating dark matter particle of 10 GeV with canonical properties, the largest optical depth we find is ${\tau }_e\lesssim {10}^{-7}$ for massive isolated subhalos hosting intermediate-mass black holes. We conclude that dark matter annihilation or decay on the Galactic scale cannot lead to significant Sunyaev-Zel’dovich distortions of the CMB spectrum.

A wide range of models describing modifications to general relativity have been proposed, but no fundamental parameter set exists to describe them. Similarly, no fundamental theory exists for dark energy to parametrize its potential deviation from a cosmological constant. This motivates a model-independent search for deviations from the concordance $\mathrm{GR}+\Lambda \mathrm{CDM}$ cosmological model in large galaxy redshift surveys. We describe two model-independent tests of the growth of cosmological structure, in the form of quantities that must equal one if $\mathrm{GR}+\Lambda \mathrm{CDM}$ is correct. The first, $ϵ$, was introduced previously as a scale-independent consistency check between the expansion history and structure growth. The second, $\upsilon$, is introduced here as a test of scale-dependence in the linear evolution of matter density perturbations. We show that the ongoing and near-future galaxy redshift surveys WiggleZ, BOSS, and HETDEX will constrain these quantities at the 5–10% level, representing a stringent test of concordance cosmology at different redshifts. When redshift space distortions are used to probe the growth of cosmological structure, galaxies at higher redshift with lower bias are found to be most powerful in detecting the presence of deviations from the $\mathrm{GR}+\Lambda \mathrm{CDM}$ model. However, because many dark energy or modified gravity models predict consistency with $\mathrm{GR}+\Lambda \mathrm{CDM}$ at high redshift, it is desirable to apply this approach to surveys covering a wide range of redshifts and spatial scales.

We study those dimension 6 effective operators which generate flavor-changing quark-gluon transitions of the third generation quarks, with $t\to g+u(c)$ and $b\to g+d(s)$, and which could be of interest for LHC experiments. We analyze the contribution of these operators to $B_{s(d)}\mathrm{\text{−}}{\overline{B}}_{s(d)}$ mixing and derive limits on the corresponding effective couplings from the existing experimental data. The standard model gauge invariance relates these couplings to the couplings controlling $t\to g+u(c)$. On this basis we derive upper limits for the branching ratios of these processes. We further show that forthcoming LHC experiments might be able to probe the studied operators and the physics beyond the standard model related to them.

We present 9 new tunes of the $p_{\perp }$-ordered shower and underlying-event model in Pythia 6.4. These “Perugia” tunes update and supersede the older “S0” family. The data sets used to constrain the models include hadronic $Z^0$ decays at LEP, Tevatron min-bias data at 630, 1800, and 1960 GeV, Tevatron Drell-Yan data at 1800 and 1960 GeV, and SPS min-bias data at 200, 546, and 900 GeV. In addition to the central parameter set, called “Perugia 0,” we introduce a set of 8 related “Perugia variations” that attempt to systematically explore soft, hard, parton density, and color structure variations in the theoretical parameters. Based on these variations, a best-guess prediction of the charged track multiplicity in inelastic, nondiffractive minimum-bias events at the LHC is made. Note that these tunes can only be used with Pythia 6, not with Pythia 8.

Most searches for ultra-high-energy astrophysical neutrinos look for radio emission from the electromagnetic and hadronic showers produced in their interactions. The radio frequency spectrum and angular distribution depend on the shower development, and so are sensitive to the interaction cross sections. At energies above about ${10}^{16}\mathrm{eV}$ (in ice), the Landau-Pomeranchuk-Migdal effect significantly reduces the cross sections for the two dominant electromagnetic interactions: bremsstrahlung and pair production. At higher energies, above about ${10}^{20}\mathrm{eV}$, the photonuclear cross section becomes larger than that for pair production, and direct pair production and electronuclear interactions become dominant over bremsstrahlung. The electron interaction length reaches a maximum around ${10}^{21}\mathrm{eV}$, and then decreases slowly as the electron energy increases further. In this regime, the growth in the photon cross section and electron energy loss moderates the rise in ${\nu }_e$ shower length, which rises from $\sim 10\mathrm{m}$ at ${10}^{16}\mathrm{eV}$ to $\sim 50\mathrm{m}$ at ${10}^{19}\mathrm{eV}$ and $\sim 100\mathrm{m}$ at ${10}^{20}\mathrm{eV}$, but only to $\sim 1\mathrm{km}$ at ${10}^{24}\mathrm{eV}$. In contrast, without photonuclear and electronuclear interactions, the shower length would be over 10 km at ${10}^{24}\mathrm{eV}$.