We consider the electric dipole form factor, $F_3(q^2)$, as well as the Dirac and Pauli form factors, $F_1(q^2)$ and $F_2(q^2)$, of the nucleon in the light-front formalism. We derive an exact formula for $F_3(q^2)$ to complement those known for $F_1(q^2)$ and $F_2(q^2)$. We derive the light-front representation of the discrete symmetry transformations and show that time-reversal- and parity-odd effects are captured by phases in the light-front wave functions. We thus determine that the contributions to $F_2(q^2)$ and $F_3(q^2)$, Fock state by Fock state, are related, independent of the fundamental mechanism through which $CP$ violation is generated. Our relation is not specific to the nucleon, but, rather, is true of spin-$1/2$ systems in general, be they lepton or baryon. The empirical values of the anomalous magnetic moments, in concert with empirical bounds on the associated electric dipole moments, can better constrain theories of $CP$ violation. In particular, we find that the neutron and proton electric dipole moments echo the isospin structure of the anomalous magnetic moments, ${\kappa }^n\sim -{\kappa }^p$.

We revisit the question of the convergence of lattice perturbation theory for a pure $SU(3)$ lattice gauge theory in four dimensions. Using a series for the average plaquette up to order 10 in the weak coupling parameter ${\beta }^{-1}$, we show that the analysis of the extrapolated ratio and the extrapolated slope suggests the possibility of a nonanalytical power behavior of the form $(1/\beta -1/5.7(1){)}^{1.0(1)}$, in agreement with another analysis based on the same assumption. This would imply that the third derivative of the free energy density diverges near $\beta =5.7$. We show that the peak in the third derivative of the free energy present on $4^4$ lattices disappears if the size of the lattice is increased isotropically up to a ${10}^4$ lattice. On the other hand, on $4\times L^3$ lattices, a jump in the third derivative persists when $L$ increases, and follows closely the known values of ${\beta }_c$ for the first order finite temperature transition. We show that the apparent contradiction at zero temperature can be resolved by moving the singularity in the complex $1/\beta$ plane. If the imaginary part of the location of the singularity $\Gamma$ is within the range $0.001<\Gamma <0.01$, it is possible to limit the second derivative of $P$ within an acceptable range without affecting drastically the behavior of the perturbative coefficients. We discuss the possibility of checking the existence of these complex singularities by using the strong coupling expansion or calculating the zeroes of the partition function.

We examine the radiative corrections to an extension of the standard model containing a Lorentz-violating axial vector parameter. At second order in this parameter, the photon self-energy is known to contain terms that violate gauge invariance. Previously, this has been treated as a pathology, but it is also possible to take the gauge noninvariant terms at face value. These terms then make Lorentz-violating contributions to the photon mass, and directly measured limits on the photon mass can be used to set bounds on the Lorentz violation at better than the ${10}^{-22}\mathrm{GeV}$ level.

We study the trinified model, ${\mathrm{SU}(3)}_C\times {\mathrm{SU}(3)}_L\times {\mathrm{SU}(3)}_R\times {\mathbb{Z}}_3$, with the minimal Higgs sector required for symmetry breaking. There are five Higgs doublets, and gauge-coupling unification results if all five are at the weak scale, without supersymmetry. The radiative seesaw mechanism yields sub-eV neutrino masses, without the need for intermediate scales, additional Higgs fields, or higher-dimensional operators. The proton lifetime is above the experimental limits, with the decay modes $p\to \overline{\nu }{K}^{+}$ and $p\to {\mu }^{+}{K}^0$ potentially observable. We also consider supersymmetric versions of the model, with one or two Higgs doublets at the weak scale. The radiative seesaw mechanism fails with weak-scale supersymmetry due to the nonrenormalization of the superpotential, but operates in the split-SUSY scenario.

Considering Ginsparg-Wilson type fermions dynamically in lattice QCD simulations is a challenging task. The hope is to be able to approach smaller pion masses and to eventually reach physical situations. The price to pay is substantially higher computational costs. Here we discuss first results of a dynamical implementation of the so-called chirally improved fermions, a Dirac operator that obeys the Ginsparg-Wilson condition approximately. The simulation is for two species of mass-degenerate quarks on ${12}^3\times 24$ lattices with spatial size up to 1.55 fm. Implementation of the hybrid Monte-Carlo algorithm and an analysis of the results are presented.

We present complete analytical $\mathcal{O}({\epsilon }^2)$ results on the one-loop amplitudes relevant for the next-to-next-to-leading order (NNLO) quark-parton model description of the hadroproduction of heavy quarks as given by the so-called loop-by-loop contributions. All results of the perturbative calculation are given in the dimensional regularization scheme. These one-loop amplitudes can also be used as input in the determination of the corresponding NNLO cross sections for heavy flavor photoproduction, and in photon-photon reactions.

We investigate finite volume effects in the pattern of chiral symmetry breaking. To this end we employ a formulation of the Schwinger-Dyson equations on a torus which reproduces results from the corresponding lattice simulations of staggered quarks and from the overlap action. Studying the volume dependence of the quark propagator we find quantitative differences with the infinite volume result at small momenta and small quark masses. We estimate the minimal box length $L$ below which chiral perturbation theory cannot be applied to be $L\simeq 1.6\mathrm{fm}$. In the infinite volume limit we find a chiral condensate of $|⟨\overline{q}q⟩{|}_{\overline{MS}}^{2\mathrm{GeV}}=(253\pm 5\mathrm{MeV}{)}^3$, an up/down quark mass of $m_{\overline{MS}}^{2\mathrm{GeV}}=4.1\pm 0.3\mathrm{MeV}$ and a pion decay constant which is only 10% smaller than the experimental value.

We analyze the lepton sector of a left-right model based on the gauge group $SU(2{)}_L\times SU(2{)}_R\times U(1)$, concentrating mainly on neutrino properties. Using the seesaw mechanism and a horizontal symmetry, we keep the right-handed symmetry breaking scale relatively low, while simultaneously satisfying phenomenological constraints on the light neutrino masses. We take the right-handed scale to be of order 10’s of TeV and perform a full numerical analysis of the model’s parameter space, subject to experimental constraints on neutrino masses and mixings. The numerical procedure yields results for the right-handed neutrino masses and mixings and the various $CP$-violating phases. We also discuss phenomenological applications of the model to neutrinoless double beta decay, lepton-flavor-violating decays (including decays such as $\tau \to 3\mu$) and leptogenesis.

Recently, early superinflation driven by the phantom field has been proposed and studied. The detection of primordial gravitational waves is an important means to know the state of the very early universe. In this brief report we discuss in detail the gravitational wave background excited during the phantom superinflation, compared with that of the usual inflation model.

We present the complete set of $N=1$, $D=4$ quantum algebras associated to massive superparticles. We obtain the explicit solution of these algebras realized in terms of unconstrained operators acting on the Hilbert space of superfields. These solutions are expressed using the chiral, antichiral and tensorial projectors which define the three irreducible representations of the supersymmetry on the superfields. In each case the space-time variables are noncommuting and their commutators are proportional to the internal angular momentum of the representation. The quantum algebra associated to the chiral or the antichiral projector is the one obtained by the quantization of the Casalbuoni-Brink-Schwarz (superspin 0) massive superparticle. We present a new superparticle action for the (superspin $1/2$) case and show that their wave functions are the ones associated to the irreducible tensor multiplet.

We study the tree level scattering or emission of $n$ closed superstrings from a decaying non-BPS brane in Type II superstring theory. We attempt to calculate generic $n$-point superstring disk amplitudes in the rolling tachyon background. We show that these can be written as infinite power series of Toeplitz determinants, related to expectation values of a periodic function in Circular Unitary Ensembles. Further analytical progress is possible in the special case of bulk-boundary disk amplitudes. These are interpreted as probability amplitudes for emission of a closed string with initial conditions perturbed by the addition of an open string vertex operator. This calculation has been performed previously in bosonic string theory, here we extend the analysis for superstrings. We obtain a result for the average energy of closed superstrings produced in the perturbed background.

We discuss appropriate infrared cutoffs and their adiabatic limit for field theories on the noncommutative Minkowski space in the Yang-Feldman formalism. In order to do this, we consider a mass term as interaction term. We show that an infrared cutoff can be defined quite analogously to the commutative case and that the adiabatic limit of the two-point function exists and coincides with the expectation, to all orders.

Scalar particles—i.e., scalar-field excitations—in de Sitter space exhibit behavior unlike either classical particles in expanding space or quantum particles in flat spacetime. Their energies oscillate forever, and their interactions are spread out in energy. Here it is shown that these features characterize not only normal-mode excitations spread out over all space, but localized particles or wave packets as well. Both one-particle and coherent states of a massive, minimally coupled scalar field in de Sitter space, associated with classical wave packets, are constructed explicitly. Their energy expectation values and corresponding Unruh-DeWitt detector response functions are calculated. Numerical evaluation of these quantities for a simple set of classical wave packets clearly displays these novel features. Hence, given the observed accelerating expansion of the Universe, it is possible that observation of an ultralow-mass scalar particle could yield direct confirmation of distinct predictions of quantum field theory in curved spacetime.

Quantum gravity is investigated in the limit of a large number of space-time dimensions $d$, using as an ultraviolet regularization the simplicial lattice path integral formulation. In the weak field limit the appropriate expansion parameter is determined to be $1/d$. For the case of a simplicial lattice dual to a hypercube, the critical point is found at $k_c/\lambda =1/d$ (with $k=1/8\pi G$) separating a weak coupling from a strong coupling phase, and with $2d^2$ degenerate zero modes at $k_c$. The strong coupling, large $G$, phase is then investigated by analyzing the general structure of the strong coupling expansion in the large $d$ limit. Dominant contributions to the curvature correlation functions are described by large closed random polygonal surfaces, for which excluded volume effects can be neglected at large $d$, and whose geometry we argue can be approximated by unconstrained random surfaces in this limit. In large dimensions the gravitational correlation length is then found to behave as $|\log (k_c-k){|}^{1/2}$, implying for the universal gravitational critical exponent the value $\nu =0$ at $d=\infty$.

New axisymmetric stationary solutions of the vacuum Einstein equations in five-dimensional asymptotically flat spacetimes are obtained by using solitonic solution-generating techniques. The new solutions are shown to be equivalent to the four-dimensional multisolitonic solutions derived from particular class of four-dimensional Weyl solutions and to include different black rings from those obtained by Emparan and Reall.

In an affine prolongation of general relativity, the minimal coupling of Dirac fields to gravity naturally provides an axial current interaction. We demonstrate that the cancellation of the translational curvature, i.e. torsion, in the chiral anomaly induces a dynamical axion coupled with gravitational strength. Because of a geometrical identity, our torsion-induced pseudoscalar couples to the Einstein equations with an effective energy-momentum tensor which automatically satisfies the quintessence condition $w<-1/3$ for the equation of state parameter. In a toy model of an axion-dominated Universe, this leads to an anharmonic oscillatory evolution for which the deceleration parameter is within the range of current observations.

The spatial clustering of galaxies in galaxy clusters implies that the background of infrared (IR) light in the intracluster medium (ICM) may exceed the universal background. Cosmic rays injected within the ICM propagate diffusively and at low energies are trapped there for cosmological times. The photopion production interactions of cosmic rays with the IR photons are responsible for the generation of neutrinos whose detection may shed some light on the origin and propagation of high energy cosmic rays in the universe. Here we discuss our calculations of the flux of neutrinos from single clusters as well as the contribution of photopion production in clusters of galaxies to the diffuse neutrino background.

We predict the triple differential cross section of the Drell-Yan process $p\overline{p}\to l^{+}{l}^{-}X$ in the kinematical regimes relevant for the upcoming PANDA experiment, using a model that accounts for quark virtuality as well as primordial transverse momentum. We find a cross section magnitude of up to 10 nb in the low mass region. A measurement with $10\%$ accuracy is desirable in order to constrain the partonic transverse momentum dispersion and the spectral function width within $\pm 50$ MeV and to study their evolution with $M$ and $\sqrt{s}$.

Generalized Breit-Wigner expressions describing both single and coupled scalar resonances are derived by combining chiral symmetry and unitarization. Bare scalar propagators are dressed by two-pion loops, results are analytical, and there is little model dependence, since no form factors are used. In the single resonance case, two free coupling parameters are present, which allow flexible descriptions of masses, widths, and pole positions. The usual $K$-matrix unitarization procedure is recovered as an approximation. When two resonances are present, intermediate pion loops give rise to a coupled channel problem and there is no simple relationship between the unitarized amplitude and Breit-Wigner expressions for individual resonances. Eventually, we approximate and generalize our results and give friendly expressions that can be used in the parametrization of scalar resonances in data analyses.

In this work we study the phenomenological consequences of the environment dependence of neutrino mass on solar and reactor neutrino phenomenology. We concentrate on mass varying neutrino scenarios in which the enviroment dependence is induced by Yukawa interactions of a light neutral scalar particle which couples to neutrinos and matter. Under the assumption of one mass-scale dominance, we perform a global analysis of solar and KamLAND neutrino data which depends on 4 parameters: the two standard oscillation parameters, $\Delta m_{0,21}^2$ and ${tan}^2{\theta }_{12}$, and two new coefficients which parameterize the environment dependence of the neutrino mass. We find that, generically, the inclusion of the environment dependent terms does not lead to a very statistically significant improvement on the description of the data in the most favored MSW LMA (or LMA-I) region. It does, however, substantially improve the fit in the high-$\Delta m^2$ LMA (or LMA-II) region which can be allowed at $98.9\%$ CL. Conversely, the analysis allow us to place stringent constraints on the size of the environment dependence terms which can be translated on a bound on the product of the effective neutrino-scalar (${\lambda }^{\nu }$) and matter-scalar (${\lambda }^N$) Yukawa couplings, as a function of the scalar field mass ($m_S$) in these models, $|{\lambda }^{\nu }{\lambda }^N|(\frac{{10}^{-7}\mathrm{eV}}{m_S}{)}^2\le 3.0\times {10}^{-28}$ (at $90\%$ CL) .