We analyze the response of a detector with a uniform acceleration $\alpha$ in $\kappa$-Minkowski spacetime using the first order perturbation theory. The monopole detector is coupled to a massless complex scalar field in such a way that it is sensitive to the noncommutativity of spacetime present in the $\kappa$-deformation. The response function deviates from the thermal distribution of Unruh temperature at the order of $1/\kappa$ and vanishes exponentially as the proper time of the detector exceeds a certain critical time, a logarithmic function of $\kappa$. This suggests that the Unruh temperature becomes not only fuzzy but also eventually decreases to zero in this model.

We present accurate simulations of the dynamical bar-mode instability in full general relativity focusing on two aspects which have not been investigated in detail in the past, namely, on the persistence of the bar deformation once the instability has reached its saturation and on the precise determination of the threshold for the onset of the instability in terms of the parameter $\beta =T/|W|$. We find that generic nonlinear mode-coupling effects appear during the development of the instability and these can severely limit the persistence of the bar deformation and eventually suppress the instability. In addition, we observe the dynamics of the instability to be strongly influenced by the value $\beta$ and on its separation from the critical value ${\beta }_c$ marking the onset of the instability. We discuss the impact these results have on the detection of gravitational waves from this process and provide evidence that the classical perturbative analysis of the bar-mode instability for Newtonian and incompressible Maclaurin spheroids remains qualitatively valid and accurate also in full general relativity.

The new 182 gold supernova Ia data, the baryon acoustic oscillation measurement and the shift parameter determined from the Sloan Digital Sky Survey, and the three-year Wilkinson Microwave Anisotropy Probe data are combined to reconstruct the dark energy equation of state parameter $w(z)$ and the deceleration parameter $q(z)$. We find that the strongest evidence of acceleration happens around the redshift $z\sim 0.2$ and the stringent constraints on $w(z)$ lie in the redshift range $z\sim 0.2–0.5$. At the sweet spot, $-1.2<w(z)<-0.6$ for the dark energy parametrization $w(z)=w_0+w_{a}z/(1+z{)}^2$ at the $3\sigma$ confidence level. The transition redshift $z_t$ when the Universe underwent the transition from deceleration to acceleration is derived to be $z_t={0.36}_{-0.08}^{+0.23}$. The combined data is also applied to find out the geometry of the Universe, and we find that at the $3\sigma$ confidence level, $|{\Omega }_k|\lesssim 0.05$ for the simple one-parameter dark energy model, and $-0.064<{\Omega }_k<0.028$ for the $\Lambda \mathrm{CDM}$ model.

Integrated Sachs-Wolfe (ISW) measurements, which involve cross-correlating the microwave background anisotropies with the foreground large-scale structure (e.g. traced by galaxies/quasars), have proven to be an interesting probe of dark energy. We show that magnification bias, which is the inevitable modulation of the foreground number counts by gravitational lensing, alters both the scale dependence and amplitude of the observed ISW signal. This is true especially at high redshifts because (1) the intrinsic galaxy-temperature signal diminishes greatly back in the matter-dominated era, (2) the lensing efficiency increases with redshift and (3) the number count slope generally steepens with redshift in a magnitude limited sample. At $z\gtrsim 2$, the magnification-temperature correlation dominates over the intrinsic galaxy-temperature correlation and causes the observed ISW signal to increase with redshift, despite dark energy subdominance—a result of the fact that magnification probes structures all the way from the observer to the sources. Ignoring magnification bias therefore can lead to (significantly) erroneous conclusions about dark energy. While the lensing modulation opens up an interesting high $z$ window for ISW measurements, high redshift measurements are not expected to add much new information to low redshift ones if dark energy is indeed the cosmological constant. This is because lensing introduces significant covariance across redshifts. The most compelling reasons for pursuing high redshift ISW measurements are to look for potential surprises such as early dark energy domination or signatures of modified gravity. We conclude with a discussion of existing measurements, the highest redshift of which is at the margin of being sensitive to the magnification effect. We also develop a formalism which might be of more general interest: to predict biases in estimating parameters when certain physical effects are ignored in interpreting observations.

We consider the nonlinear dynamics of inflaton fragmentation during and after preheating in the simplest model of chaotic inflation. While the earlier regime of parametric resonant particle production and the later turbulent regime of interacting fields evolving towards equilibrium are well identified and understood, the short intermediate stage of violent nonlinear dynamics remains less explored. Lattice simulations of fully nonlinear preheating dynamics show specific features of this intermediate stage: occupation numbers of the scalar particles are peaked, scalar fields become significantly nongaussian and the field dynamics become chaotic and irreversible. Visualization of the field dynamics in position space reveals that nonlinear interactions generate nongaussian inflaton inhomogeneities with very fast growing amplitudes. The peaks of the inflaton inhomogeneities coincide with the peaks of the scalar field(s) produced by parametric resonance. When the inflaton peaks reach their maxima, they stop growing and begin to expand. The subsequent dynamics is determined by expansion and superposition of the scalar waves originating from the peaks. Multiple wave superposition results in phase mixing and turbulent wave dynamics. Thus, the short intermediate stage is defined by the formation, expansion and collision of bubblelike field inhomogeneities associated with the peaks of the original gaussian field. This process is qualitatively similar to the bubblelike inflaton fragmentation that occurs during tachyonic preheating after hybrid or new inflation.

Recently, many efforts have been made to build dark energy models whose equation-of-state parameter can cross the so-called phantom divide $w_{\mathrm{de}}=-1$. One of them is the so-called hessence dark energy model in which the role of dark energy is played by a noncanonical complex scalar field. In this work, we develop a simple method based on Hubble parameter $H(z)$ to reconstruct the hessence dark energy. As examples, we use two familiar parametrizations for $H(z)$ and fit them to the latest 182 type Ia supernovae Gold dataset. In the reconstruction, measurement errors are fully considered.

Low frequency gravitational wave detectors, such as the Laser Interferometer Space Antenna (LISA), will have to contend with large foregrounds produced by millions of compact galactic binaries in our galaxy. While these galactic signals are interesting in their own right, the unresolved component can obscure other sources. The science yield for the LISA mission can be improved if the brighter and more isolated foreground sources can be identified and regressed from the data. Since the signals overlap with one another, we are faced with a “cocktail party” problem of picking out individual conversations in a crowded room. Here we present and implement an end-to-end solution to the galactic foreground problem that is able to resolve tens of thousands of sources from across the LISA band. Our algorithm employs a variant of the Markov chain Monte Carlo (MCMC) method, which we call the blocked annealed Metropolis-Hastings (BAM) algorithm. Following a description of the algorithm and its implementation, we give several examples ranging from searches for a single source to searches for hundreds of overlapping sources. Our examples include data sets from the first round of mock LISA data challenges.

We use perturbation theory and the relativistic Cowling approximation to numerically compute characteristic oscillation modes of rapidly rotating relativistic stars which consist of a perfect fluid obeying a polytropic equation of state. We present a code that allows the computation of modes of arbitrary order. We focus here on the overall distribution of frequencies. As expected, we find an infinite pressure mode spectrum extending to infinite frequency. In addition we obtain an infinite number of inertial mode solutions confined to a finite, well-defined frequency range which depends on the compactness and the rotation frequency of the star. For nonaxisymmetric modes we observe how this range is shifted with respect to the axisymmetric ones, moving towards negative frequencies and thus making all $m>2$ modes unstable. We discuss whether our results indicate that the star’s spectrum must have a continuous part, as opposed to simply containing an infinite number of discrete modes.

We discuss a possibility that the neutron electric dipole moment (NEDM) can be calculated in lattice QCD simulations in the presence of the $CP$-violating $\theta$ term. In this paper we measure the energy difference between spin-up and spin-down states of the neutron in the presence of a uniform and static external electric field. We first test this method in quenched QCD with the renormalization group improved gauge action on a ${16}^3\times 32$ lattice at $a^{-1}\simeq 2\mathrm{GeV}$, employing two different lattice fermion formulations, the domain-wall fermion and the clover fermion for quarks, at relatively heavy quark mass $(m_{PS}/m_V\simeq 0.85)$. We obtain nonzero values of the NEDM from calculations with both fermion formulations. We next consider some systematic uncertainties of our method for the NEDM, using ${24}^3\times 32$ lattice at the same lattice spacing only with the clover fermion. We finally investigate the quark mass dependence of the NEDM and observe a nonvanishing behavior of the NEDM toward the chiral limit. We interpret this behavior as a manifestation of the pathology in the quenched approximation.

We study the finite temperature transition in QCD with three flavors of equal masses using the R and RHMC algorithms on lattices with temporal extent $N_{\tau }=4$ and 6. For the transition temperature in the continuum limit we find $r_0{T}_c=0.429(8)$ for the light pseudoscalar mass corresponding to the endpoint of the 1st order transition region. When comparing the results obtained with the R and RHMC algorithms for p4fat3 action we see no significant step-size errors down to a lightest pseudoscalar mass of $m_{\mathrm{ps}}{r}_0=0.4$.

The various decay modes of the type $B\to \gamma D^{*}$ are dynamically different. In general, there are factorized contributions of pole and nonpole type, and pseudoscalar exchange contributions at meson level. The purpose of this paper is to point out that the decay modes $\overline{B_{d,s}^0}\to \gamma D^{*0}$ have small contributions from such mechanisms, in contrast to the decay modes $\overline{B_{d,s}^0}\to \gamma \overline{D^{*0}}$ and $B^{-}\to \gamma D_{s,d}^{*-}$. On the other hand, there are nonfactorizable $1/N_c$ suppressed contributions from colored four quark operators obtained from Fierz transformations of the standard four quark operators. Such $1/N_c$ suppressed terms involving emission of soft gluons are calculated within a heavy-light chiral quark model, and they are found to dominate the amplitudes for the decay modes $\overline{B_{d,s}^0}\to \gamma D^{*0}$. We estimate the branching ratio for these modes in the low velocity regime, i.e. in the heavy quark limit, both for the $b$ and the $c$ quarks. In this limit we obtain a value $\simeq 1\times {10}^{-5}$ for $\overline{B_d^0}\to \gamma D^{*0}$, and $\simeq 6\times {10}^{-7}$ for $\overline{B_s^0}\to \gamma D^{*0}$. We expect substantial corrections to these numbers because the energy gap between the $b$- and $c$-quark masses are significantly bigger than 1 GeV. However, we expect that our estimates of the amplitudes for $\overline{B_{d,s}^0}\to \gamma D^{*0}$ give the right order of magnitude because other mechanisms are numerically suppressed in this special case.

We explore the potential of the CERN Large Hadron Collider (LHC) to test the dynamical torsion parameters. The form of the torsion action can be established from the requirements of consistency of effective quantum field theory. The most phenomenologically relevant part of the torsion tensor is dual to a massive axial vector field. This axial vector has geometric nature, that means it does not belong to any representation of the gauge group of the SM extension or GUT theory. At the same time, torsion should interact with all fermions, that opens the way for the phenomenological applications. We demonstrate that LHC collider can establish unique constraints on the interactions between fermions and torsion field considerably exceeding present experimental lower bounds on the torsion couplings and its mass. It is also shown how possible nonuniversal nature of torsion couplings due to the renormalization group running between the Planck and TeV energy scales can be tested via the combined analysis of Drell-Yan and $t\overline{t}$ production processes.

In this article we study the diffractive photoproduction of heavy quarks in hadronic ($pp/pA/AA$) interactions for Tevatron and LHC energies. The integrated cross section and rapidity distribution for the process $h_1{h}_2\to h_1{h}_{2}Q\overline{Q}$ ($h_i=p$, $A$ and $Q=c$, $b$) are estimated using the color glass condensate (CGC) formalism. Our results indicate that this production channel has larger cross sections than the competing reactions of double diffractive production and coherent $AA$ reactions initiated by two-photon collisions.

We examine the link approach to constructing a lattice theory of $\mathcal{N}=2$ super Yang-Mills theory in two dimensions. The goal of this construction is to provide a discretization of the continuum theory which preserves all supersymmetries at nonzero lattice spacing. We show that this approach suffers from an inconsistency and argue that a maximum of just one of the supersymmetries can be implemented on the lattice.

We study a five dimensional $SU(3)$ nonsupersymmetric gauge theory compactified on $M^4\times S^1/Z_2$ and discuss the gauge hierarchy in the scenario of the gauge-Higgs unification. Making use of the calculability of the Higgs potential and a curious feature that coefficients in the potential are given by discrete values, we find two models, in which the large gauge hierarchy is realized, that is, the weak scale is naturally obtained from a unique large scale such as a grand unified theory scale or the Planck scale. The size of the Higgs mass is also discussed in each model. One of the models we find realizes both large gauge hierarchy and consistent Higgs mass, and shows that the Higgs mass becomes heavier as the compactified scale becomes smaller.

We construct a superpotential for the general $\mathcal{N}=\frac{1}{2}$ supersymmetric gauge theory coupled to chiral matter in the fundamental and adjoint representations, and investigate the one-loop renormalizability of the theories.

Reformulating the instantons in a complex plane for tunneling or transmitting states, we calculate the pair-production rate of charged fermions in a spatially localized electric field, illustrated by the Sauter electric field $E_0{\mathrm{sech}}^2(z/L)$, and in a temporally localized electric field such as $E_0{\mathrm{sech}}^2(t/T)$. The integration of the quadratic part of WKB instanton actions over the frequency and transverse momentum leads to the pair-production rate obtained by the worldline-instanton method, including the prefactor, of Phys. Rev. D 72, 105004 (2005) and 73, 065028 (2006). It is further shown that the WKB instanton action plus the next-to-leading-order contribution in spinor QED equals the WKB instanton action in scalar QED, thus justifying why the WKB instanton in scalar QED can work for the pair production of fermions. Finally we obtain the pair-production rate in a spatially localized electric field together with a constant magnetic field in the same direction.

We give a solution of the wave equation for massless, or massive spin-2 particles propagating in a gravitational background. The solution is covariant, gauge-invariant and exact to first order in the background gravitational field. The background contribution is confined to a phase factor from which geometrical and physical optics can be derived. The phase also describes Mashhoon’s spin-rotation coupling and, in general, the spin-gravity interaction.

It is shown that, in the Bondi-Sachs gauge that fixes the speed of incoming light rays to the value 1, the Einstein equations coupled to a scalar field in spherical symmetry are cast into a symmetric-hyperbolic system of equations for the scalar field, lapse and shift as fundamental variables. In this system of equations, the lapse and shift are incoming characteristic fields, and the scalar field has three components: incoming, outgoing and static. A constraint-preserving boundary condition is prescribed by imposing the projection of the Einstein equation normal to the boundary at the outer value of the radial coordinate. The boundary condition specifies one of the two incoming metric fields. The remaining incoming metric field and the incoming scalar field component need to be specified arbitrarily. Numerical simulations of the scattering of the scalar field by a black hole in the nonlinear regime are presented that illustrate interesting facts about black-hole physics and the behavior of the characteristic variables of the problem.

We construct two new classes of spacetimes generated by spinning and traveling magnetic sources in ($n+1$)-dimensional Einstein-Maxwell-dilaton gravity with Liouville-type potential. These solutions are neither asymptotically flat nor (A)dS. The first class of solutions which yields a ($n+1$)-dimensional spacetime with a longitudinal magnetic field and $k$ rotation parameters have no curvature singularity and no horizons, but have a conic geometry. We show that when one or more of the rotation parameters are nonzero, the spinning branes have a net electric charge that is proportional to the magnitude of the rotation parameters. The second class of solutions yields a static spacetime with an angular magnetic field and has no curvature singularity, no horizons, and no conical singularity. Although one may add linear momentum to the second class of solutions by a boost transformation, one does not obtain a new solution. We find that the net electric charge of these traveling branes with one or more nonzero boost parameters is proportional to the magnitude of the velocity of the branes. We also use the counterterm method and calculate the conserved quantities of the solutions.