A scaling analysis is made of the order parameter describing monopole condensation at the deconfining transition of $N_f=2$ QCD around the chiral point. In accordance with scaling properties of the specific heat, studied in a previous paper, scaling is consistent with a first order transition. The status of dual superconductivity of the vacuum as a mechanism of color confinement is reviewed.

Dimensional regularization is applied to the computation of the gravitational wave field generated by compact binaries at the third post-Newtonian (3PN) approximation. We generalize the wave generation formalism from isolated post-Newtonian matter systems to $d$ spatial dimensions, and apply it to point masses (without spins), modeled by delta-function singularities. We find that the quadrupole moment of point-particle binaries in harmonic coordinates contains a pole when $\epsilon \equiv d-3\to 0$ at the 3PN order. It is proved that the pole can be renormalized away by means of the same shifts of the particle world lines as in our recent derivation of the 3PN equations of motion. The resulting renormalized (finite when $\epsilon \to 0$) quadrupole moment leads to unique values for the ambiguity parameters $\xi$, $\kappa$, and $\zeta$, which were introduced in previous computations using Hadamard’s regularization. Several checks of these values are presented. These results complete the derivation of the gravitational waves emitted by inspiralling compact binaries up to the 3.5PN level of accuracy which is needed for detection and analysis of the signals in the gravitational wave antennas LIGO/VIRGO and LISA.

Gravitational wave bursters are sources which emit repeatedly bursts of gravitational waves, and have been recently suggested as potentially interesting candidates for gravitational wave (GW) detectors. Mechanisms that could give rise to a GW burster can be found for instance in highly magnetized neutron stars (the “magnetars” which explain the phenomenon of soft gamma repeaters), in accreting neutron stars and in hybrid stars with a quark core. We point out that these sources have very distinctive experimental signatures. In particular, as already observed in the $\gamma$-ray bursts from soft gamma repeaters, the energy spectrum of the events is a power-law, $dN\sim E^{-\gamma }dE$ with $\gamma \simeq 1.6$, and they have a distribution of waiting times (the times between one outburst and the next) significantly different from the distribution of uncorrelated events. We discuss possible detection strategies that could be used to search for these events in existing gravitational wave detectors.

Based upon the lattice Dirac operator satisfying the Ginsparg-Wilson relation, we investigate canonical formulation of massless fermion on the spatial lattice. For free fermion system exact chiral symmetry can be implemented without species doubling. In the presence of gauge couplings the chiral symmetry is violated. We show that the divergence of the axial vector current is related to the chiral anomaly in the classical continuum limit.

We present a complete analysis of the neutral fermion sector of supersymmetric $E_6$-inspired low-energy models containing an extra $SU(2)$, concentrating on the alternative left-right and inert models. We show that the $R$-parity conserving scenario always exhibits a large Dirac mass for ${\nu }_L$ with maximal mixing with an isosinglet neutrino, and that $R$-parity violating scenarios do not change the picture other than allowing further mixing with another isosinglet. In order to recover standard model phenomenology, additional assumptions in the form of discrete symmetries and/or new interactions are needed. We introduce and investigate the discrete symmetry method and higher-dimensional operators as mechanisms for solving the neutrino mass and mixing problems in these models.

The neutral fermion sectors of $E_6$-inspired low-energy models, in particular, the alternative left-right and inert models, are considered in detail within the nonsupersymmetric scenario. We show that in their simplest form, these models always predict, for each generation, the lightest neutrino to be a $SU(2{)}_L$ singlet, as well as two extra neutrinos with masses of the order of the up-quark mass. In order to recover standard model phenomenology, additional assumptions in the form of discrete symmetries and/or new interactions are needed. These are classified as the discrete symmetry, higher-dimensional operators, and additional neutral fermion methods. The discrete symmetry method can solve the problem, but requires additional Higgs doublets that do not get vacuum expectation values. The higher-dimensional operators method predicts no sterile neutrino, and that the active neutrinos mix with a heavy isodoublet neutrino, thus slightly suppressing the couplings of active neutrinos, with interesting phenomenological implications. The additional neutral fermion method also predicts this suppression, and also naturally includes one or more sterile neutrinos. This scenario allows the existence of sterile neutrino(s) in either a $\mathbf{3}+\mathbf{1}$ or $\mathbf{2}+\mathbf{2}$ structure at low energies, which are favored by the Los Alamos Liquid Scintillation Neutrino Detector result.

We report on a search for the pair production of scalar leptoquarks (LQ), using $191{\mathrm{pb}}^{-1}$ of proton-antiproton collision data recorded by the CDF experiment during Run II of the Tevatron. The leptoquarks are sought via their decay into a neutrino and quark yielding missing transverse energy and several jets of large transverse energy. No evidence for LQ production is observed, and limits are set on $\sigma (p\overline{p}\to \mathrm{LQ}\overline{\mathrm{LQ}}X\to \nu \overline{\nu }q\overline{q}X)$. Using a next-to-leading order theoretical prediction of the cross section for LQ production, we exclude first-generation LQ in the mass interval 78 to $117\mathrm{GeV}/c^2$ at the 95% confidence level for $BR(\mathrm{LQ}\to \nu q)=100\%$.

We study the spacetime structures of the static solutions in the $n$-dimensional Einstein-Gauss-Bonnet-$\Lambda$ system systematically. We assume the Gauss-Bonnet coefficient $\alpha$ is non-negative and a cosmological constant is either positive, zero, or negative. The solutions have the $(n-2)$-dimensional Euclidean submanifold, which is the Einstein manifold with the curvature $k=1$, 0, and $-1$. We also assume $4\tilde{\alpha }/{\ell }^2\le 1$, where $\ell$ is the curvature radius, in order for the sourceless solution ($M=0$) to be defined. The general solutions are classified into plus and minus branches. The structures of the center, horizons, infinity, and the singular point depend on the parameters $\alpha$, ${\ell }^2$, $k$, $M$, and branches complicatedly so that a variety of global structures for the solutions are found. In our analysis, the $\tilde{M}\mathrm{\text{−}}r$ diagram is used, which makes our consideration clear and enables easy understanding by visual effects. In the plus branch, all the solutions have the same asymptotic structure at infinity as that in general relativity with a negative cosmological constant. For the negative-mass parameter, a new type of singularity called the branch singularity appears at nonzero finite radius $r=r_b>0$. The divergent behavior around the singularity in Gauss-Bonnet gravity is milder than that around the central singularity in general relativity. There are three types of horizons: inner, black hole, and cosmological. In the $k=1,0$ cases, the plus-branch solutions do not have any horizon. In the $k=-1$ case, the radius of the horizon is restricted as $r_h<\sqrt{2\tilde{\alpha }}$ ($r_h>\sqrt{2\tilde{\alpha }}$) in the plus (minus) branch. The black hole solution with zero or negative mass exists in the plus branch even for the zero or positive cosmological constant. There is also the extreme black hole solution with positive mass. We briefly discuss the effect of the Gauss-Bonnet corrections on black hole formation in a collider and the possibility of the violation of the third law of the black hole thermodynamics.

We analyze a class of exact type II solutions of the Robinson-Trautman family which contain pure radiation and (possibly) a cosmological constant. It is shown that these spacetimes exist for any sufficiently smooth initial data, and that they approach the spherically symmetric Vaidya-(anti-)de Sitter metric. We also investigate extensions of the metric, and we demonstrate that their order of smoothness is in general only finite. Some applications of the results are outlined.

It is usually assumed that relic neutrinos possess a Fermi-Dirac distribution, acquired during thermal equilibrium in the Early Universe. However, various mechanisms could introduce strong distortions in this distribution. We perform a Bayesian likelihood analysis including the first moments of the three active neutrino distributions as free parameters, and show that current cosmological observations of light element abundances, Cosmic Microwave Background anisotropies and Large Scale Structures are compatible with very large deviations from the standard picture. We also calculate the bounds on nonthermal distortions which can be expected from future observations, and stress that Cosmic Microwave Background and Large Scale Structures data alone will not be sensitive enough in order to distinguish between nonthermal distortions in the neutrino sector and extra relativistic degrees of freedom. This degeneracy could be removed by additional constraints from primordial nucleosynthesis or independent neutrino mass scale measurements.

We propose an extension of the original thought experiment proposed by Geroch, which sparked much of the actual debate and interest on black hole thermodynamics, and show that the generalized second law of thermodynamics is in compliance with it.

We elucidate the one-loop twistor-space structure corresponding to momentum-space maximally helicity-violating diagrams. We also discuss the infrared divergences, and argue that only a limited set of maximally helicity-violating diagrams contain them. We show how to introduce a twistor-space regulator corresponding to dimensional regularization for the infrared-divergent diagrams. We also evaluate explicitly the “holomorphic anomaly” pointed out by Cachazo, Svrček, and Witten, and use the result to define modified differential operators which can be used to probe the twistor-space structure of one-loop amplitudes.

We study the phenomenon of Unruh effect in a massless scalar field theory quantized on the light front in the general light-front frame. We determine the uniformly accelerating coordinates in such a frame and through a direct transformation show that the propagator of the theory has a thermal character in the uniformly accelerating coordinate system with a temperature given by Tolman’s law. We also carry out a systematic analysis of this phenomenon from the Hilbert space point of view and show that the vacuum of this theory appears as a thermal vacuum to a Rindler observer with the same temperature as given by Tolman’s law.

Recently a new recursion relation for tree-level gluon amplitudes in gauge theory has been discovered. We solve this recursion to obtain explicit formulas for the closed set of amplitudes with arbitrarily many positive and negative helicity gluons in a split helicity configuration. The solution admits a simple diagrammatic expansion in terms of “zigzag” diagrams. We comment on generalizations of this result.

We investigate the rotational core collapse of a rapidly rotating relativistic star by means of a $3+1$ hydrodynamical simulation in conformally flat spacetime of general relativity. We concentrate our investigation to the bounce of the rotational core collapse, since potentially most of the gravitational waves from it are radiated around the core bounce. The dynamics of the star is started from a differentially rotating equilibrium star of $T/W\sim 0.16$ ($T$ is the rotational kinetic energy and $W$ is the gravitational binding energy of the equilibrium star), depleting the pressure to initiate the collapse and to exceed the threshold of dynamical bar instability. Our finding is that the collapsing star potentially forms a bar when the star has a toroidal structure due to the redistribution of the angular momentum at the core bounce. On the other hand, the collapsing star weakly forms a bar when the star has a spheroidal structure. We also find that the bar structure of the star is destroyed when the torus is destroyed in the rotational core collapse. Since the collapse of a toroidal star potentially forms a bar, it can be a promising source of gravitational waves which will be detected in advanced LIGO.

It is shown that flat spacetime can be dressed with a real scalar field that satisfies the nonlinear Klein-Gordon equation without curving spacetime. Surprisingly, this possibility arises from the nonminimal coupling of the scalar field with the curvature, since a footprint of the coupling remains in the energy-momentum tensor even when gravity is switched off. Requiring the existence of solutions with vanishing energy-momentum tensor fixes the self-interaction potential as a local function of the scalar field depending on two coupling constants. The solutions describe shock waves and, in the Euclidean continuation, instanton configurations in any dimension. As a consequence of this effect, the tachyonic solutions of the free massive Klein-Gordon equation become part of the vacuum.

It is argued that small values of the neutrino masses may be due to anthropic selection effects. If this is the case, then the combined mass of the three neutrino species is expected to be $\sim 1\mathrm{eV}$, neutrinos causing a non-negligible suppression of galaxy formation.

We consider the effects of a gas of closed strings (treated quantum mechanically) on a background where one dimension is compactified on a circle. After we address the effects of a time-dependent background on aspects of the string spectrum that concern us, we derive the energy-momentum tensor for a string gas and investigate the resulting space-time dynamics. We show that a variety of trajectories are possible for the radius of the compactified dimension, depending on the nature of the string gas, including a demonstration within the context of general relativity (i.e. without a dilaton) of a solution where the radius of the extra dimension oscillates about the self-dual radius, without invoking matter that violates the various energy conditions. In particular, we find that in the case where the string gas is in thermal equilibrium, the radius of the compactified dimension dynamically stabilizes at the self-dual radius, after which a period of usual Friedmann-Robertson-Walker cosmology of the three uncompactified dimensions can set in. We show that our radion stabilization mechanism requires a stringy realization of inflation as scalar field driven inflation invalidates our mechanism. We also show that our stabilization mechanism is consistent with observational bounds.

This paper presents first results of an ongoing study of a possible association between muon enhancements at ground observed by the TUPI telescope and transient events such as the Sun’s X-ray activity. The analysis of the observed phenomenon by using the GOES satellite archive data seems to indicate that on most cases the Ground Level Enhancements (GLEs) could potentially be associated with solar flares. We show that small-scale solar flares, those with prompt X-ray emission classified as C class (power above ${10}^{-6}\mathrm{Watts}{m}^{-2}$ at 1 AU) may give rise to GLEs, probably associated with solar protons and ions arriving to the Earth as a coherent particle pulse. The TUPI telescope’s high performance with these energetic solar particles arises mainly from: (i) its high counting rate (up to $\sim 100$ KHz). This value in most cases is around 100 times higher than other detectors at ground and (ii) due to its tracking system. The telescope is always looking near the direction of the IMF lines. The GLE’s delay in relation of the X-ray prompt emission suggest that shock driven by corona mass ejection (CME) is an essential requirement for the particle acceleration efficiency.

Weak lensing of the CMB changes the unlensed temperature anisotropy and polarization power spectra. Accounting for the lensing effect will be crucial to obtain accurate parameter constraints from sensitive CMB observations. Methods for computing the lensed power spectra using a low-order perturbative expansion are not good enough for percent-level accuracy. Nonperturbative flat-sky methods are more accurate, but curvature effects change the spectra at the 0.3%–1% level. We describe a new, accurate, and fast, full-sky correlation-function method for computing the lensing effect on CMB power spectra to better than 0.1% at $l\lesssim 2500$ (within the approximation that the lensing potential is linear and Gaussian). We also discuss the effect of nonlinear evolution of the gravitational potential on the lensed power spectra. Our fast numerical code is publicly available.