We construct the generalized monodromy matrix $\widehat{\mathcal{M}}(\omega )$ of two-dimensional string effective action by introducing the T-duality group properties. The integrability conditions with general solutions depending on spectral parameter are given. This construction is investigated for the exactly solvable Wess, Zumino, Novikov, and Witten model in pp-wave limit when $B=0$.

We present a formulation for computing equilibria composed of a rotating black hole and a massive self-gravitating torus in general relativity. Such a system is a plausible outcome formed after stellar core collapse of massive and supermassive stars as well as after a merger of a black hole-neutron star binary. In our formulation, the black hole is modeled in the puncture framework. The numerical solutions for equilibria are computed for rapidly rotating black holes and for a wide range of mass ratio of the black hole and torus. The equilibria obtained in this paper can be used for studying nonaxisymmetric instabilities, runaway instability, and magnetorotational instability of a self-gravitating accretion torus around a rotating black hole in numerical relativity. We also remark that the relation among the area, mass, and spin of rotating black holes are slightly modified by the torus.

We study the inspiral, merger, and ringdown of unequal mass black hole binaries by analyzing a catalogue of numerical simulations for seven different values of the mass ratio (from $q=M_2/M_1=1$ to $q=4$). We compare numerical and post-Newtonian results by projecting the waveforms onto spin-weighted spherical harmonics, characterized by angular indices $(l,m)$. We find that the post-Newtonian equations predict remarkably well the relation between the wave amplitude and the orbital frequency for each $(l,m)$, and that the convergence of the post-Newtonian series to the numerical results is nonmonotonic. To leading order, the total energy emitted in the merger phase scales like ${\eta }^2$ and the spin of the final black hole scales like $\eta$, where $\eta =q/(1+q{)}^2$ is the symmetric mass ratio. We study the multipolar distribution of the radiation, finding that odd-$l$ multipoles are suppressed in the equal mass limit. Higher multipoles carry a larger fraction of the total energy as $q$ increases. We introduce and compare three different definitions for the ringdown starting time. Applying linear-estimation methods (the so-called Prony methods) to the ringdown phase, we find resolution-dependent time variations in the fitted parameters of the final black hole. By cross correlating information from different multipoles, we show that ringdown fits can be used to obtain precise estimates of the mass and spin of the final black hole, which are in remarkable agreement with energy and angular momentum balance calculations.

A detailed study of the geometries that emerge by a gravitating generalized Yang monopole in even dimensions is carried out, in particular, those which present black hole and cosmological horizons. This two-horizon system is thermally unstable. The process of thermalization will drive both horizons to coalesce. This limit is what is profusely studied in this paper. It is shown that even though coordinate distance shrinks to zero, physical distance does not. So, there is some remaining space whose geometry has been computed and identified as a generalized Nariai solution. The thermal properties of this new spacetime are then calculated. Topics such as the elliptical relation between radii of spheres in the geometry or a discussion about whether a mass-type term should be present in the line element or not are also included.

We investigate a cosmological model with a big-brake singularity in the future: while the first time derivative of the scale factor goes to zero, its second time derivative tends to minus infinity. Although we also discuss the classical version of the model in some detail, our main interest lies in its quantization. We formulate the Wheeler-DeWitt equation and derive solutions describing wave packets. We show that all such solutions vanish in the region of the classical singularity, a behavior which we interpret as singularity avoidance. We then discuss the same situation in loop quantum cosmology. While this leads to a different factor ordering, the singularity is avoided there, too.

We consider the future dynamics of a transient phantom dominated phase of the universe in loop quantum cosmology (LQC) and in the Randall-Sundrum braneworld, which both have a nonstandard Friedmann equation. We find that for a certain class of potentials, the Hubble parameter oscillates with simple harmonic motion in the LQC case and therefore avoids any future singularity. For more general potentials we find that damping effects eventually lead to the Hubble parameter becoming constant. On the other hand in the braneworld case we find that although the type I singularity can be avoided, the scale factor still diverges at late times.

We analyze the effect of variation of fundamental couplings and mass scales on primordial nucleosynthesis in a systematic way. The first step establishes the response of primordial element abundances to the variation of a large number of nuclear physics parameters, including nuclear binding energies. We find a strong influence of the $n-p$ mass difference (for the ${}^4\mathrm{He}$ abundance), of the nucleon mass (for deuterium), and of $A=3$, 4, 7 binding energies (for ${}^3\mathrm{He}$, ${}^6\mathrm{Li}$, and ${}^7\mathrm{Li}$). A second step relates the nuclear parameters to the parameters of the standard model of particle physics. The deuterium, and, above all, ${}^7\mathrm{Li}$ abundances depend strongly on the average light quark mass $\widehat{m}\equiv (m_u+m_d)/2$. We calculate the behavior of abundances when variations of fundamental parameters obey relations arising from grand unification. We also discuss the possibility of a substantial shift in the lithium abundance while the deuterium and ${}^4\mathrm{He}$ abundances are only weakly affected.

We consider the effects on the primordial power spectrum of a period of radiation-dominated expansion prior to the inflationary era. If inflation lasts a total of only 60 e-folds or so, the boundary condition for quantum modes cannot be taken in the short-wavelength limit as in the standard perturbation calculation. Instead, the boundary condition is set by the vacuum state of the prior radiation-dominated epoch, which only corresponds to the inflationary vacuum state in the ultraviolet limit. This altered vacuum state results in a modulation of the inflationary power spectrum. We calculate the modification to a best-fit model from the WMAP3 data set, and find that power is suppressed at large scales. The modified power spectrum is favored only very weakly by the WMAP3 temperature and polarization data.

We explore the requirements for a Lyman-$\alpha$ forest survey designed to measure the angular diameter distance and Hubble parameter at $2\lesssim z\lesssim 4$ using the standard ruler provided by baryonic acoustic oscillations (BAO). The goal would be to obtain a high enough density of sources to probe the three-dimensional density field on the scale of the BAO feature. A percent-level measurement in this redshift range can almost double the Dark Energy Task Force figure of merit, relative to the case with only a similar precision measurement at $z\sim 1$, if the Universe is not assumed to be flat. This improvement is greater than the one obtained by doubling the size of the $z\sim 1$ survey, with Planck and a weak Sloan Digital Sky Survey-like $z=0.3$ BAO measurement assumed in each case. Galaxy BAO surveys at $z\sim 1$ may be able to make an effective $\mathrm{Ly}\alpha$ forest measurement simultaneously at minimal added cost, because the required number density of quasars is relatively small. We discuss the constraining power as a function of area, magnitude limit (density of quasars), resolution, and signal-to-noise of the spectra. For example, a survey covering 2000 sq. deg. and achieving $S/N=1.8$ per Å at $g=23$ ($\sim 40\mathrm{quasars}$ per sq. deg.) with an $R\gtrsim 250$ spectrograph is sufficient to measure both the radial and transverse oscillation scales to 1.4% from the $\mathrm{Ly}\alpha$ forest (or better, if fainter magnitudes and possibly Lyman-break galaxies can be used). At fixed integration time and in the sky-noise-dominated limit, a wider, noisier survey is generally more efficient; the only fundamental upper limit on noise being the need to identify a quasar and find a redshift. Because the $\mathrm{Ly}\alpha$ forest is much closer to linear and generally better understood than galaxies, systematic errors are even less likely to be a problem.

We have searched for gravitational waves (GWs) associated with the SGR $1806-20$ hyperflare of 27 December 2004. This event, originating from a Galactic neutron star, displayed exceptional energetics. Recent investigations of the x-ray light curve’s pulsating tail revealed the presence of quasiperiodic oscillations (QPOs) in the 30–2000 Hz frequency range, most of which coincides with the bandwidth of the LIGO detectors. These QPOs, with well-characterized frequencies, can plausibly be attributed to seismic modes of the neutron star which could emit GWs. Our search targeted potential quasimonochromatic GWs lasting for tens of seconds and emitted at the QPO frequencies. We have observed no candidate signals above a predetermined threshold, and our lowest upper limit was set by the 92.5 Hz QPO observed in the interval from 150 s to 260 s after the start of the flare. This bound corresponds to a (90% confidence) root-sum-squared amplitude ${\mathrm{h}}_{\mathrm{rss}\mathrm{\text{−}}\det }^{90\%}=4.5\times {10}^{-22}\mathrm{\text{strain}}{\mathrm{Hz}}^{-1/2}$ on the GW waveform strength in the detectable polarization state reaching our Hanford (WA) 4 km detector. We illustrate the astrophysical significance of the result via an estimated characteristic energy in GW emission that we would expect to be able to detect. The above result corresponds to $7.7\times {10}^{46}\mathrm{erg}$ ($=4.3\times {10}^{-8}{\mathrm{M}}_{\odot }{\mathrm{c}}^2$), which is of the same order as the total (isotropic) energy emitted in the electromagnetic spectrum. This result provides a means to probe the energy reservoir of the source with the best upper limit on the GW waveform strength published and represents the first broadband asteroseismology measurement using a GW detector.

Binary black holes can form efficiently in dense young stellar clusters, such as the progenitors of globular clusters, via a combination of gravitational segregation and cluster evaporation. We use simple analytic arguments supported by detailed $N$-body simulations to determine how frequently black holes born in a single stellar cluster should form binaries, be ejected from the cluster, and merge through the emission of gravitational radiation. We then convolve this “transfer function” relating cluster formation to black-hole mergers with (i) the distribution of observed cluster masses and (ii) the star formation history of the Universe, assuming that a significant fraction $g_{\mathrm{cl}}$ of star formation occurs in clusters and that a significant fraction $g_{\mathrm{evap}}$ of clusters undergo this segregation and evaporation process. We predict future ground-based gravitational wave detectors could observe $\sim 500(g_{\mathrm{cl}}/0.5)(g_{\mathrm{evap}}/0.1)$ double black-hole mergers per year, and the presently operating LIGO interferometer would have a chance (50%) at detecting a merger during its first full year of science data. More realistically, advanced LIGO and similar next-generation gravitational wave observatories provide unique opportunities to constrain otherwise inaccessible properties of clusters formed in the early Universe.

We investigate the effect of unparticles in the pure annihilation type decays $B^{-}\to D_s^{-}\varphi$ and $D_s^{-}{K}^{*0}$. Since these decays have only annihilation contributions their branching ratios are expected to be very small in the standard model and the direct $CP$ asymmetry parameters to be zero. We find that due to the unparticle effect these branching ratios can be significantly enhanced from their standard model values. Furthermore, sizable nonzero direct $CP$ violation could also be possible in these channels due to the presence of intrinsic $CP$ conserving phase in the unparticle propagator.

We present results for kaon decay widths of baryon resonances from a relativistic study with constituent quark models. The calculations are done in the point form of Poincaré-invariant quantum mechanics with a spectator-model decay operator. We obtain covariant predictions of the Goldstone-boson-exchange and a variant of the one-gluon-exchange constituent quark models for all kaon decay widths of established baryon resonances. They are generally characterized by underestimating the available experimental data. In particular, the widths of kaon decays with decreasing strangeness in the baryon turn out to be extremely small. We also consider the nonrelativistic limit, leading to the familiar elementary emission model, and demonstrate the importance of relativistic effects. It is found that the nonrelativistic approach evidently misses sensible influences from Lorentz boosts and some essential spin-coupling terms.

We study the bosonic excitations in the favorite cubic three flavor crystalline Larkin-Ovchinikov-Fulde-Ferrell phases of QCD. We calculate in the Ginzburg-Landau approximation the masses of the eight pseudo Nambu-Goldstone bosons (NGB) present in the low energy theory. We also compute the decay constants of the massless NGB Goldstones associated to superfluidity as well as those of the eight pseudo NGB. Differently from the corresponding situation in the color-flavor-locking phase, we find that meson condensation phases are not expected in the present scenario.

Results from a phenomenological analysis for diffractive hadroproduction of heavy flavors at high energies are reported. Diffractive production of charm, bottom, and top are calculated using Regge factorization, taking into account recent experimental determination of the diffractive parton density functions in the Pomeron by the H1 Collaboration at DESY-HERA. In addition, multiple-Pomeron corrections are considered through the rapidity gap survival probability factor. We give numerical predictions for single diffractive as well as double Pomeron exchange cross sections, which agree with the available data for diffractive production of charm and beauty. We make estimates which could be compared to future measurements at the CERN LHC.

Neutrino oscillation experiments and direct bounds on absolute masses constrain neutrino mass differences to fall into the microwave energy range, for most of the allowed parameter space. As a consequence of these recent phenomenological advances, older constraints on radiative neutrino decays based on diffuse background radiations and assuming strongly hierarchical masses in the eV range are now outdated. We thus derive new bounds on the radiative neutrino lifetime using the high precision cosmic microwave background spectral data collected by the Far Infrared Absolute Spectrophotometer instrument on board the Cosmic Background Explorer. The lower bound on the lifetime is between a $\mathrm{\text{few}}\times {10}^{19}\mathrm{s}$ and $\sim 5\times {10}^{20}\mathrm{s}$, depending on the neutrino mass ordering and on the absolute mass scale. However, due to phase space limitations, the upper bound in terms of the effective magnetic moment mediating the decay is not better than $\sim {10}^{-8}$ Bohr magnetons. We also comment about possible improvements of these limits, by means of recent diffuse infrared photon background data. We compare these bounds with preexisting limits coming from laboratory or astrophysical arguments. We emphasize the complementarity of our results with others available in the literature.

We discuss a scenario to extract up to 150 MeV neutrinos at a standard beta-beam facility using one and two detectors off-axis. In particular we show that the high-energy component of the neutrino fluxes can be subtracted through a specific combination of the response of two off-axis detectors. A systematic analysis of the neutrino fluxes using different detector geometries is presented, as well as a comparison with the expected fluxes at a low-energy beta-beam facility. The presented option could offer an alternative way to perform low-energy neutrino experiments.

The spatial ’t Hooft loop, which is a disorder parameter dual to the temporal Wilson loop, is calculated using the nonperturbative Yang-Mills vacuum wave functional determined previously by a variational solution of the Yang-Mills Schrödinger equation in Coulomb gauge. It is shown that this wave functional yields indeed a perimeter law for large spatial ’t Hooft loops signaling confinement.

We study the properties of chaos in the motions of a spinning test particle in Schwarzschild spacetime. We characterize the chaos using the power spectrum of the time series of $z$ components of the particle’s position. It is found that the pattern of the power spectrum shows not only white noise but also $1/f$-type fluctuation, depending on the value of the total angular momentum $J$ and the spin $S$ of the test particle. Therefore we succeed in classifying the chaotic motions, which have been classified as simply chaotic ones in former works, into the two distinct types. One is $1/f$, and the other is white noise. Based on this classification, we plot, in the two-dimensional parameter space $(J,S)$, the phase diagram for the properties of the chaos. This phase diagram enables us in principle to guess the properties of the system $(J,S)$ by observing the dynamics of the test particle, even if the motion is chaotic. Furthermore, we detect that the origin of the $1/f$ fluctuation is that the particle motion stagnates around regular orbits (tori), while traveling back and forth between them, which is called “stagnant motion” or “sticky motion” in Hamiltonian dynamical systems. The point is that the difference of the property of the chaos or the power spectra is due to the topological structure of the phase space, which in turn is governed by the physical parameter set $(J,S)$ of the system. From this point of view, the chaos we found in this system is not always merely random.

Effective equations often provide powerful tools to develop a systematic understanding of detailed properties of a quantum system. This is especially helpful in quantum cosmology where several conceptual and technical difficulties associated with the full quantum equations can be avoided in this way. Here, effective equations for Wheeler-DeWitt and loop quantizations of spatially flat, isotropic cosmological models sourced by a massive or interacting scalar are derived and studied. The resulting systems are remarkably different from that given for a free, massless scalar. This has implications for the coherence of evolving states and the realization of a bounce in loop quantum cosmology.