The galactic propagation of cosmic ray strangelets is described and the resulting flux is calculated for a wide range of parameters as a prerequisite for strangelet searches in lunar soil and with an Earth orbiting magnetic spectrometer, AMS-02. While the inherent uncertainties are large, flux predictions at a measurable level are obtained for reasonable choices of parameters if strange quark matter is absolutely stable. This allows a direct test of the strange matter hypothesis.

We consider a prescription for introducing deformed dispersion relations in the bosonic string action. We find that in a subset of such theories it remains true that the embedding coordinates propagate linearly on the world sheet. While both the string modes and the center of mass propagate with deformed dispersion relations, the speed of light remains energy independent. We consider the canonical quantization of these strings and find that it is possible to choose theories so that ghost modes still decouple, as usual. We also find that there are examples where the tachyon is eliminated from the spectrum of the free bosonic string.

For a certain example of a “doubly special relativity theory” the modified space-time Lorentz transformations are obtained from the momentum space transformations by using canonical methods. In the sequel an energy-momentum dependent space-time metric is constructed, which is essentially invariant under the modified Lorentz transformations. By associating such a metric to every Planck cell in space and to the energy-momentum contained in it, a solution of the problem of macroscopic bodies in doubly special relativity is suggested.

We extend the study of Bogomol'nyi-Prasad-Sommerfield (BPS) equations in $\mathcal{N}=1/2$ super Yang-Mills theory to the case of models with gauge symmetry breaking. We first consider an Abelian gauge-Higgs supersymmetric Lagrangian in $d=4$ dimensional Euclidean space obtained by deforming $\mathcal{N}=1$ superspace. The supermultiplets include chiral and vector superfields and its bosonic content coincides with that of the Abelian-Higgs model where vortex solutions to the BPS equation are known to exist in the undeformed case. We also consider the $d=3$ dimensional reduction of a non-Abelian $d=4$ deformed model and study its deformed BPS equations, showing the existence of new monopole solutions which depend on the deformation parameter.

Addressing the question of whether the Hawking effect depends on degrees of freedom at ultrahigh (e.g., Planckian) energies/momenta, we propose three rather general conditions on these degrees of freedom under which the Hawking effect is reproduced to lowest order. As a generalization of Corley’s results, we present a rather general model based on nonlinear dispersion relations satisfying these conditions together with a derivation of the Hawking effect for that model. However, we also demonstrate counter-examples, which do not appear to be unphysical or artificial, displaying strong deviations from Hawking’s result. Therefore, whether real black holes emit Hawking radiation remains an open question and could give nontrivial information about Planckian physics.

We investigate the (conservative) dynamics of binary black holes using the Hamiltonian formulation of the post-Newtonian (PN) equations of motion. The Hamiltonian we use includes spin-orbit coupling, spin-spin coupling, and mass monopole/spin-induced quadrupole interaction terms. We investigate the qualitative effects of these terms on the orbits; in the case of both quasicircular and eccentric orbits, we search for the presence of chaos (using the method of Lyapunov exponents) for a large variety of initial conditions. For quasicircular orbits, we find no chaotic behavior for black holes with total mass $10–40M_{\odot }$ when initially at a separation corresponding to a Newtonian gravitational-wave (GW) frequency less than $\sim 150\mathrm{H}\mathrm{z}$. Only for rather small initial radial distances (corresponding to a GW frequency larger than $\sim 150\mathrm{H}\mathrm{z}$), for which spin-spin induced oscillations in the radial separation are rather important, do we find chaotic solutions, and even then they are rare. Moreover, these chaotic quasicircular orbits are of questionable astrophysical significance, since they originate from direct parametrization of the equations of motion rather than from widely separated binaries evolving to small separations under gravitational radiation reaction. In the case of highly eccentric orbits, which for ground-based interferometers are not astrophysically favored, we again find chaotic solutions, but only at pericenters so small that higher order PN corrections, especially higher spin PN corrections, should also be taken into account. Taken together, our surveys of quasicircular and eccentric orbits find chaos only for orbits that are either of dubious astrophysical interest for ground-based interferometers or which violate the approximations required for the equations of motion to be physically valid at the post-Newtonian order considered.

The cosmic acceleration was discovered in one of the brane-based models. We are interested in discriminating this model from the dark energy by tomographic cosmic shear. Growth factors are different in the two models when one adjusts parameters to get nearly identical $H(z)$. The two models could be distinguished with independent determinations of both geometrical factors and the growth factor. We introduce new parametrizations to separate the influence of geometry and the influence of growth on cosmic shear maps. We find that future observations will be able to distinguish between both models.

We discuss the sensitivity to anisotropies of stochastic gravitational-wave backgrounds (GWBs) observed via space-based interferometer. In addition to the unresolved galactic binaries as the most promising GWB source of the planned Laser Interferometer Space Antenna (LISA), the extragalactic sources for GWBs might be detected in the future space missions. The anisotropies of the GWBs thus play a crucial role to discriminate various components of the GWBs. We study general features of antenna pattern sensitivity to the anisotropies of GWBs beyond the low-frequency approximation. We show that the sensitivity of space-based interferometer to GWBs is severely restricted by the data combinations and the symmetries of the detector configuration. The spherical harmonic analysis of the antenna pattern functions reveals that the angular power of the detector response increases with frequency and the detectable multipole moments with effective sensitivity $h_{\mathrm{e}\mathrm{f}\mathrm{f}}\sim {10}^{-20}{\mathrm{H}\mathrm{z}}^{-1/2}$ may reach $\ell \sim 8–10$ at $f\sim f_{*}=10\mathrm{m}\mathrm{H}\mathrm{z}$ in the case of the single LISA detector. However, the cross correlation of optimal interferometric variables is blind to the monopole ($\ell =0$) intensity anisotropy, and also to the dipole ($\ell =1$) in some case, irrespective of the frequency band. Besides, all the self-correlated signals are shown to be blind to the odd multipole moments ($\ell =\mathrm{o}\mathrm{d}\mathrm{d}$), independently of the frequency band.

We study black hole solutions in $R^4\times S^1$ space, using an expansion to second order in the square of the ratio of the radius of the horizon, $\mu$, and the circumference of the compact dimension, $L$. A study of geometric and thermodynamic properties indicates that the black hole fills the space in the compact dimension at $ϵ=(\mu /L{)}^2\simeq 0.1$. At the same value of $ϵ$ the entropies of the uniform black string and of the black hole are approximately equal.

Linear perturbation theory is appropriate to describe small oscillations of stars, while a mild nonlinearity is still tractable perturbatively but requires one to consider mode coupling, i.e., to take into account second order effects. It is natural to start to look at this problem by considering the coupling between linear radial and nonradial modes. A radial pulsation may be thought of as an important component of an overall mildly nonlinear oscillation, e.g., of a protoneutron star. Radial pulsations of spherical compact objects do not per se emit gravitational waves but, if the coupling between the existing first order radial and nonradial modes is efficient in driving and possibly amplifying the nonradial oscillations, one may expect the appearance of nonlinear harmonics, and gravitational radiation could then be produced to a significant level. More in general, mode coupling typically leads to an interesting phenomenology, thus it is worth investigating in the context of star perturbations. In this paper we develop the relativistic formalism to study the coupling of radial and nonradial first order perturbations of a compact spherical star. From a mathematical point of view, it is convenient to treat the two sets of perturbations as separately parametrized, using a 2-parameter perturbative expansion of the metric, the energy-momentum tensor and Einstein equations in which $\lambda$ is associated with the radial modes, $ϵ$ with the nonradial perturbations, and the $\lambda ϵ$ terms describe the coupling. This approach provides a well-defined framework to consider the gauge dependence of perturbations, allowing us to use $ϵ$ order gauge-invariant nonradial variables on the static background and to define new second order $\lambda ϵ$ gauge-invariant variables representing the result of the nonlinear coupling. We present the evolution and constraint equations for our variables outlining the setup for numerical computations, and briefly discuss the surface boundary conditions in terms of the second order $\lambda ϵ$ Lagrangian pressure perturbation.

We study the renormalized energy-momentum tensor of gravitons in a de Sitter space-time. After canonically quantizing only the physical degrees of freedom, we adopt the standard adiabatic subtraction used for massless minimally coupled scalar fields as a regularization procedure and find that the energy density of gravitons in the $E(3)$ invariant vacuum is proportional to $H^4$, where $H$ is the Hubble parameter, but with a positive sign. According to this result the scalar expansion rate, which is gauge invariant in de Sitter space-time, is increased by the fluctuations. This implies that gravitons may then add to conformally coupled matter in driving the Starobinsky model of inflation.

We use stellar structure dynamics arguments to extract bounds on the relevant parameters of two scalar field models: the putative scalar field mediator of a fifth force with a Yukawa potential and the new variable mass particle models. We also analyze the impact of a constant solar inbound acceleration, such as the one reported by the Pioneer anomaly, on stellar astrophysics. We consider the polytropic gas model to estimate the effect of these models on the hydrostatic equilibrium equation and fundamental quantities such as the central temperature. The current bound on the solar luminosity is used to constrain the relevant parameters of each model.

Weak lensing is a potentially robust and model-independent cosmological probe, but its accuracy is dependent on knowledge of the redshift distribution of the source galaxies used. The most robust way to determine the redshift distribution is via spectroscopy of a subsample of the source galaxies. We forecast constraints from combining cosmic microwave background (CMB) anisotropies with cosmic shear using a spectroscopically determined redshift distribution, varying the number of spectra $N_{\mathrm{s}\mathrm{p}\mathrm{e}\mathrm{c}}$ obtained from 64 to $\infty$. The source redshift distribution is expanded in a Fourier series, and the amplitudes of each mode are considered as parameters to be constrained via both the spectroscopic and weak lensing data. We assume independent source redshifts, and consider in what circumstances this is a good approximation (the sources are clustered and for narrow spectroscopic surveys with many objects this results in the redshifts being correlated). It is found that for the surveys considered and for a prior of 0.04 on the calibration parameters, the addition of redshift information makes significant improvements on the constraints on the cosmological parameters; however, beyond $N_{\mathrm{s}\mathrm{p}\mathrm{e}\mathrm{c}}\sim \mathrm{f}\mathrm{e}\mathrm{w}\times {10}^3$ the addition of further spectra will make only a very small improvement to the cosmological parameters. We find that a better calibration makes large $N_{\mathrm{s}\mathrm{p}\mathrm{e}\mathrm{c}}$ more useful. Using an eigenvector analysis, we find that the improvement continues with even higher $N_{\mathrm{s}\mathrm{p}\mathrm{e}\mathrm{c}}$, but not in directions that dominate the uncertainties on the standard cosmological parameters.

We consider baryon-baryon bound states in $\mathrm{S}\mathrm{U}(3)$ lattice QCD with two flavors, $2\times 2$ spin matrices in $2+1$ dimensions, and in an imaginary time formulation. For small hopping parameter $0<\kappa \ll 1$ and large glueball mass, we show the existence of an isospin $3/2$ baryon, with asymptotic mass $-3\ln \kappa$ and isolated dispersion curve. Baryon-baryon bound states of isospin zero and one are found with approximate binding energy ${\kappa }^2/8$ and ${\kappa }^2/24$, respectively, using a ladder approximation to a Bethe-Salpeter equation. The baryon-baryon interaction associated with the ladder approximation is an energy independent spatial range-one attractive potential with an $\mathcal{O}({\kappa }^2)$ strength. The attractive potential does not have a meson exchange interpretation. Six-point gauge field correlations give rise to attraction and counterbalance the Pauli repulsion to give a vanishing zero-range potential. The overall range-one potential results from a complicated interaction between the isospin components of the constituent quarks of the baryons.

The mean free path of neutrino-free electron gas interaction has been calculated by taking into account the neutrino electromagnetic form factors and the possibility of neutrino oscillation. It is shown that the form factor effect becomes significant for a neutrino magnetic moment ${\mu }_{\nu }\ge {10}^{-10}{\mu }_B$ and for a neutrino radius $R\ge {10}^{-6}{\mathrm{M}\mathrm{e}\mathrm{V}}^{-1}$. The mean free path is found to be sensitive to the ${\nu }_e-{\nu }_{\mu }$ and ${\nu }_e-{\nu }_e^R$ transition probabilities.

We analyze the phase diagram of a 3-flavor Nambu–Jona-Lasinio model at finite temperature $T$ and chemical potentials ${\mu }_u,{\mu }_d,{\mu }_s$. We study the competition of pion and kaon condensation and we propose a physical situation in which kaon condensation could be led only by light quark finite densities.

The implementation of various methods for the determination of $\gamma$ through direct $CP$ violation arising in the interference of $b\to c$ and $b\to u$ processes in charged as well as neutral $B$ meson decays are considered. We show that the inclusion of $D^0$ resulting from $D^{*0}\to D^0+{\pi }^0(\gamma )$, say, via $B\to K{D}^{*0}$ makes a significant difference in the attainable accuracy for $\gamma$. Both exclusive and inclusive decays of the $B^{\pm }$ and $B^0$ to states containing $D^0/{\overline{D}}^0$ followed by both inclusive and exclusive decays of the $D^0$ are discussed. It is shown that with statistics which might be obtained at $B$ factories ($5–10\times {10}^8$ $B$ pairs) a $1\sigma$ determination of $\gamma$ to $\approx \pm 8°$ may be possible, depending on the efficiency of reconstruction, backgrounds, and the details of the decay amplitudes involved. The role of data from a charm factory as well as effects of $D^0$ mixing are discussed. Extraction of $\gamma$ with accuracy that is roughly commensurate with the intrinsic theory error of these methods (i.e., around 0.1%), which is an important goal, will require $>{10}^{10}$ $B$ pairs, namely, a super $B$ factory.

Using the CLEO-III detector at CESR we study $e^{+}{e}^{-}$ collisions in the center-of-mass energy close to, or above, ${\Lambda }_b^0{\overline{\Lambda }}_b^0$ production threshold. We search for evidence of ${\Lambda }_b^0{\overline{\Lambda }}_b^0$ resonance production and set upper limits based on inclusive hadron production as a barometer of ${\Lambda }_b^0{\overline{\Lambda }}_b^0$ production.