The gravitational wave signals from coalescing Supermassive Black Hole Binaries are prime targets for the Laser Interferometer Space Antenna (LISA). With optimal data processing techniques, the LISA observatory should be able to detect black hole mergers anywhere in the Universe. The challenge is to find ways to dig the signals out of a combination of instrument noise and the large foreground from stellar mass binaries in our own galaxy. The standard procedure of matched filtering against a grid of templates can be computationally prohibitive, especially when the black holes are spinning or the mass ratio is large. Here we develop an alternative approach based on Metropolis-Hastings sampling and simulated annealing that is orders of magnitude cheaper than a grid search. For the first time, we show that it is possible to detect and characterize the signals from binary systems of Schwarzschild Black Holes that are embedded in instrument noise and a foreground containing millions of galactic binaries. Our technique is computationally efficient, robust, and applicable to both high and low signal-to-noise ratio systems.

We discuss dispersion representations for the triangle diagram $F(p_1^2,p_2^2,q^2)$, the single dispersion representation in $q^2$ and the double dispersion representation in $p_1^2$ and $p_2^2$, with special emphasis on the appearance of the anomalous singularities and the anomalous cuts in these representations. For the double dispersion representation in $p_1^2$ and $p_2^2$, the appearance of the anomalous cut in the region $q^2>0$ is demonstrated, and a new derivation of the anomalous double spectral density is given. We point out that the double spectral representation is particularly suitable for applications in the region of $p_1^2$ and/or $p_2^2$ above the two-particle thresholds. The dispersion representations for the triangle diagram in the nonrelativistic limit are studied and compared with the triangle diagram of the nonrelativistic field theory.

A near threshold enhancement in the $p\overline{p}$ invariant mass spectrum has been reported by the BELLE, BES, and BABAR collaborations for several $B$ and $J/\psi$ decays. This enhancement has been interpreted as a narrow baryonium state $X(1835)$. We investigate its nature using a $p\overline{p}$ interaction derived from a constituent quark model. This interaction does not show any $p\overline{p}$ bound state but a ${}^{3}P_0$ resonance. We show that $p\overline{p}$ final state interaction can reproduce the mass dependence of the $p\overline{p}$ mass spectrum close to the threshold observed in different $B$ and $J/\psi$ decays.

The Fourier transform of the deeply virtual Compton scattering amplitude (DVCS) with respect to the skewness parameter $\zeta =Q^2/2p·q$ can be used to provide an image of the target hadron in the boost-invariant variable $\sigma$, the coordinate conjugate to light-front time $\tau =t+z/c$. As an illustration, we construct a consistent covariant model of the DVCS amplitude and its associated generalized parton distributions using the quantum fluctuations of a fermion state at one loop in QED, thus providing a representation of the light-front wave functions (LFWFs) of a lepton in $\sigma$ space. A consistent model for hadronic amplitudes can then be obtained by differentiating the light-front wave functions with respect to the bound-state mass. The resulting DVCS helicity amplitudes are evaluated as a function of $\sigma$ and the impact parameter ${\overrightarrow{b}}_{\perp }$, thus providing a light-front image of the target hadron in a frame-independent three-dimensional light-front coordinate space. Models for the LFWFs of hadrons in $(3+1)$ dimensions displaying confinement at large distances and conformal symmetry at short distances have been obtained using the AdS/CFT method. We also compute the LFWFs in this model in invariant three-dimensional coordinate space. We find that, in the models studied, the Fourier transform of the DVCS amplitudes exhibit diffraction patterns. The results are analogous to the diffractive scattering of a wave in optics where the distribution in $\sigma$ measures the physical size of the scattering center in a one-dimensional system.

We study the radiative $\varphi \to K^0{\overline{K}}^0\gamma$ decay within a phenomenological framework by considering the contributions of the $f_0(980)$ and $a_0(980)$ scalar resonances. We calculate the branching ratio $B(\varphi \to K^0{\overline{K}}^0\gamma )$ by employing the coupling constants $g_{f_0{K}^{+}{K}^{-}}$ and $g_{a_0{K}^{+}{K}^{-}}$ as determined by different experimental groups.

In earlier papers we established quark confinement analytically in anisotropic ($2+1$)-dimensional Yang-Mills theory with two gauge coupling constants. Here we point out a few features of the confining phase. These are: 1) the string tension in the $x^2$-direction as a function of representation obeys a sine law, and 2) static adjoint sources are not confined.

The running of Newton’s constant can be taken into account by considering covariant, nonlocal generalizations of the field equations of general relativity. These generalizations involve nonanalytic functions of the d’Alembertian, as $(-\square {)}^{-\alpha }$, with $\alpha$ a noninteger number, and $\ln [-\square ]$. In this paper we define these nonlocal operators in terms of the usual two point function of a massive field. We analyze some of their properties, and present specific calculations in flat and Robertson Walker spacetimes.

A static wormhole solution for gravity in vacuum is found for odd dimensions greater than four. In five dimensions the gravitational theory considered is described by the Einstein-Gauss-Bonnet action where the coupling of the quadratic term is fixed in terms of the cosmological constant. In higher dimensions $d=2n+1$, the theory corresponds to a particular case of the Lovelock action containing higher powers of the curvature, so that in general, it can be written as a Chern-Simons form for the AdS group. The wormhole connects two asymptotically locally AdS spacetimes each with a geometry at the boundary locally given by $\mathbb{R}\times S^1\times H_{d-3}$. Gravity pulls towards a fixed hypersurface located at some arbitrary proper distance parallel to the neck. The causal structure shows that both asymptotic regions are connected by light signals in a finite time. The Euclidean continuation of the wormhole is smooth independently of the Euclidean time period, and it can be seen as instanton with vanishing Euclidean action. The mass can also be obtained from a surface integral and it is shown to vanish.

We investigate the dynamic stability of inspiraling neutron stars by performing multiple-orbit numerical relativity simulations of the binary neutron star inspiral process. By introducing eccentricities in the orbits of the neutron stars, significant changes in orbital separation are obtained within orbital timescales. We find that as the binary system evolves from apastron to periastron (as the binary separation decreases), the central rest mass density of each star decreases, thus stabilizing the stars against individual prompt collapse. As the binary system evolves from periastron to apastron, the central rest mass density increases; the neutron stars recompress as the binary separation increases.

We update and extend our previous work reconstructing the potential of a quintessence field from current observational data. We extend the cosmological data set to include new supernova data, plus information from the cosmic microwave background and from baryon acoustic oscillations. We extend the modeling by considering Padé approximant expansions as well as Taylor series, and by using observations to assess the viability of the tracker hypothesis. We find that parameter constraints have improved by a factor of 2, with a strengthening of the preference of the cosmological constant over evolving quintessence models. Present data show some signs, though inconclusive, of favoring tracker models over nontracker models under our assumptions.

The issue of the equivalence between Jordan and Einstein conformal frames in scalar-tensor gravity is revisited, with the emphasis on implementing running units in the latter. The lack of affine parametrization for timelike worldlines and the cosmological constant problem in the Einstein frame are clarified, and a paradox in the literature about cosmological singularities appearing only in one frame is solved. While, classically, the two conformal frames are physically equivalent, they seem to be inequivalent at the quantum level.

Pulsars are the most accurate naturally occurring clocks, and data about them can be used to set bounds on neutron-sector Lorentz violations. If $SO(3)$ rotation symmetry is completely broken for neutrons, then pulsars’ rotation speeds will vary periodically. Pulsar timing data limits the relevant Lorentz-violating coefficients to be smaller than $1.7\times {10}^{-8}$ at at least 90% confidence.

Strong correlations between leptogenesis and low energy $CP$ violating leptonic processes have been shown by us to exist in the minimal left-right symmetric model with spontaneous $CP$ violation. In this note, we investigate the implications of this model for the electric dipole moment of the electron. With an additional broken $U(1{)}_S$ symmetry, the seesaw scale can be lowered to close to the electroweak scale. This additional symmetry also makes the connection between $CP$ violation in quark sector to that in the lepton sector possible.

Recently Ciuchini, Pierini, and Silvestrini proposed a method for constraining CKM parameters in $B\to K\pi \pi$ and $B_s\to K\pi \pi$ through phase measurements of amplitudes involving $I=3/2$ $K^{*}\pi$ final states. We show that complementary information on CKM parameters may be obtained by studying the phases of $\Delta I=1$ $B\to (K^{*}\pi {)}_{I=1/2}$, $B_s\to (K^{*}\overline{K}{)}_{I=1}$ and $B_s\to ({\overline{K}}^{*}K{)}_{I=1}$ amplitudes. Hadronic uncertainties in these constraints from electroweak penguin operators $O_9$ and $O_{10}$, studied using flavor SU(3), are shown to be very small in $B\to K\pi \pi$ and $B_s\to K\pi \pi$ and somewhat larger in $B_s\to K\overline{K}\pi$. The first processes imply a precise linear relation between $\overline{\rho }$ and $\overline{\eta }$, with a measurable slope and an intercept at $\overline{\eta }=0$ involving a theoretical error of 0.03. The decays $B_s\to K\pi \pi$ permit a measurement of $\gamma$ involving a theoretical error below a degree. We note that while time-dependence is required when studying $B^0$ decays at the ${\rm Y}(4S)$, it may not be needed when studying $B_s$ decays at hadronic colliders.

The small-$x$ deep inelastic scattering in the saturation region is governed by the nonlinear evolution of Wilson-lines operators. In the leading logarithmic approximation it is given by the Balitsky-Kovchegov (BK) equation for the evolution of color dipoles. In the next-to-leading order (NLO) the nonlinear equation gets contributions from quark and gluon loops. In this paper I calculate the quark-loop contribution to small-$x$ evolution of Wilson lines in the NLO. It turns out that there are no new operators at the one-loop level—just as at the tree level, the high-energy scattering can be described in terms of Wilson lines. In addition, from the analysis of quark loops I find that the argument of coupling constant in the BK equation is determined by the size of the parent dipole rather than by the size of produced dipoles. These results are to be supported by future calculation of gluon loops.

We construct the general action for $N=4$, $d=1$ nonlinear supermultiplet including the most general interaction terms which depend on the arbitrary function $h$ obeying the Laplace equation on $S^3$. We find the bosonic field $B$ which depends on the components of nonlinear supermultiplet and transforms as a full time derivative under $N=4$ supersymmetry. The most general interaction is generated just by a Fayet-Iliopoulos term built from this auxiliary component. Being transformed through a full time derivative under $N=4$, $d=1$ supersymmetry, this auxiliary component $B$ may be dualized into a fourth scalar field giving rise to a four-dimensional $N=4$, $d=1$ sigma-model. We analyzed the geometry in the bosonic sector and find that it is not a hyper-Kähler one. With a particular choice of the target space metric $g$ the geometry in the bosonic sector coincides with the one which appears in heterotic (4, 0) sigma-model in $d=2$.

A new Lagrangian description that interpolates between the Nambu-Goto and Polyakov version of interacting strings is given. Certain essential modifications in the Poisson bracket structure of this interpolating theory generates noncommutativity among the string coordinates for both free and interacting strings. The noncommutativity is shown to be a direct consequence of the nontrivial boundary conditions. A thorough analysis of the gauge symmetry is presented taking into account the new modified constraint algebra, which follows from the noncommutative structures and finally a smooth correspondence between gauge symmetry and reparametrization is established.

It can be shown using operator techniques that the non-Hermitian $PT$-symmetric quantum mechanical Hamiltonian with a “wrong-sign” quartic potential $-g{x}^4$ is equivalent to a Hermitian Hamiltonian with a positive quartic potential together with a linear term. A naïve derivation of the same result in the path-integral approach misses this linear term. In a recent paper by Bender et al. it was pointed out that this term was in the nature of a parity anomaly and a more careful, discretized treatment of the path integral appeared to reproduce it successfully. However, on re-examination of this derivation we find that a yet more careful treatment is necessary, keeping terms that were ignored in that paper. An alternative, much simpler derivation is given using the additional potential that has been shown to appear whenever a change of variables to curvilinear coordinates is made in a functional integral.

We emphasize the inelasticity distribution of events detected at the IceCube neutrino telescope as an important tool for revealing new physics. This is possible because the unique energy resolution at this facility allows to separately assign the energy fractions for emergent muons and taus in neutrino interactions. As a particular example, we explore the possibility of probing second and third generation leptoquark parameter space (coupling and mass). We show that production of leptoquarks with masses $\gtrsim 250\mathrm{GeV}$ and diagonal generation couplings of $\mathcal{O}(1)$ can be directly tested if the cosmic neutrino flux is at the Waxman-Bahcall level.

A self-consistent system of interacting nonlinear spinor and scalar fields within the scope of a Bianchi type-I cosmological model filled with perfect fluid is considered. Exact self-consistent solutions to the corresponding field equations are obtained. A role of the spinor field in the evolution of the Universe is studied. It is shown that the spinor field gives rise to an accelerated mode of expansion of the Universe. Early in the evolution, the spinor field nonlinearity generates an accelerated mode of expansion. The rapid growth of the Universe in this case results in the earlier isotropization. At the later evolution the acceleration of the Universe is provided with a spinor mass.