Recently, a topological field theory of membrane matter coupled to BF theory in arbitrary spacetime dimensions was proposed [J. C. Baez and A. Perez, Adv. Theor. Math. Phys. 11, 3 (2007).]. In this paper, we discuss various aspects of the four-dimensional theory. First, we study classical solutions leading to an interpretation of the theory in terms of strings propagating on a flat spacetime. We also show that the general classical solutions of the theory are in one-to-one correspondence with solutions of Einstein’s equations in the presence of distributional matter (cosmic strings). Second, we quantize the theory and present, in particular, a prescription to regularize the physical inner product of the canonical theory. We show how the resulting transition amplitudes are dual to evaluations of Feynman diagrams coupled to three-dimensional quantum gravity. Finally, we remove the regulator by proving the topological invariance of the transition amplitudes.

Binary neutron stars (NSNS) are expected to be among the leading sources of gravitational waves observable by ground-based laser interferometers and may be the progenitors of short-hard gamma-ray bursts. We present a series of general relativistic NSNS coalescence simulations both for unmagnetized and magnetized stars. We adopt quasiequilibrium initial data for circular, irrotational binaries constructed in the conformal thin-sandwich (CTS) framework. We adopt the BSSN formulation for evolving the metric and a high-resolution shock-capturing scheme to handle the magnetohydrodynamics. Our simulations of unmagnetized binaries agree with the results of Shibata, Taniguchi and Uryū [M. Shibata, K. Taniguchi, and K. Uryū, Phys. Rev. D 68, 084020 (2003).]. In cases in which the mergers result in a prompt collapse to a black hole, we are able to use puncture gauge conditions to extend the evolution and determine the mass of the material that forms a disk. We find that the disk mass is less than 2% of the total mass in all cases studied. We then add a small poloidal magnetic field to the initial configurations and study the subsequent evolution. For cases in which the remnant is a hypermassive neutron star, we see measurable differences in both the amplitude and phase of the gravitational waveforms following the merger. For cases in which the remnant is a black hole surrounded by a disk, the disk mass and the gravitational waveforms are about the same as the unmagnetized cases. Magnetic fields substantially affect the long-term, secular evolution of a hypermassive neutron star (driving “delayed collapse”) and an accretion disk around a nascent black hole.

It has been argued that the quantum (conformal) trace anomaly could potentially provide us with a dynamical explanation of the cosmological constant problem. In this paper, however, we show by means of a semiclassical analysis that the trace anomaly does not affect the cosmological constant. We construct the effective action of the conformal anomaly for flat Friedmann-Lemaître-Robertson-Walker spacetimes consisting of local quadratic geometric curvature invariants. Counterterms are thus expected to influence the numerical value of the coefficients in the trace anomaly and we must therefore allow these parameters to vary. We calculate the evolution of the Hubble parameter in quasi-de Sitter spacetime, where we restrict our Hubble parameter to vary slowly in time, and in Friedmann-Lemaître-Robertson-Walker spacetimes. We show dynamically that a universe consisting of matter with a constant equation of state, a cosmological constant, and the quantum trace anomaly evolves either to the classical de Sitter attractor or to a quantum trace anomaly driven one. When considering the trace anomaly truncated to quasi-de Sitter spacetime, we find a region in parameter space where the quantum attractor destabilizes. When considering the exact expression of the trace anomaly, a stability analysis shows that whenever the trace anomaly driven attractor is stable, the classical de Sitter attractor is unstable, and vice versa. Semiclassically, the trace anomaly does not affect the classical late time de Sitter attractor, and hence it does not solve the cosmological constant problem.

The vector mesons in three-flavor quark matter with chiral and diquark condensates are studied using the in-medium QCD sum rules. The diquark condensate leads to a mass splitting between the flavor-octet and flavor-singlet channels. At high density, the singlet vector meson disappears from the low-energy spectrum, while the octet vector mesons survive as light excitations with a mass comparable to the fermion gap. A possible connection between the light gluonic modes and the flavor-octet vector mesons at high density is also discussed.

It can be expected that the respective endpoints of the Gregory-Laflamme black brane instability and the Rayleigh-Plateau membrane instability are related because the bifurcation diagrams of the black hole–black string system and the liquid drop–liquid bridge system display many similarities. In this paper, I investigate the nonlinear dynamics of the Rayleigh-Plateau instability in a range of dimensions, including the critical dimension at which the phase structure changes. I show that near the critical dimension and above, depending on a parameter in initial conditions an unstable cylinder will either pinch off or converge to an equilibrium state. The equilibrium state is apparently nonuniform but has a constant mean curvature everywhere. The results suggest that in the gravity side, near the critical dimension and above, the final state of an unstable black string (which is not too long) is a nonuniform black string. The equation of motion adopted to describe the dynamics is the surface diffusion equation, which was originally proposed to describe a grooving process of heated metal surfaces. An interesting correspondence between the diffusion dynamics and black hole (thermo)dynamics is discussed.

We study nonperturbative moduli superpotentials with positive exponents, i.e. the form like $A{e}^{aT}$ with a positive constant $a$ and the modulus $T$. These effects can be generated, e.g., by D-branes which have negative Ramond-Ramond charge of the lower-dimensional D-brane. The scalar potentials including such terms have quite a rich structure. There are several local minima with different potential energies and a high barrier, whose height is of $\mathcal{O}(M_p^4)$. We discuss their implications from the viewpoints of cosmology and particle phenomenology, e.g. the realization of inflation models, avoiding the overshooting problem. This type of potential would be useful to realize the inflation and low-energy supersymmetry breaking.

The condition for the existence of a bound state between two fermions exchanging massive scalars is derived. For low scalar mass, we reproduce the scalar field model result. The high scalar mass result exhibits a somewhat different inequality condition.

We study the twisted Hopf-algebra symmetries of observer-independent canonical spacetime noncommutativity, for which the commutators of the spacetime coordinates take the form $[{\widehat{x}}^{\mu },{\widehat{x}}^{\nu }]=i{\theta }^{\mu \nu }$ with observer-independent (and coordinate-independent) ${\theta }^{\mu \nu }$. We find that it is necessary to introduce nontrivial commutators between transformation parameters and spacetime coordinates, and that the form of these commutators implies that all symmetry transformations must include a translation component. We show that with our noncommutative transformation parameters the Noether analysis of the symmetries is straightforward, and we compare our canonical-noncommutativity results with the structure of the conserved charges and the “no-pure-boost” requirement derived in a previous study of $\kappa$-Minkowski noncommutativity. We also verify that, while at intermediate stages of the analysis we do find terms that depend on the ordering convention adopted in setting up the Weyl map, the final result for the conserved charges is reassuringly independent of the choice of Weyl map and (the corresponding choice of) star product.

The absorption cross section of Reissner-Nordström black holes for the electromagnetic field is computed numerically for arbitrary frequencies. The numerical results are in excellent agreement with the low- and high-frequency limits, which are obtained with analytical methods. Special emphasis is given to the extreme Reissner-Nordström black hole case.

The lightest neutralino in the minimal supersymmetric extension of the standard model can be, in principle, massless. If superlight neutralinos are the dark matter, structure formation constrains their mass to be above a few keV. I show that relaxing the assumption of radiation domination and entropy conservation prior to big bang nucleosynthesis, the relic abundance of very light neutralinos can be consistent with the inferred cold dark matter density. I study how one can hunt for light neutralino dark matter, with a mass at or below a GeV, focusing on both direct and indirect searches. I argue that the two most promising channels are spin-dependent direct detection and the search for monochromatic gamma rays from the prompt pair-annihilation of neutralinos into photons with GLAST. My study indicates that the lightest lightest neutralinos can be detected as long as their mass is above a few tenth of a GeV, a mass range where a future linear collider could provide important information on the details of the particle dark matter model.

The Pierre Auger Collaboration has reported a correlation between ultrahigh energy cosmic rays (UHECR) and nearby active galactic nuclei (AGN) within $\sim 75\mathrm{Mpc}$. Two of these events fall within 3 degrees from Centaurus A (Cen A), the nearest AGN, clearly suggesting that this object is a strong UHECR emitter. Here we pursue this hypothesis and forecast the expected rate of ultrahigh energy neutrinos in detectors like IceCube. In our baseline model we find a rate of $\sim 0.4–0.6{\mathrm{yr}}^{-1}$ events above a threshold of 100 TeV, the uncertainty of which is mainly related to the poor knowledge of the physical parameters of the source and details of the model. This situation will improve with detailed high energy gamma ray measurements of Cen A by the upcoming Gamma Ray Large Area Space Telescope (GLAST) satellite. This would make Cen A the first example where the potential of high energy multimessenger astronomy is finally realized.

Large scale peculiar velocity (LSPV) is a crucial probe of dark matter, dark energy, and gravity at cosmological scales. However, its application is severely limited by measurement obstacles. We show that fluctuations in type Ia supernovae fluxes induced by LSPV offer a promising approach to measure LSPV at intermediate redshifts. In the 3D Fourier space, gravitational lensing, the dominant systematical error, is well suppressed, localized, and can be further corrected effectively. Advances in supernova observations can further significantly reduce shot noise induced by supernova intrinsic fluctuations, which is the dominant statistical error. Robust mapping on the motion of the dark universe through type Ia supernovae is thus feasible to $z\sim 0.5$.

Gamma-ray bursts (GRBs) are one of the candidates of ultrahigh-energy ($\gtrsim {10}^{18.5}\mathrm{eV}$) cosmic-ray (UHECR) sources. We investigate high-energy cosmic-ray acceleration including heavy nuclei in GRBs by using Geant 4, and discuss its various implications, taking both high-luminosity (HL) and low-luminosity (LL) GRBs into account. This is because LL GRBs may also make a significant contribution to the observed UHECR flux if they form a distinct population. We show that not only protons, but also heavier nuclei can be accelerated up to ultrahigh energies in the internal, (external) reverse, and forward shock models. We also show that the condition for ultrahigh-energy heavy nuclei such as iron to survive is almost the same as that for $\sim \mathrm{TeV}$ gamma rays to escape from the source and for high-energy neutrinos not to be much produced. The multimessenger astronomy by neutrino and GeV-TeV gamma-ray telescopes such as IceCube and KM3Net, GLAST and MAGIC will be important to see whether GRBs can be accelerators of ultrahigh-energy heavy nuclei. We also demonstrate expected spectra of high-energy neutrinos and gamma rays, and discuss their detectabilities. In addition, we discuss implications of the GRB-UHECR hypothesis. We point out, since the number densities of HL GRBs and LL GRBs are quite different, its determination by UHECR observations is also important.

The possible influence of primordial black hole (PBH) evaporations on cosmic microwave backgrounds (CMB) is investigated. The spectrum distortions of CMB from the blackbody spectrum are described by the chemical potential $\mu$ and the Compton parameter $y$. From COBE/FIRAS limits on $\mu$ and $y$, the power-law index $n$ of primordial density fluctuations and the mass fraction of PBHs $\beta$ are constrained by employing the peak theory for the formation process of PBHs. Constraints set here are $n<1.304$ and $n<1.333$ in the thresholds of peaks ${\zeta }_{\mathrm{th}}=0.7$ and ${\zeta }_{\mathrm{th}}=1.2$, respectively, for the PBH mass range between $2.7\times {10}^{11}\mathrm{g}$ and $1.6\times {10}^{12}\mathrm{g}$, and $n<1.312$ and $n<1.343$ in the thresholds of peaks ${\zeta }_{\mathrm{th}}=0.7$ and ${\zeta }_{\mathrm{th}}=1.2$, respectively, for the PBH mass range between $1.6\times {10}^{12}\mathrm{g}$ and $3.5\times {10}^{13}\mathrm{g}$, which correspond to the comoving scales between $3\times {10}^{-18}\mathrm{Mpc}$ and $4\times {10}^{-17}\mathrm{Mpc}$. The constraint on the PBH fraction, which is the direct probe of the amplitude of density fluctuations on these scales, stays at almost the same value as $\beta <{10}^{-21}$ in these mass ranges. It is also found that, with these constraints, UV photons injected by PBH evaporations are unlikely to ionize the majority of hydrogen atoms.

The $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0{\pi }^0$ reaction cross section as a function of the incident energy is calculated using a model that is an extension of our recently published model of the $e^{+}{e}^{-}$ annihilation into four charged pions. The latter considered the intermediate states with the $\pi$, $\rho$, and $a_1$ mesons and fixed the mixing angle of the $a_1\rho \pi$ Lagrangian and other parameters by fitting the cross section data. Here we supplement the original intermediate states with those containing $\omega (782)$ and $h_1(1170)$, but keep unchanged the values of those parameters that enter both charged and mixed channel calculations. The inclusion of $\omega$ is vital for obtaining a good fit to the cross section data, while the intermediate states with $h_1$ further improve it. Finally, we merge our models of the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0{\pi }^0$ and $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^{+}{\pi }^{-}$ reactions and obtain a simultaneous good fit.

The transition form factors of $B_{(s)}\to S$, with $S$ denoting a scalar meson, are investigated in the light-cone sum rules approach. The numerical values are approximately twice the number estimated in the light-front quark model and QCD sum rules approach. Using these form factors, we present the analysis of the decay rates for $B\to a_0(1450)l{\overline{\nu }}_l$, $B\to K_0^{*}(1430)l\overline{l}$, $B_s\to K_0^{*}(1430)l{\overline{\nu }}_l$, and $B_s\to f_0(1500)l\overline{l}$ with $l=e$, $\mu$, $\tau$. The results indicate that magnitudes of $BR({\overline{B}}_0\to a_0(1450)l{\overline{\nu }}_l)$ and $BR(B_s\to K_0^{*}(1430)l{\overline{\nu }}_l)$ arrive at the order of ${10}^{-4}$, which can be measured in future experiments to clarify the inner structure of scalar mesons. It is also observed that $BR(B\to K_0^{*}(1430){\tau }^{+}{\tau }^{-})$ and $BR(B_s\to f_0(1500){\tau }^{+}{\tau }^{-})$ are an order of magnitude smaller than the corresponding channels of $e^{+}{e}^{-}$ and ${\mu }^{+}{\mu }^{-}$ final states due to the heavily suppressed phase space. Moreover, the longitudinal lepton polarization asymmetry for $B\to K_0^{*}(1430)l\overline{l}$ and $B_s\to f_0(1500)l\overline{l}$ are also investigated, whose values are close to $-1$ for the $e^{+}{e}^{-}$ and ${\mu }^{+}{\mu }^{-}$ pair except for the region close to the endpoints.

In this paper we propose a new method for calculating the response of the quark condensate to the chemical potential. Based on the method of calculating the dressed-quark propagator at finite chemical potential in the framework of the rainbow-ladder approximation of the Dyson-Schwinger approach proposed in [H. S. Zong, L. Chang, F. Y. Hou, W. M. Sun, and Y. X. Liu, Phys. Rev. C 71, 015205 (2005).] and adopting the meromorphic form of the quark propagator given in [R. Alkofer, W. Detmold, C. S. Fischer, and P. Maris, Phys. Rev. D 70, 014014 (2004).][M. S. Bhagwat, M. A. Pichowsky, and P. C. Tandy, Phys. Rev. D 67, 054019 (2003).], the quark condensate at finite chemical potential $⟨\overline{q}q⟩[\mu ]$ is calculated analytically. The obtained expression for $⟨\overline{q}q⟩[\mu ]$ is real, which is different from the results in the previous literature. In addition, it is found that when the chemical potential $\mu$ is less than a critical one $⟨\overline{q}q⟩[\mu ]$ is kept unchanged from its vacuum value. A comparison is made between this behavior of the quark condensate and those reported in the previous literatures.

We derive a class of formulae relating moments of $B\to X_u\ell \overline{\nu }$ to $B\to X_s\gamma$ in the shape-function region, where $m_X^2\sim m_b{\Lambda }_{\mathrm{QCD}}$. We also derive an analogous class of formulae involving the decay $B\to X_s{\ell }^{+}{\ell }^{-}$. These results incorporate ${\Lambda }_{\mathrm{QCD}}/m_b$ power corrections, but are independent of leading and subleading hadronic shape functions. Consequently, they enable one to determine $|V_{ub}|/|V_{tb}{V}_{ts}^{*}|$ to subleading order in a model-independent way.

We analyze the electromagnetic scattering of massive particles with and without spin wherein one particle (or both) is electrically neutral. Using the techniques of effective field theory, we isolate the leading long distance effects, both classical and quantum mechanical. For spinless systems results are identical to those obtained earlier via more elaborate dispersive methods. However, we also find new results if either or both particles carry spin.

We present a search for the decays $B^{+}\to {\pi }^{+}{\ell }^{+}{\ell }^{-}$ and $B^0\to {\pi }^0{\ell }^{+}{\ell }^{-}$, where ${\ell }^{+}{\ell }^{-}$ is either a ${\mu }^{+}{\mu }^{-}$ or $e^{+}{e}^{-}$ pair, with a data sample of $657\times {10}^6$ $B\overline{B}$ pairs collected with the Belle detector at the KEKB $e^{+}{e}^{-}$ collider. Signal events are reconstructed from a charged or a neutral pion candidate and a pair of oppositely charged electrons or muons. No significant signal is observed and we set an upper limit on the isospin-averaged branching fraction $\mathcal{B}(B\to \pi {\ell }^{+}{\ell }^{-})<6.2\times {10}^{-8}$ at the 90% confidence level.