Strong decays of charmed baryons are analyzed in the framework of heavy hadron chiral perturbation theory (HHChPT) in which heavy quark symmetry and chiral symmetry are synthesized. HHChPT works excellently for describing the strong decays of $s$-wave charmed baryons. For $L=1$ orbitally excited states, two of the unknown couplings, namely, $h_2$ and $h_{10}$, are determined from the resonant ${\Lambda }_c^{+}\pi \pi$ mode produced in the ${\Lambda }_c(2593)$ decay and the width of ${\Sigma }_c(2800)$, respectively. Predictions for the strong decays of the $p$-wave charmed baryon states ${\Lambda }_c(2625)$, ${\Xi }_c(2790)$ and ${\Xi }_c(2815)$ are presented. Since the decay ${\Lambda }_c(2593{)}^{+}\to {\Lambda }_c^{+}\pi \pi$ receives nonresonant contributions, our value for $h_2$ is smaller than the previous estimates. We also discuss the first positive-parity excited charmed baryons. We conjecture that the charmed baryon ${\Lambda }_c(2880)$ with $J^P=\frac{5}{2}\genfrac{}{}{0ex}{}{+}{}$ is an admixture of ${\Lambda }_{c2}(\frac{5}{2}\genfrac{}{}{0ex}{}{+}{})$ with an ${\tilde{\Lambda }}_{c3}^{\prime \prime }(\frac{5}{2}\genfrac{}{}{0ex}{}{+}{})$; both are $L=2$ orbitally excited states. The potential model suggests $J^P=\frac{5}{2}\genfrac{}{}{0ex}{}{-}{}$ or $\frac{3}{2}\genfrac{}{}{0ex}{}{+}{}$ for ${\Lambda }_c(2940{)}^{+}$. Measurements of the ratio of ${\Sigma }_c^{*}\pi /{\Sigma }_c\pi$ will enable us to discriminate the $J^P$ assignments for ${\Lambda }_c(2940)$. We advocate that the $J^P$ quantum numbers of ${\Xi }_c(2980)$ and ${\Xi }_c(3077)$ are $\frac{1}{2}\genfrac{}{}{0ex}{}{+}{}$ and $\frac{5}{2}\genfrac{}{}{0ex}{}{+}{}$, respectively. Under this $J^P$ assignment, it is easy to understand why ${\Xi }_c(2980)$ is broader than ${\Xi }_c(3077)$.

We study the three-body charmed baryonic decays ${\overline{B}}^0\to {\Sigma }_c^{++}\overline{p}{\pi }^{-}$ and ${\overline{B}}^0\to {\Sigma }_c^0\overline{p}{\pi }^{+}$ in the four-body final state ${\overline{B}}^0\to {\Lambda }_c^{+}\overline{p}{\pi }^{+}{\pi }^{-}$, using a data sample of $357{\mathrm{fb}}^{-1}$ accumulated at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We measure the branching fractions $\mathcal{B}({\overline{B}}^0\to {\Sigma }_c(2455{)}^{++}\overline{p}{\pi }^{-})=(2.1\pm 0.2\pm 0.3\pm 0.5)\times {10}^{-4}$, $\mathcal{B}({\overline{B}}^0\to {\Sigma }_c(2455{)}^0\overline{p}{\pi }^{+})=(1.4\pm 0.2\pm 0.2\pm 0.4)\times {10}^{-4}$ and $\mathcal{B}({\overline{B}}^0\to {\Sigma }_c(2520{)}^{++}\overline{p}{\pi }^{-})=(1.2\pm 0.1\pm 0.2\pm 0.3)\times {10}^{-4}$ with signal significances of $13.1\sigma$, $9.4\sigma$ and $7.1\sigma$, respectively. The errors are statistical, systematic, and due to the uncertainty in $\mathcal{B}({\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+})$, respectively. We also set an upper limit $\mathcal{B}({\overline{B}}^0\to {\Sigma }_c(2520{)}^0\overline{p}{\pi }^{+})<0.38\times {10}^{-4}$ at the 90% confidence level. In addition, we obtain a nonresonant branching fraction of $(6.4\pm 0.4\pm 0.9\pm 1.7)\times {10}^{-4}$, and a total branching fraction of $(11.2\pm 0.5\pm 1.4\pm 2.9)\times {10}^{-4}$ for ${\overline{B}}^0\to {\Lambda }_c^{+}\overline{p}{\pi }^{+}{\pi }^{-}$.

The primordial perturbations of test scalar fields not affecting the evolution of background may be very interesting since they can be transferred to the curvature perturbations by some mechanisms, and thus under certain condition can be responsible for the structure formation of observable universe. In this brief report we study the primordial perturbations of test scalar fields in various (super)accelerated expanding backgrounds.

The physical process version and the equilibrium state version of the first law of black ring thermodynamics in $n$-dimensional Einstein gravity with Chern-Simons term were derived. This theory constitutes the simplest generalization of the five-dimensional one admitting a stationary black ring solution. The equilibrium state version of the first law of black ring mechanics was achieved by choosing any cross section of the event horizon to the future of the bifurcation surface.

We consider in more detail the covariant counterterm proposed by Mann and Marolf in asymptotically flat spacetimes. With an eye to specific practical computations using this counterterm, we present explicit expressions in general $d$ dimensions that can be used in the so-called “cylindrical cutoff” to compute the action and the associated conserved quantities for an asymptotically flat spacetime. As applications, we show how to compute the action and the conserved quantities for the NUT-charged spacetime and for the Kerr black hole in four dimensions.

The accuracy and stability of the Caltech-Cornell pseudospectral code is evaluated using the Kidder, Scheel, and Teukolsky (KST) representation of the Einstein evolution equations. The basic “Mexico City tests” widely adopted by the numerical relativity community are adapted here for codes based on spectral methods. Exponential convergence of the spectral code is established, apparently limited only by numerical roundoff error or by truncation error in the time integration. A general expression for the growth of errors due to finite machine precision is derived, and it is shown that this limit is achieved here for the linear plane-wave test.

We have previously shown that spherically symmetric, inhomogeneous universe models can explain both the supernova data and the location of the first peak in the spectrum of the cosmic microwave background (CMB) without resorting to dark energy. In this work, we investigate whether it is possible to get an even better fit to the supernova data by allowing the observer to be positioned away from the origin in the spherically symmetric coordinate system. In such a scenario, the observer sees an anisotropic relation between redshifts and the luminosity distances of supernovae. The level of anisotropy allowed by the data will then constrain how far away from the origin the observer can be located, and possibly even allow for a better fit. Our analysis shows that the fit is indeed improved, but not by a significant amount. Furthermore, we find that the supernova data do not place a rigorous constraint on how far off-center the observer can be located.

We consider a Randall-Sundrum two-brane cosmological model in the low energy gradient expansion approximation by Kanno and Soda. It is a scalar-tensor theory with a specific coupling function and a specific potential. Upon introducing the Friedmann-Lemaître-Robertson-WalkerFLRW metric and perfect fluid matter on both branes in the Jordan frame, the effective dynamical equation for the $A$-brane (our Universe) scale factor decouples from the scalar field and $B$-brane matter leaving only a nonvanishing integration constant (the dark radiation term). We find exact solutions for the $A$-brane scale factor for four types of matter: cosmological constant, radiation, dust, and cosmological constant plus radiation. We perform a complementary analysis of the dynamics of the scalar field (radion) using phase space methods and examine convergence towards the limit of general relativity. In particular, we find that radion stabilizes at a certain finite value for suitable negative matter densities on the $B$-brane. Observational constraints from solar system experiments (PPN) and primordial nucleosynthesis (BBN) are also briefly discussed.

We investigate the effect of a coupling between dark matter and dark energy on the rates for the direct detection of dark matter. The magnitude of the effect depends on the strength $\kappa$ of this new interaction relative to gravity. The resulting isothermal velocity distribution for dark matter in galaxy halos is still Maxwell-Boltzmann (M-B), but the characteristic velocity and the escape velocity are increased by $\sqrt{1+{\kappa }^2}$. We adopt a phenomenological approach and consider values of $\kappa$ near unity. For such values we find that: (i) The (time averaged) event rate increases for light WIMPs, while it is somewhat reduced for WIMP masses larger than 100 GeV. (ii) The time dependence of the rate arising from the modulation amplitude is decreased compared to the standard M-B velocity distribution. (iii) The average and maximum WIMP energy increase proportionally to $1+{\kappa }^2$, which, for sufficiently massive WIMPs, allows the possibility of designing experiments measuring $\gamma$ rays following nuclear de-excitation.

We study top quark flavor violation in the framework of a warped extra dimension with the Standard Model (SM) fields propagating in the bulk. Such a scenario provides solutions to both the Planck-weak hierarchy problem and the flavor puzzle of the SM without inducing a flavor problem. We find that, generically, $tcZ$ couplings receive a huge enhancement, in particular, the right-handed ones can be $\mathcal{O}(1\%)$. This results in $\mathrm{BR}(t\to cZ)$ at or above the sensitivity of the Large Hadron Collider (LHC). At the International Linear Collider (ILC), single top production, via $e^{+}{e}^{-}\to t\overline{c}$, can be a striking signal for this scenario. In particular, it represents a physics topic of critical importance that can be explored even with a relatively low energy option, close to the $tc$ threshold. At both the LHC and the ILC, angular distributions can probe the above prediction of dominance of right-handed couplings.

We use QCD spectral sum rules to test the nature of the meson $X(3872)$, assumed to be an exotic four-quark ($c\overline{c}q\overline{q}$) state with $J^{\mathrm{PC}}=1^{++}$. For definiteness, we work with the diquark-antidiquark current proposed recently, at leading order in ${\alpha }_s$, consider the contributions of higher dimension condensates and keep terms which are linear in the light quark mass $m_q$. We find $M_X=(3925\pm 127)\mathrm{MeV}$ which is compatible, within the errors, with the experimental candidate $X(3872)$, while the SU(3) breaking-terms lead to an unusual mass-splitting $M_{X^s}-M_X=-(61\pm 30)\mathrm{MeV}$. The mass-difference between the neutral states due to isospin violation is about $(2.6\sim 3.9)\mathrm{MeV}$. For the $b$-quark, we predict $M_{X_b}=(10144\pm 106)\mathrm{MeV}$ for the $X_b(b\overline{b}q\overline{q})$, which is much below the $\overline{B}{B}^{*}$ threshold, and for the $X_b^s(b\overline{b}s\overline{s})$, a mass-splitting $M_{X_b^s}-M_{X_b}=-(121\pm 182)\mathrm{MeV}$. Our analysis also indicates that the mass-splitting between the ground state and the radial excitation of about $(225\sim 250)\mathrm{MeV}$ is much smaller than in the case of ordinary mesons and is (within the errors) flavor-independent. We also extract the decay constants, analogous to $f_{\pi }$, of such mesons, which are useful for further studies of their leptonic and hadronic decay widths. The uncertainties of our estimates are mainly due to the ones from the $c$ and $b$ quark masses.

A search of neutrino magnetic moments was carried out at the Kuo-Sheng nuclear power station at a distance of 28 m from the 2.9 GW reactor core. With a high purity germanium detector of mass 1.06 kg surrounded by scintillating NaI(Tl) and CsI(Tl) crystals as anti-Compton detectors, a detection threshold of 5 keV and a background level of $1{\mathrm{kg}}^{-1}{\mathrm{keV}}^{-1}{\mathrm{day}}^{-1}$ near threshold were achieved. Details of the reactor neutrino source, experimental hardware, background understanding, and analysis methods are presented. Based on 570.7 and 127.8 days of Reactor ON and OFF data, respectively, at an average Reactor ON electron antineutrino flux of $6.4\times {10}^{12}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$, the limit on the neutrino magnetic moments of ${\mu }_{{\overline{\nu }}_{\mathrm{e}}}<7.4\times {10}^{-11}{\mu }_{\mathrm{B}}$ at 90% confidence level was derived. Indirect bounds on the ${\overline{\nu }}_{\mathrm{e}}$ radiative decay lifetimes were inferred.

We study the effect of a thermal quark mass, $m_T$, on the chiral phase transition and mesonic excitations in the light quark sector at finite temperature in a simple chirally symmetric model. We show that, while nonzero $m_T$ lowers the chiral condensate, the chiral transition remains of second order. It is argued that the mesonic excitations have a large decay rate at energies below $2m_T$, owing to the Landau damping of the quarks and the van Hove singularities of the collective modes.

One of the simplest time-dependent solutions of M theory consists of nine-dimensional Euclidean space times $1+1$-dimensional compactified Milne space-time. With a further modding out by $Z_2$, the space-time represents two orbifold planes which collide and re-emerge, a process proposed as an explanation of the hot big bang [J. Khoury, B. A. Ovrut, P. J. Steinhardt, and N. Turok, Phys. Rev. D 64, 123522 (2001).][P. J. Steinhardt and N. Turok, Science 296, 1436 (2002).][N. Turok, M. Perry, and P. J. Steinhardt, Phys. Rev. D 70, 106004 (2004).]. When the two planes are near, the light states of the theory consist of winding M2-branes, describing fundamental strings in a particular ten-dimensional background. They suffer no blue-shift as the M theory dimension collapses, and their equations of motion are regular across the transition from big crunch to big bang. In this paper, we study the classical evolution of fundamental strings across the singularity in some detail. We also develop a simple semiclassical approximation to the quantum evolution which allows one to compute the quantum production of excitations on the string and implement it in a simplified example.

One of the most exciting potential sources of gravitational waves for low-frequency, space-based gravitational wave (GW) detectors such as the proposed Laser Interferometer Space Antenna (LISA) is the inspiral of compact objects into massive black holes in the centers of galaxies. The detection of waves from such “extreme mass ratio inspiral” systems (EMRIs) and extraction of information from those waves require template waveforms. The systems’ extreme mass ratio means that their waveforms can be determined accurately using black hole perturbation theory. Such calculations are computationally very expensive. There is a pressing need for families of approximate waveforms that may be generated cheaply and quickly but which still capture the main features of true waveforms. In this paper, we introduce a family of such kludge waveforms and describe ways to generate them. Different kinds of kludges have already been used to scope out data analysis issues for LISA. The models we study here are based on computing a particle’s inspiral trajectory in Boyer-Lindquist coordinates, and subsequent identification of these coordinates with flat-space spherical polar coordinates. A gravitational waveform may then be computed from the multipole moments of the trajectory in these coordinates, using well-known solutions of the linearised gravitational perturbation equations in flat space time. We compute waveforms using a standard slow-motion quadrupole formula, a quadrupole/octupole formula, and a fast-motion, weak-field formula originally developed by Press. We assess these approximations by comparing to accurate waveforms obtained by solving the Teukolsky equation in the adiabatic limit (neglecting GW backreaction). We find that the kludge waveforms do extremely well at approximating the true gravitational waveform, having overlaps with the Teukolsky waveforms of 95% or higher over most of the parameter space for which comparisons can currently be made. Indeed, we find these kludges to be of such high quality (despite their ease of calculation) that it is possible they may play some role in the final search of LISA data for EMRIs.

We investigate a new type of dark matter with couplings to ordinary matter naturally suppressed by at least 1 order of magnitude compared to weak interactions. Despite the extra-weak interactions massive particles of this type (XWIMPs) can satisfy the Wilkinson Microwave Anisotropy Probe (WMAP) relic density constraints due to coannihilation if their masses are close to that of the lightest state of the minimal supersymmetric standard model (MSSM). The region in the parameter space of a suitably extended minimal supergravity model consistent with the WMAP3 constraints on XWIMPs is determined. Plots for sparticles’ masses are given which can be subject to test at the Large Hadron Collider. As an example for an explicit model we show that such a form of dark matter can arise in certain $Z^{\prime }$ extensions of the MSSM. Specifically, we consider an Abelian extension with spontaneous gauge symmetry breaking via Fayet-Iliopoulos $D$ terms in the hidden sector. The lightest supersymmetric particle of the full model arises from the extra $U(1{)}_X$ sector with extra-weak couplings to standard model particles due to experimental constraints. With $R$-parity conservation, the new XWIMP is a candidate for cold dark matter. In a certain limit the model reduces to the Stueckelberg extension of the MSSM without a Higgs mechanism, and wider ranges of models with similar characteristics are easy to construct.

Improved values for the two- and three-loop mass-dependent QED contributions to the anomalous magnetic moments of the electron, muon, and $\tau$ lepton are presented. The standard model prediction for the electron ($g-2$) is compared with its most precise recent measurement, providing a value of the fine-structure constant in agreement with a recently published determination. For the $\tau$ lepton, differences with previously published results are found and discussed.

A four-dimensional field theory with a qualitatively new type of nonlocality is constructed from a setting where Kaluza-Klein particles probe toroidally compactified string theory with twisted boundary conditions. In this theory fundamental particles are not pointlike and occupy a volume proportional to their $R$-charge. The theory breaks Lorentz invariance but appears to preserve spatial rotations. At low energies, it is approximately $N=4$ Super Yang-Mills theory, deformed by an operator of dimension seven. The dispersion relation of massless modes in vacuum is unchanged, but under certain conditions in this theory, particles can travel at superluminal velocities.

We consider a static circularly symmetric solution of three-dimensional Einstein equations with a negative cosmological constant (the BTZ black hole). The case of the zero cosmological constant corresponding to the interior region of a black hole is analyzed in detail. We prove that the maximally extended BTZ solution with the zero cosmological constant coincides with flat three-dimensional Minkowskian space-time without any singularities and horizons. The Euclidean version of this solution is shown to have a physical interpretation in the geometric theory of defects in solids describing combined wedge and screw dislocations.

We construct, numerically, a solution of the SU(2) Bogomolny equations corresponding to a sheet of BPS monopoles. It represents a domain wall between a vacuum region and a region of constant energy density, and it is the smoothed-out version of the planar sheet of Dirac monopoles obtained by linear superposition.