Constraints of the $\mathfrak{o}\mathfrak{s}\mathfrak{p}(6|4)$ symmetry on tree-level scattering amplitudes in $\mathcal{N}=6$ superconformal Chern-Simons theory are derived. Supplemented by Feynman diagram calculations, solutions to these constraints, namely, the four- and six-point superamplitudes, are presented and shown to be invariant under Yangian symmetry. This introduces integrability into the amplitude sector of the theory.

We explore possible cosmological consequences of a running Newton’s constant $G(\square )$, as suggested by the nontrivial ultraviolet fixed point scenario in the quantum field-theoretic treatment of Einstein gravity with a cosmological constant term. In particular, we focus here on what possible effects the scale-dependent coupling might have on large scale cosmological density perturbations. Starting from a set of manifestly covariant effective field equations derived earlier, we systematically develop the linear theory of density perturbations for a nonrelativistic, pressureless fluid. The result is a modified equation for the matter density contrast, which can be solved and thus provides an estimate for the growth index parameter $\gamma$ in the presence of a running $G$. We complete our analysis by comparing the fully relativistic treatment with the corresponding results for the nonrelativistic (Newtonian) case, the latter also with a weakly scale-dependent $G$.

Through a detailed numerical investigation in three spatial dimensions, we demonstrate that long-lived time-dependent field configurations emerge dynamically during symmetry breaking in an expanding de Sitter spacetime. We investigate two situations: a single scalar field with a double-well potential and an SU(2) non-Abelian Higgs model. For the single scalar, we show that large-amplitude oscillon configurations emerge spontaneously and persist to contribute about 1.2% of the energy density of the Universe. We also show that for a range of parameters, oscillon lifetimes are enhanced by the expansion and that this effect is a result of parametric resonance. For the SU(2) case, we see about 4% of the final energy density in oscillons.

We explore the stability properties of multifield solutions in the presence of a perfect fluid, as appropriate to assisted quintessence scenarios. We show that the stability condition for multiple fields ${\varphi }_i$ in identical potentials $V_i$ is simply $d^2{V}_i/d{\varphi }_i^2>0$, exactly as in the absence of a fluid. A possible new instability associated with the fluid is shown not to arise in situations of cosmological interest.

We analyze the creation of chameleons deep inside the Sun ($R\sim 0.7R_{\mathrm{sun}}$) and their subsequent conversion to photons near the magnetized surface of the Sun. We find that the spectrum of the regenerated photons lies in the soft x-ray region, hence addressing the solar corona problem. Moreover, these back-converted photons originating from chameleons have an intrinsic difference with regenerated photons from axions: their relative polarizations are mutually orthogonal before Compton interacting with the surrounding plasma. Depending on the photon-chameleon coupling and working in the strong coupling regime of the chameleons to matter, we find that the induced photon flux, when regenerated resonantly with the surrounding plasma, coincides with the solar flux within the soft x-ray energy range. Moreover, using the soft x-ray solar flux as a prior, we find that with a strong enough photon-chameleon coupling, the chameleons emitted by the Sun could lead to a regenerated photon flux in the CAST magnetic pipes, which could be within the reach of CAST with upgraded detector performance. Then, axion helioscopes have thus the potential to detect and identify particle candidates for the ubiquitous dark energy in the Universe.

We present the results of a global analysis of a class of models with an extended electroweak gauge group of the form $SU(2)\times SU(2)\times U(1)$, often denoted as $G(221)$ models, which include as examples the left-right, the leptophobic, the hadrophobic, the fermiophobic, the un-unified, and the nonuniversal models. Using an effective Lagrangian approach, we compute the shifts to the coefficients in the electroweak Lagrangian due to the new heavy gauge bosons, and obtain the lower bounds on the masses of the $Z^{\prime }$ and $W^{\prime }$ bosons. The analysis of the electroweak parameter bounds reveals a consistent pattern of several key observables that are especially sensitive to the effects of new physics and thus dominate the overall shape of the respective parameter contours.

We demonstrate that $\mu \leftrightarrow e$ slepton mixing is significantly more restricted than previously thought within the already remarkably flavor-safe $R$-symmetric supersymmetric standard model. We calculate bounds from $\mu \to e\gamma$, $\mu \to 3e$, and most importantly, $\mu \to e$ conversion. The process of $\mu \to e$ conversion is significantly more restrictive in $R$-symmetric models since this process can occur through operators that do not require a chirality flip. We delineate the allowed parameter space, demonstrating that maximal mixing is rarely possible with weak scale superpartners, while $\mathcal{O}(0.1)$ mixing is permitted within most of the space. The best approach to find or rule out $\mu \leftrightarrow e$ mixing in $R$-symmetric supersymmetric models is a multipronged attack looking at both $\mu \to e$ conversion as well as $\mu \to e\gamma$. The redundancy eliminates much of the parameter space where one process, but not both processes, contains amplitudes that accidentally destructively interfere. We briefly discuss implications for searches of slepton flavor violation at the LHC.

We present results concerning the nonperturbative evaluation of the ghost-gluon running QCD coupling constant from $N_f=2$ twisted-mass lattice calculations. A novel method for calibrating the lattice spacing, independent of the string tension and hadron spectrum, is presented with results in agreement with previous estimates. The value of ${\Lambda }_{\overline{\mathrm{MS}}}$ is computed from the running of the QCD coupling only after extrapolating to zero dynamical quark mass and after removing a nonperturbative operator-product expansion contribution that is assumed to be dominated by the dimension-two $⟨A^2⟩$ gluon condensate. The effect due to the dynamical quark mass in the determination of ${\Lambda }_{\overline{\mathrm{MS}}}$ is discussed.

We study lattice SU(2) Yang-Mills theory with dimension $d\ge 4$. The model can be expressed as a $(d-1)$-dimensional O(4) nonlinear $\sigma$ model in a $d$-dimensional heat bath. As is well known, the nonlinear $\sigma$ model alone shows a phase transition. If the quark confinement is a consequence of the absence of a phase transition for the Yang-Mills theory, then the fluctuations of the heat bath must destroy the long-range order of the nonlinear $\sigma$ model. In order to clarify whether this is true, we replace the fluctuations of the heat bath with Gaussian random variables, and obtain a Langevin equation which yields the effective action of the nonlinear $\sigma$ model by analyzing the Fokker-Planck equation. It turns out that the fluctuations indeed destroy the long-range order of the nonlinear $\sigma$ model within a mean-field approximation estimating a critical point, whereas for the corresponding U(1) gauge theory, the phase transition to the massless phase remains against the fluctuations.

The form factors of weak decays of the $B_c$ meson to orbitally excited charmonium, $D$, $B_s$, and $B$ mesons are calculated in the framework of the QCD-motivated relativistic quark model based on the quasipotential approach. Relativistic effects are systematically taken into account. The form factor dependence on the momentum transfer is reliably determined in the whole kinematical range. The form factors are expressed through the overlap integrals of the meson wave functions, which are known from the previous mass spectra calculations within the same model. On this basis, semileptonic and nonleptonic $B_c$ decay rates to orbitally excited heavy mesons are calculated. Predictions for the $B_c$ decays to the orbitally and radially excited $2P$ and $3S$ charmonium states are given, which could be used for clarifying the nature of the recently observed charmoniumlike states above the open charm production threshold.

The identification of the $X(3872)$ as a loosely-bound charm-meson molecule allows it to be described by an effective field theory, called XEFT, for the $D^{*}\overline{D}$, $D{\overline{D}}^{*}$, and $D\overline{D}\pi$ sector of QCD at energies small compared to the pion mass. We point out that this effective field theory can be extended to the sector that includes an additional pion and used to calculate cross sections for the scattering of a pion and the $X(3872)$. If the collision energy is much smaller than the pion mass, the cross sections are completely calculable at leading order in terms of the masses and widths of the charm mesons, pion masses, and the binding energy of the $X(3872)$. We carry out an explicit calculation of the cross section for the breakup of the $X(3872)$ into $D^{*+}{\overline{D}}^{*0}$ by the scattering of a very low energy ${\pi }^{+}$.

We study the first-order relativistic correction to the associated production of $J/\psi$ with light hadrons at $B$ factory experiments at $\sqrt{s}=10.58\mathrm{GeV}$, in the context of nonrelativistic QCD (NRQCD) factorization. We employ a strategy for NRQCD expansion that slightly deviates from the orthodox doctrine, in that the matching coefficients are not truly of a “short-distance” nature, but explicitly depend upon physical kinematic variables rather than partonic ones. Our matching method, with validity guaranteed by the Gremm-Kapustin relation, is particularly suited for the inclusive quarkonium production and decay processes with involved kinematics, exemplified by the process $e^{+}{e}^{-}\to J/\psi +gg$ considered in this work. Despite some intrinsic ambiguity affiliated with the order-$v^2$ NRQCD matrix element, if we choose its value as what has been extracted from a recent Cornell-potential-model-based analysis, including the relative order-$v^2$ effect is found to increase the lowest-order prediction for the integrated $J/\psi$ cross section by about 30%, and exert a modest impact on $J/\psi$ energy, angular and polarization distributions except near the very upper end of the $J/\psi$ energy. The order-$v^2$ contribution to the energy spectrum becomes logarithmically divergent at the maximum of $J/\psi$ energy. A consistent analysis may require that these large end-point logarithms be resummed to all orders in ${\alpha }_s$.

We measure the charge asymmetry $A$ of like-sign dimuon events in $6.1{\mathrm{fb}}^{-1}$ of $p\overline{p}$ collisions recorded with the D0 detector at a center-of-mass energy $\sqrt{s}=1.96\mathrm{TeV}$ at the Fermilab Tevatron collider. From $A$, we extract the like-sign dimuon charge asymmetry in semileptonic $b$-hadron decays: $A_{\mathrm{sl}}^b=-0.00957\pm 0.00251(\mathrm{stat})\pm 0.00146(\mathrm{syst})$. This result differs by 3.2 standard deviations from the standard model prediction $A_{\mathrm{sl}}^b(\mathrm{SM})=(-{2.3}_{-0.6}^{+0.5})\times {10}^{-4}$ and provides first evidence of anomalous $CP$ violation in the mixing of neutral $B$ mesons.

A phenomenological framework is presented for incorporating quantum gravity motivated corrections into the dynamics of spherically symmetric collapse. The effective equations are derived from a variational principle that guarantees energy conservation and the existence of a Birkhoff theorem. The gravitational potential can be chosen as a function of the areal radius to yield specific nonsingular static spherically symmetric solutions that generically have two horizons. For a specific choice of potential, the effective stress energy tensor violates only the dominant energy condition. The violations are maximum near the inner horizon and die off rapidly. A numerical study of the quantum corrected collapse of a spherically symmetric scalar field in this case reveals that the modified gravitational potential prevents the formation of a central singularity and ultimately yields a static, mostly vacuum, spacetime with two horizons. The matter “piles up” on the inner horizon giving rise to mass inflation at late times. The Cauchy horizon is transformed into a null, weak singularity, but in contrast to Einstein gravity, the absence of a central singularity renders this null singularity stable.

After recalling the basic concepts of gravity as an emergent phenomenon, we analyze the recent derivation of Newton’s law in terms of entropic force proposed by Verlinde. By reviewing some points of the procedure, we extend it to the case of a generic quantum gravity entropic correction to get compelling deviations to the Newton’s law. More specifically, we study: (1) noncommutative geometry deviations and (2) ungraviton corrections. As a special result in the noncommutative case, we find that the noncommutative character of the manifold would be equivalent to the temperature of a thermodynamic system. Therefore, in analogy to the zero temperature configuration, the description of spacetime in terms of a differential manifold could be obtained only asymptotically. Finally, we extend the Verlinde’s derivation to a general case, which includes all possible effects, noncommutativity, ungravity, asymptotically safe gravity, electrostatic energy, and extra dimensions, showing that the procedure is solid versus such modifications.

In this work we have derived a class of geometries which describe black holes and wormholes in Randall-Sundrum–type brane models, focusing mainly on asymptotically anti-de Sitter backgrounds. We show that by continuously deforming the usual four-dimensional vacuum background, a specific family of solutions is obtained. Maximal extensions of the solutions are presented, and their causal structures are discussed.

Several scenarios have been proposed in which the orbits of binary black holes enter the band of a gravitational wave detector with significant eccentricity. To avoid missing these signals or biasing parameter estimation it is important that we consider waveform models that account for eccentricity. The ingredients needed to compute post-Newtonian (PN) waveforms produced by spinning black holes inspiralling on quasi-eccentric orbits have been available for almost two decades at 2 PN order, and this work has recently been extended to 2.5 PN order. However, the computational cost of directly implementing these waveforms is high, requiring many steps per orbit to evolve the system of coupled differential equations. Here we employ the standard techniques of a separation of time scales and a generalized Keplerian parameterization of the orbits to produce efficient waveforms describing spinning black hole binaries with arbitrary masses and spins on quasi-eccentric orbits to 1.5 PN order. We separate the fast orbital time scale from the slow spin-orbit precession time scale by solving for the orbital motion in a noninterial frame of reference that follows the orbital precession. We outline a scheme for extending our approach to higher post-Newtonian order.

In recent work (Seljak, Hamaus, and Desjacques 2009) it was found that weighting central halo galaxies by halo mass can significantly suppress their stochasticity relative to the dark matter, well below the Poisson model expectation. This is useful for constraining relations between galaxies and the dark matter, such as the galaxy bias, especially in situations where sampling variance errors can be eliminated. In this paper we extend this study with the goal of finding the optimal mass-dependent halo weighting. We use $N$-body simulations to perform a general analysis of halo stochasticity and its dependence on halo mass. We investigate the stochasticity matrix, defined as $C_{ij}\equiv ⟨({\delta }_i-b_i{\delta }_m)({\delta }_j-b_j{\delta }_m)⟩$, where ${\delta }_m$ is the dark matter overdensity in Fourier space, ${\delta }_i$ the halo overdensity of the $i$-th halo mass bin, and $b_i$ the corresponding halo bias. In contrast to the Poisson model predictions we detect nonvanishing correlations between different mass bins. We also find the diagonal terms to be sub-Poissonian for the highest-mass halos. The diagonalization of this matrix results in one large and one low eigenvalue, with the remaining eigenvalues close to the Poisson prediction $1/\overline{n}$, where $\overline{n}$ is the mean halo number density. The eigenmode with the lowest eigenvalue contains most of the information and the corresponding eigenvector provides an optimal weighting function to minimize the stochasticity between halos and dark matter. We find this optimal weighting function to match linear mass weighting at high masses, while at the low-mass end the weights approach a constant whose value depends on the low-mass cut in the halo mass function. This weighting further suppresses the stochasticity as compared to the previously explored mass weighting. Finally, we employ the halo model to derive the stochasticity matrix and the scale-dependent bias from an analytical perspective. It is remarkably successful in reproducing our numerical results and predicts that the stochasticity between halos and the dark matter can be reduced further when going to halo masses lower than we can resolve in current simulations.

We study the spin-down of a neutron star during its early stages due to the neutrino emission. The mechanism we consider is the subsequent collisions of the produced neutrinos with the outer shells of the star. We find that this mechanism can indeed slow down the star rotation but only in the first tens of seconds of the core formation, which is when the appropriate conditions of flux and collision rate are met. We find that this mechanism can extract less than 1% of the star angular momentum, a result which is much less than previously estimated by other authors.

We compute time delays for gravitational lensing in a flat $\Lambda$ dominated cold dark matter Swiss cheese universe. We assume a primary and secondary pair of light rays are deflected by a single point mass condensation described by a Kottler metric (Schwarzschild with $\Lambda$) embedded in an otherwise homogeneous cosmology. We find that the cosmological constant’s effect on the difference in arrival times is nonlinear and at most around 0.002% for a large cluster lens; however, we find differences from time delays predicted by conventional linear lensing theory that can reach $\sim 4\%$ for these large lenses. The differences in predicted delay times are due to the failure of conventional lensing to incorporate the lensing mass into the mean mass density of the universe.