1,032 research outputs found

    Spontaneous CP Symmetry Breaking at the Electroweak Scale

    Full text link
    We present a top-condensation model in which the CP symmetry is spontaneously broken at the electroweak scale due to the condensation of two composite Higgs doublets. In particular the CP-violating phase of the CKM matrix is generated. A simpler model where only one quark family is included is also discussed. In this case, for a general four-fermion interaction (Gtb0G_{tb}\neq 0), the particle spectrum is the one of the one Higgs doublet model.Comment: 25 pages, LaTeX. References and comment adde

    Neutrinos in IceCube/KM3NeT as probes of Dark Matter Substructures in Galaxy Clusters

    Full text link
    Galaxy clusters are one of the most promising candidate sites for dark matter annihilation. We focus on dark matter with mass in the range 10 GeV - 100 TeV annihilating to muon pairs, neutrino pairs, top pairs, or two neutrino pairs, and forecast the expected sensitivity to the annihilation cross section into these channels by observing galaxy clusters at IceCube/KM3NeT. Optimistically, the presence of dark matter substructures in galaxy clusters is predicted to enhance the signal by 2-3 orders of magnitude over the contribution from the smooth component of the dark matter distribution. Optimizing for the angular size of the region of interest for galaxy clusters, the sensitivity to the annihilation cross section of heavy DM with mass in the range 300 GeV - 100 TeV will be of the order of 10^{-24} cm^3 s^{-1}, for full IceCube/KM3NeT live time of 10 years, which is about one order of magnitude better than the best limit that can be obtained by observing the Milky Way halo. We find that neutrinos from cosmic ray interactions in the galaxy cluster, in addition to the atmospheric neutrinos, are a source of background. We show that significant improvement in the experimental sensitivity can be achieved for lower DM masses in the range 10 GeV - 300 GeV if neutrino-induced cascades can be reconstructed to approximately 5 degrees accuracy, as may be possible in KM3NeT. We therefore propose that a low-energy extension "KM3NeT-Core", similar to DeepCore in IceCube, be considered for an extended reach at low DM masses.Comment: v2: 17 pages, 5 figures. Neutrino spectra corrected, dependence on dark matter substructure model included, references added. Results unchanged. Accepted in PR

    Cosmic superstring trajectories in warped compactifications

    Full text link
    We explore the generic motion of cosmic (super)strings when the internal compact dimensions are warped, using the Klebanov-Strassler solution as a prototypical throat geometry. We find that there is no dynamical mechanism which localises the string at the tip of the throat, but rather that the motion seems to explore both internal and external degrees of freedom democratically. This indicates that cosmic (super)strings formed by inflationary brane-antibrane annihilation will have sufficient internal motion for the gravitational wave signals from the string network to be suppressed relative to the signal from a `standard' cosmic string network.Comment: 31 pages, 8 figure

    Sequestering the standard model vacuum energy

    Get PDF
    We propose a very simple reformulation of general relativity, which completely sequesters from gravity all of the vacuum energy from a matter sector, including all loop corrections and renders all contributions from phase transitions automatically small. The idea is to make the dimensional parameters in the matter sector functionals of the 4-volume element of the Universe. For them to be nonzero, the Universe should be finite in spacetime. If this matter is the standard model of particle physics, our mechanism prevents any of its vacuum energy, classical or quantum, from sourcing the curvature of the Universe. The mechanism is consistent with the large hierarchy between the Planck scale, electroweak scale, and curvature scale, and early Universe cosmology, including inflation. Consequences of our proposal are that the vacuum curvature of an old and large universe is not zero, but very small, that w DE ≃−1 is a transient, and that the Universe will collapse in the future

    HyRec: A fast and highly accurate primordial hydrogen and helium recombination code

    Get PDF
    We present a state-of-the-art primordial recombination code, HyRec, including all the physical effects that have been shown to significantly affect recombination. The computation of helium recombination includes simple analytic treatments of hydrogen continuum opacity in the He I 2 1P - 1 1S line, the He I] 2 3P - 1 1S line, and treats feedback between these lines within the on-the-spot approximation. Hydrogen recombination is computed using the effective multilevel atom method, virtually accounting for an infinite number of excited states. We account for two-photon transitions from 2s and higher levels as well as frequency diffusion in Lyman-alpha with a full radiative transfer calculation. We present a new method to evolve the radiation field simultaneously with the level populations and the free electron fraction. These computations are sped up by taking advantage of the particular sparseness pattern of the equations describing the radiative transfer. The computation time for a full recombination history is ~2 seconds. This makes our code well suited for inclusion in Monte Carlo Markov chains for cosmological parameter estimation from upcoming high-precision cosmic microwave background anisotropy measurements.Comment: Version accepted by PRD. Numerical integration switches adapted to be well behaved for a wide range of cosmologies (Sec. V E). HyRec is available at http://www.tapir.caltech.edu/~yacine/hyrec/hyrec.htm

    Sequestering effects on and of vacuum decay

    Get PDF
    We consider phase transitions and their contributions to vacuum energy in the manifestly local theory of vacuum energy sequestering. We demonstrate that the absence of instabilities imposes constraints on the couplings of gravitating and nongravitating sectors, which can be satisfied in a large class of models. We further show by explicit construction that the vacuum energy contributions to the effective cosmological constant in the descendant vacua are generically strongly suppressed by the ratios of space-time volumes of parent and descendant geometries. This means that the cosmological constant in de Sitter descendant vacua remains insensitive to phase transitions which may have occurred in the course of its cosmic history

    Massive vector fields on the Schwarzschild spacetime: quasinormal modes and bound states

    Full text link
    We study the propagation of a massive vector or Proca field on the Schwarzschild spacetime. The field equations are reduced to a one-dimensional wave equation for the odd-parity part of the field and two coupled equations for the even-parity part of the field. We use numerical techniques based on solving (scalar or matrix-valued) three-term recurrence relations to compute the spectra of both quasi-normal modes and quasi-bound states, which have no massless analogue, complemented in the latter case by a forward-integration method. We study the radial equations analytically in both the near-horizon and far-field regions and use a matching procedure to compute the associated spectra in the small-mass limit. Finally, we comment on extending our results to the Kerr geometry and its phenomenological relevance for hidden photons arising e.g. in string theory compactifications.Comment: 15 pages, 8 figures; minor corrections, to be published in Phys. Rev.

    The Cosmological Evolution of Domain Wall Networks

    Full text link
    We have studied the cosmological evolution of domain wall networks in two, three and four spatial dimensions using high-resolution field theory simulations. The dynamical range and number of our simulations is larger than in previous works, but does not allow us to exclude previous hints of deviations to the naively expected scale-invariant evolution. These results therefore suggest that the approach of domain wall networks to linear scaling is a much slower process than that of cosmic strings, which has been previously characterized in detail.Comment: 7 pages, submitted to Phys Rev

    On the theory of the propagation of detonation in gaseous systems

    Get PDF
    The existing theory of detonation is critically examined. It is shown that the considerations with which the steady value of the velocity of detonation is chosen are not convincing. In connection with the problem of the process of the chemical reaction in a detonation wave, the objections raised against the conceptions of Le Chatelier and Vieille of the 19th century with regard to the ignition of the gas by the shock wave are refuted. On the basis of this concept, it is possible to give a rigorous foundation for the existing method of computing the detonation velocity. The distributions of the temperature, the pressure, and the velocity in the detonation wave front as the chemical reaction proceeds, are considered. On the assumption of the absence of losses, the pure compression of the gas in the shock wave at the start of the chemical reaction develops a temperature that is near the temperature of combustion of the given mixture at constant pressure
    corecore