602043
Cosmological limits on deviations from phi2 potentials in oscillating scalar cold dark matter models.
We consider the consequences for oscillating scalar cold dark matter models of a scalar field phi which oscillates in a potential which deviates slightly from a phi2 potential. We consider a correction to the phi2 potential of the form Kphi2ln(phi2) + lambda(phi)phi4. Upper bounds on \K\ and \lambda)phi)\ are obtained as a function of the phi mass by requiring that the effects of the pressure introduced by the correction to the potential do not disrupt the conventional cold dark matter scenario for structure formation. The results are applied to some cosmological models of recent interest. In particular, it is shown that a scalar identified with the pseudo Goldstone boson of a U(1) symmetry explicitly broken by neutrino masses (suggested iri connection with late-time phase transitions) is inconsistent with the MSW solution of the solar neutrino problem if it is to account for dark matter. In addition it is shown that a cold dark matter model in which the Compton wavelength of a very light scalar particle accounts for the large-scale structure of the Universe is also ruled out by the effects of pressure on structure formation.
45299887
Can a Brans-Dicke scalar account for dark matter in extended inflation models?
We discuss the possibility that the dark matter in the Universe could be due to the oscillation of the Brans-Dicke scalar in extended inflation models. The constraints following from the requirement that the energy density perturbations due to quantum scalar field fluctuations are within observational limits, and from the requirement that the energy density in the oscillating Brans-Dicke scalar field, induced by the expansion of bubbles at the first-order phase transition, is smaller than the critical density at present, are discussed for the case of a coupling of the Brans-Dicke scalar to the Ricci scalar of the form phi(n+2)/M(n). Solutions of the equations of motion are given in the slow-rolling approximation for a general value of n, and the cases of n = 0 (minimal extended inflation) and n = 2 are discussed in detail. It is shown that the dominant source of energy density fluctuations produced during inflation is the isocurvature fluctuations of the Brans-Dicke scalar. The requirement that the fluctuations in the microwave background due to the isocurvature fluctuations are not too large implies that the reheat temperature at the end of inflation is less than 3 x 10(13) GeV. For the case where gravity is neglected during the expansion of bubbles at the first-order transition and where the isocurvature fluctuations account for the density perturbations observed by COBE, it is shown that only for a very small range of reheat temperatures at the end of inflation is the model consistent with the requirements that the range of non-Newtonian corrections to the gravitational potential is less that 1 cm and that there are no inhomogeneities in the cosmic microwave background radiation due to large bubbles. If we do not require that the isocurvature fluctuations account for the density perturbations observed by COBE, then the range of reheat temperatures can be larger. In general, the range of non-Newtonian corrections to the gravitational potential is not expected to be much smaller than the present upper limits from Cavendish-type experiments. The possible effects of gravitational suppression of the growth of large bubbles is also considered. It is shown that although gravity can suppress the growth of large bubbles, allowing for a wider range of reheat temperatures and shorter range non-Newtonian forces, gravity will have no effect on bubble percolation at the end of the first-order phase transition. The possible advantages of an oscillating Brans-Dicke scalar with respect to structure formation are considered, in particular, the possibility that the Brans-Dicke scalar could account for both cold and hot dark matter in a combined CDM + HDM scenario for structure formation, with the hot component arising from excitation of the Brans-Dicke scalar field by the expansion of bubbles during the first-order phase transition.
14559444
B-ball baryogenesis and the baryon to dark matter ratio
We demonstrate that B-ball decay in the MSSM can naturally solve the puzzle of why the densities of baryons and dark matter in the Universe are similar. This requires that the B-balls survive thermalization and decay below the freeze-out temperature of the neutralino LSP, typically 1-10 GeV, It is shown that this can happen if the baryon asymmetry originates from a squark condensate along the d = 6 u(c)d(c)d(c) D-flat direction of the MSSM scalar potential. For this to work the reheating temperature after inflation must be no greater than 10(3-5) GeV.
119266670
Cosmological evolution of scalar fields and gravitino dark matter in gauge mediation at low reheating temperatures
We consider the dynamics of the supersymmetry-breaking scalar field and the production of dark matter gravitinos via its decay in a gauge-mediated supersymmetry breaking model with metastable vacuum. We find that the scalar field amplitude and gravitino density are extremely sensitive to the parameters of the hidden sector. For the case of an O'Raifeartaigh sector, we show that the observed dark matter density can be explained by gravitinos even for low reheating temperatures TR10GeV. Such low reheating temperatures may be implied by detection of the NLSP at the LHC if its thermal freeze-out density is in conflict with BBN.
16624602
Flat direction dynamics in a non-topological soliton-dominated universe
In running mass inflation and hybrid inflation models it is possible that the inflaton field will fragment into non-topological solitons, resulting in a highly inhomogeneous post-inflation era prior to reheating. In supersymmetric models with a conventional homogeneous post-inflation era, the dynamics of flat direction scalars are determined by cH2 corrections to the mass squared terms (where ), coming from F-terms in the early universe combined with Planck-scale suppressed interactions. Here we reconsider the mass squared corrections for a universe dominated by inflatonic non-topological solitons. We show that in this case the dynamics of a coherently oscillating flat direction scalar are typically the same as for the case where there is no significant mass squared correction, even in the vicinity of the non-topological solitons. Therefore the dynamics of flat direction scalars in a universe dominated by inflatonic non-topological solitons are equivalent to the case c = 0 of a homogeneous universe.
119508847
The dynamics of Affleck-Dine condensate collapse
In the MSSM, cosmological scalar field condensates formed along flat directions of the scalar potential (Affleck-Dine condensates) are typically unstable with respect to formation of Q-balls, a type of non-topological soliton. We consider the dynamical evolution of the Affleck-Dine condensate in the MSSM. We discuss the creation and linear growth, in F- and D-term inflation models, of the quantum seed perturbations which in the non-linear regime catalyse the collapse of the condensate to non-topological soliton lumps. We study numerically the evolution of the collapsing condensate lumps and show that the solitons initially formed are not in general Q-balls, but Q-axitons, a pseudo-breather which can have very different properties from Q-balls of the same charge. We calculate the energy and charge radiated from st spherically symmetric condensate lump as it evolves into a Q-axiton. We also discuss the implications for baryogenesis and dark matter. (C) 2000 Elsevier Science B,V. All rights reserved.
35733734
Parity nonconservation in proton-water scattering at 1.5 GeV/c.
A search has been made for parity nonconservation in the scattering of 1.5-GeV/c (800-MeV) polarized protons from an unpolarized water target. The result for the longitudinal asymmetry is A/sub L/ = (1.7 +- 3.3 +- 1.4) x 10/sup -7/, where the second uncertainty is an estimate of systematic effects. This result is significantly smaller than the value of A/sub L/ for H/sub 2/O reported at 6 GeV/c.
20474546
Measurements of atomic level widths in thulium: Effect on the measurement of neutrino mass from tritium beta decay spectra.
Measurements have been made with curved crystal x-ray spectrometers of the natural line widths of the L/sub 1/M/sub 2/ (GAMMA = 12.1 +- 2 eV), L/sub 1/M/sub 3/ (GAMMA = 12.7 +- 1 eV), and M/sub 1/N/sub 3/ (GAMMA = 19 +- 3 eV) atomic transitions in Tm. These results are combined with published results to determine M/sub 1/, M/sub 2/, and M/sub 3/ internal conversion line widths for /sup 169/Tm. These lines have been used in the calibration of a beta spectrometer for recent measurements of the electron antineutrino mass from the tritium beta decay spectrum. A reanalysis of these results suggests that there is no conclusive evidence for a finite mass for the electron antineutrino.
22445170
Polarized, high-density, gaseous 3He targets.
28969238
Total width of the 5.17 MeV 1(-) state in 14O and the hot-CNO cycle.
46704072
Restrictions on a 1.7-MeV axion from nuclear pair transitions.
We analyze nuclear internal-pair-transition experiments for evidence of a possible 1.7-MeV axion and find that the conventional axion and the new axions described by the theories of Krauss and Wilczek and of Peccei, Wu, and Yanagida are inconsistent with these data. The results are independent of nuclear models.