42466564
CP violation for electroweak baryogenesis from mixing of standard model and heavy vector quarks.
It is known that the CP violation in the minimal standard model is insufficient to explain the observed baryon asymmetry of the Universe in the context of electroweak baryogenesis. In this paper we consider the possibility that the additional CP violation required could originate in the mixing of the standard model quarks and heavy vector quark pairs. We consider the baryon asymmetry in the context of the spontaneous baryogenesis scenario. It is shown that, in general, the CP-violating phase entering the mass matrix of the standard model and heavy vector quarks must be space dependent in order to produce a baryon asymmetry, suggesting that the additional CP violation must be spontaneous in nature. This is true for the case of the simplest models which mix the standard model and heavy vector quarks. We derive a charge potential term for the model by diagonalizing the quark mass matrix in the presence of the electroweak bubble wall, which turns out to be quite different from the fermionic hypercharge potentials usually considered in spontaneous baryogenesis models, and obtain the rate of baryon number generation within the wall. We find, for the particular example where the standard model quarks mix with weak-isodoublet heavy vector quarks via the expectation value of a gauge singlet scalar, that we, can account for the observed baryon asymmetry with conservative estimates for the uncertain parameters of electroweak baryogenesis, provided that the heavy vector quarks are not heavier than a few hundred GeV and that the coupling of the standard model quarks to the heavy vector quarks and gauge singlet scalars is not much smaller than order of 1, corresponding to a mixing angle of the heavy vector quarks and standard model quarks not much smaller than order of 10(-1).
14318680
Supergravity and two-field inflation effects in right-handed sneutrino modified D-term inflation.
We extend previous work on the minimal D-term inflation model modified by right-handed (RH) sneutrino fields to include additional inflaton-sector supergravity corrections and two-field inflation effects. We show that supergravity corrections simultaneously allow ns to be within 3-year Wilkinson Microwave Anisotropy Probe limits and the cosmic string contribution to the cosmic microwave background (CMB) power spectrum to be less than 5%. For gauge coupling g 0.1H. The running spectral index is alpha[approximate]-0.0002 when mPhi 0.008 for mPhi>1.0H.
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.
14078444
Dynamical cosmological constant from a very recent phase transition
Observation indicates that the expansion of the Universe is accelerating and favours a dynamical cosmological constant, Λ(t). We consider the possibility that this is due to a scalar field which has undergone a very recent phase transition. We study a simple class of model, corresponding to a φ4 potential with a time-dependent mass squared term. For the models considered the phase transition occurs at a red shift z⩽1.2. The evolution of the equation of state ωφ and energy density ρφ with time is distinct from existing dynamical Λ models based on slowly rolling fields, with ωφ and ρφ rapidly changing in a characteristic way following the transition. The φ energy density is composed of a time-dependent vacuum energy and coherently oscillating condensate component with a negative pressure. The condensate component will typically collapse to form non-topological soliton lumps, ‘φ-axitons’, which smoothly populate the Universe.
2260171
SUPERSYMMETRIC D-TERM INFLATION AND B-BALL BARYOGENESIS
We consider the B-ball cosmology of the minimal supersymmetric standard model in the context of D-term inflation models where the reheating temperature is determined by the Affleck-Dine mechanism to be of the order of 1 GeV. We show that such a low reheating temperature can arise quite naturally as the result of a symmetry which is required to maintain the flatness of the inflaton potential. In this case the B-balls will decay well after the freeze-out temperature of the lightest supersymmetric particle, allowing baryons and cold dark matter to originate primarily from B-ball decays. [S0031-9007(98)07324-4].
15615901
Reheating temperature and inflaton mass bounds from thermalization after inflation
We consider the conditions for the decay products of perturbative inflaton decay to thermalize. The importance of considering the full spectrum of inflaton decay products in the thermalization process is emphasized. For the case of single field inflation models, it is shown that the delay between the end of inflaton decay and thermalization allows the thermal gravitino upper bound on the reheating temperature to be raised from 10(8) GeV to as much as 10(12) GeV in realistic inflation models. Requiring that thermalization occurs before nucleosynthesis imposes an upper bound on the inflaton mass as a function of the reheating temperature, m(S) less than or similar to 10(10)(T-R/1 GeV)(7/9) GeV. It is also shown that even in realistic inflation models with relatively large reheating temperatures, it is non-trivial to have thermalization before the electroweak phase transition temperature. Therefore the thermal history of the Universe is very sensitive to details of the inflation model.
26401416
Weak pion-nucleon coupling strength: New constraint from parity mixing in 18F.
The circular polarization of the 1.081 MeV γ rays from 18F has been measured to be (1.7±5.8)×10-4. 18F was produced by a 4.05 MeV 3He+ beam impinging on a recirculating water target with a thin entrance window. The circular polarization was measured with four magnetic transmission polarimeters, each backed by a 150 cm3 n-type Ge detector. A fast data acquisition system limited overall peak losses to 30% at a count rate of 60 kHz per detector. Supplementary experiments were carried out to investigate the sensitivity of the circular polarization measurement to systematic variations of beam position and intensity. These effects were found to be negligible relative to the statistical uncertainty. The experimental result is interpreted in terms of an isovector parity-nonconserving matrix element between the ‖0+,T=1,1.042 MeV〉 and ‖0-,T=0,1.081 MeV〉 states in 18F that is dominated by the weak pion exchange contribution. The present result for the weak pion-nucleon coupling strength is ‖fπ1‖=(0.4-0.4+1.4)×10-7, which is significantly smaller than recent theoretical predictions based on the Weinberg-Salam model.
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.