119540567
Dark Energy Cosmology with Spinor Field
Recent observations have shown that our universe is currently undergoing a period of accelerating expansion. In view of the astrophysical data we find that the equation of state of the dark energy lies in a narrow range around w = −1. In this paper we discuss the possibility of treating a spinor field as dark energy to realize the equation of state parameter w < −1 or w > −1. We derive the main equations which govern the evolution of the universe and then discuss the evolution and attractor property of this model, and show a late time de Sitter attractor. Finally we rewrite them with the observable quantities.
120629236
Dark Energy Cosmology with a Rarita-Schwinger Field
Recent observations of the Cosmic Microwave Background, Supernovae and Sloan Digital Sky Survey (SDSS) show that our universe has a critical energy density, and roughly 2/3 of it is dark energy, which drives the accelerating expansion of the cosmos. In view of the astrophysical data, we find that the equation of state parameter of the dark energy lies in a narrow range around w = −1. In this paper, we construct a cosmology model with a Rarita-Schwinger field to realize the equation of state parameter w < −1 or w > −1 and discuss its stability.
123261615
Holographic Dark Energy in Induced Gravity
Many astrophysics data show that our universe has a critical energy density, and 73% of it is dark energy, which drives the accelerating expansion of the universe. We consider the holographic dark energy in induced gravity by taking the Hubble scale, particle horizon and event horizon as the infrared cutoff. We find that only the event horizon can give accelerating expansion of our universe.
17747890
Phantom cosmology with non-minimally coupled real scalar field
We find that the expansion of the universe is accelerating by analyzing the recent observation data of type Ia supernova (SN-Ia). It indicates that the equation of state of the dark energy might be smaller than -1, which leads to the introduction of phantom models featured by its negative kinetic energy to account for the regime of equation of state parameter w < -1. In this paper the possibility of using a non-minimally coupled real scalar field as phantom to realize the equation of state parameter w < -1 is discussed. The main equations which govern the evolution of the universe are obtained. Then we rewrite them with the observable quantities.
119022393
R symmetries in the landscape
In the landscape, states with R symmetries at the classical level form a distinct branch, with a potentially interesting phenomenology. Some preliminary analyses suggested that the population of these states would be significantly suppressed. We survey orientifolds of IIB theories compactified on Calabi-Yau spaces based on vanishing polynomials in weighted projective spaces, and find that the suppression is quite substantial. On the other hand, we find that a Z2 R-parity is a common feature in the landscape. We discuss whether the cosmological constant and proton decay or cosmology might select the low energy branch. We include also some remarks on split supersymmetry.
119110201
Vacuum statistics and parameter tuning for F-term supersymmetry breaking
We carry out a model-independent EFT method study on the vacuum statistics of general F-term SUSY breaking models. Assuming a smooth distribution of Lagrangian parameters, SUSY breaking vacua are rare in global SUSY models with a canonical Kähler potential, and have a peaked distribution near the cut-off of the SUSY breaking scale in both global SUSY and SUGRA models with a general Kähler potential. After including different mass scales in the Lagrangian, we compare the total number of SUSY and non-SUSY vacua and estimate quantitatively the rareness of SUSY breaking. The EFT method provides a general view to the amount of parameter tuning needed for a metastable SUSY breaking vacuum. The tuning also indicates the importance of R-symmetries in SUSY breaking even for metastable SUSY breaking.
119281514
The Nelson-Seiberg theorem revised
A bstractThe well-accepted Nelson-Seiberg theorem relates R-symmetries to supersymmetry (SUSY) breaking vacua, and provides a guideline for SUSY model building which is the most promising physics beyond the Standard Model. In the case of Wess-Zumino models with perturbative superpotentials, we revise the theorem to a combined necessary and sufficient condition for SUSY breaking which can be easily checked before solving the vacuum. The revised theorem provides a powerful tool to construct either SUSY breaking or SUSY vacua, and offers many practicable applications in low energy SUSY model building and string phenomenology.
119163417
Low energy supersymmetry from R-symmetries
Abstract In a generic setting of Wess–Zumino models, we prove that the existence of a supersymmetric vacuum with a vanishing superpotential can be a consequence of a continuous or discrete R-symmetry when invariant fields are not less than fields transforming in the same way as the superpotential under the R-symmetry. The realization in string theory is discussed. We show that a rich landscape of low energy supersymmetric vacua can be found in the Type IIB flux compactification setup ready for the KKLT construction of de Sitter vacua in string theory.
123570279
Investigation of two-proton emission from excited states of the odd-Z nucleus P-28 by complete-kinematics measurements
An experiment to study exotic two-proton emission from excited levels of the odd-Z nucleus {sup 28}P was performed at the National Laboratory of Heavy Ion Research-Radioactive Ion Beam Line (HIRFL-RIBLL) facility. The projectile {sup 28}P at the energy of 46.5 MeV/u was bombarding a {sup 197}Au target to populate the excited states via Coulomb excitation. Complete-kinematics measurements were realized by the array of silicon strip detectors and the CsI+PIN telescope. Two-proton events were selected and the relativistic-kinematics reconstruction was carried out. The spectrum of relative momentum and opening angle between two protons was deduced from Monte Carlo simulations. Experimental results show that two-proton emission from {sup 28}P excited states less than 17.0 MeV is mainly two-body sequential emission or three-body simultaneous decay in phase space. The present simulations cannot distinguish these two decay modes. No obvious diproton emission was found.