2,338,032 research outputs found

### Long Term Mitigation Scenarios: Strategic Options for South Africa

The focus of this document is mitigation: if South Africa takes the decision to mitigate, then this document addresses how to determine the options, the emissions reductions achieved by these options, and the attendant costs of each option. How, then, is South Africa to grow and develop in order to reduce poverty, while at the same time retooling its economy in order to reduce its greenhouse gas emissions

### Deflationary Universe Scenario

We show that it is possible to realize an inflationary scenario even without
conversion of the false vacuum energy to radiation. Such cosmological models
have a deflationary stage in which $Ha^2$ is decreasing and radiation produced
by particle creation in an expanding Universe becomes dominant. The preceding
inflationary stage ends since the inflaton potential becomes steep. False
vacuum energy is finally (partly) converted to the inflaton kinetic energy ,
the potential energy rapidly decreases and the Universe comes to the
deflationary stage with a scale factor $a(t) \propto t^{1/3}$. Basic features
and observational consequences of this scenario are indicated.Comment: 18p, KUNS-1201 Plain TeX, phyzzx. Reference file is included which
previously was misse

### Gribov's Confinement Scenario

I give a brief account of Gribov's scenario of supercritical charges in QCD.
Gribov's equation for the Green function of light quarks and its derivation
from the corresponding Dyson-Schwinger equation are described. The resulting
Green function is shown to exhibit chiral symmetry breaking.Comment: 4 pages, 1 figure, Talk presented at the Xth International Light-Cone
Meeting on Non-Perturbative QCD and Hadron Phenomenology, Heidelberg, June
200

### Curvature Inspired Cosmological Scenario

Using modified gravity with non-linear terms of curvature, $R^2$ and $R^{(r
+2)}$ (with $r$ being the positive real number and $R$ being the scalar
curvature), cosmological scenario,beginning at the Planck scale, is obtained.
Here, a unified picture of cosmology is obtained from $f(R)-$ gravity. In this
scenario, universe begins with power-law inflation, followed by deceleration
and acceleration in the late universe as well as possible collapse of the
universe in future. It is different from $f(R)-$ dark energy models with
non-linear curvature terms assumed as dark energy. Here, dark energy terms are
induced by linear as well as non-linear terms of curvature in Friedmann
equation being derived from modified gravity.It is also interesting to see
that, in this model, dark radiation and dark matter terms emerge spontaneously
from the gravitational sector. It is found that dark energy, obtained here,
behaves as quintessence in the early universe and phantom in the late universe.
Moreover, analogous to brane-tension in brane-gravity inspired Friedmann
equation, a tension term $\lambda$ arises here being called as cosmic tension.
It is found that, in the late universe, Friedmann equation (obtained here)
contains a term $- \rho^2/2\lambda$ ($\rho$ being the phantom energy density)
analogous to a similar term in Friedmann equation with loop quantum effects, if
$\lambda > 0$ and brane-gravity correction when $\lambda < 0.$Comment: 19 Pages. To appear in Int. J. Thro. Phy

### The degenerate gravitino scenario

In this work, we explore the "degenerate gravitino" scenario where the mass
difference between the gravitino and the lightest MSSM particle is much smaller
than the gravitino mass itself. In this case, the energy released in the decay
of the next to lightest sypersymmetric particle (NLSP) is reduced. Consequently
the cosmological and astrophysical constraints on the gravitino abundance, and
hence on the reheating temperature, become softer than in the usual case. On
the other hand, such small mass splittings generically imply a much longer
lifetime for the NLSP. We find that, in the constrained MSSM (CMSSM), for
neutralino LSP or NLSP, reheating temperatures compatible with thermal
leptogenesis are reached for small splittings of order 10^{-2} GeV. While for
stau NLSP, temperatures of 4x10^9 GeV can be obtained even for splittings of
order of tens of GeVs. This "degenerate gravitino" scenario offers a possible
way out to the gravitino problem for thermal leptogenesis in supersymmetric
theories.Comment: 27 pages, 10 figures and 1 table. Minor typos and references fixed.
Matches published version in JCAP

### A Minimal Inflation Scenario

We elaborate on a minimal inflation scenario based entirely on the general
properties of supersymmetry breaking in supergravity models. We identify the
inflaton as the scalar component of the Goldstino superfield. We write
plausible candidates for the effective action describing this chiral
superfield. In particular the theory depends (apart from parameters of O(1)) on
a single free parameter: the scale of supersymmetry breaking. This can be fixed
using the amplitude of CMB cosmological perturbations and we therefore obtain
the scale of supersymmetry breaking to be 10^{12-14} GeV. The model also
incorporates explicit R-symmetry breaking in order to satisfy the slow roll
conditions. In our model the eta-problem is solved without extra fine-tuning.
We try to obtain as much information as possible in a model independent way
using general symmetry properties of the theory's effective action, this leads
to a new proposal on how to exit the inflationary phase and reheat the
Universe.Comment: matches published version (typo corrected

- âŠ