259 research outputs found
Saddle point inflation from higher order corrections to Higgs/Starobinsky inflation
We explore two saddle point inflationary scenarios in the context of higher
order corrections related to different generalisations of general relativity.
Firstly, we deal with Jordan frame Starobinsky potential, for which we identify
a portion of a parameter space of inflection point inflation, which can
accommodate all the experimental results. Secondly, we analyse Higgs inflation
and more specifically the influence of non-renormalisible terms on the standard
quartic potential. All results were verified with the PLANCK 2015 data.Comment: 17 pages, 6 figure
Saddle point inflation from theory
We analyse several saddle point inflationary scenarios based on power-law
models. We investigate inflation resulting from and as well as limit of the latter. In all cases we
have found relation between coefficients and checked consistency
with the PLANCK data as well as constraints coming from the stability of the
models in question. Each of the models provides solutions which are both stable
and consistent with PLANCK data, however only in parts of the parameter space
where inflation starts on the plateau of the potential, some distance from the
saddle. And thus all the correct solutions bear some resemblance to the
Starobinsky model.Comment: 10 pages, 8 figure
Higher-order scalar interactions and SM vacuum stability
Investigation of the structure of the Standard Model effective potential at
very large field strengths opens a window towards new phenomena and can reveal
properties of the UV completion of the SM. The map of the lifetimes of the
vacua of the SM enhanced by nonrenormalizable scalar couplings has been
compiled to show how new interactions modify stability of the electroweak
vacuum. Whereas it is possible to stabilize the SM by adding Planck scale
suppressed interactions and taking into account running of the new couplings,
the generic effect is shortening the lifetime and hence further destabilisation
of the SM electroweak vacuum. These findings have been illustrated with phase
diagrams of modified SM-like models. It has been demonstrated that
stabilisation can be achieved by lowering the suppression scale of higher order
operators while picking up such combinations of new couplings, which do not
deepen the new minima of the potential. Our results show the dependence of the
lifetime of the electroweak minimum on the magnitude of the new couplings,
including cases with very small couplings (which means very large effective
suppression scale) and couplings vastly different in magnitude (which
corresponds to two different suppression scales).Comment: plain Latex, 9 figure
Implications of extreme flatness in a general f(R) theory
We discuss a modified gravity theory defined by . We consider both finite and infinite number of terms in the
series while requiring that the Einstein frame potential of the theory has a
flat area around any of its stationary points. We show that the requirement of
maximally flat stationary point leads to the existence of the saddle point
(local maximum) for even (odd) . In both cases for one obtains
the Starobinsky model with small, exponentially suppressed corrections. Besides
the GR minimum the Einstein frame potential has an anti de Sitter vacuum.
However we argue that the GR vacuum is absolutely stable and AdS cannot be
reached neither via classical evolution nor via quantum tunnelling. Our results
show that a Starobinsky-like model is the only possible realisation of
theory with an extremely flat area in the Einstein frame potential.Comment: 13 pages, 4 figure
Inflationary scenarios in Starobinsky model with higher order corrections
We consider the Starobinsky inflation with a set of higher order corrections
parametrised by two real coefficients . In the Einstein
frame we have found a potential with the Starobinsky plateau, steep slope and
possibly with an additional minimum, local maximum or a saddle point. We have
identified three types of inflationary behaviour that may be generated in this
model: i) inflation on the plateau, ii) at the local maximum (topological
inflation), iii) at the saddle point. We have found limits on parameters
and initial conditions at the Planck scale which enable successful
inflation and disable eternal inflation at the plateau. We have checked that
the local minimum away from the GR vacuum is stable and that the field cannot
leave it neither via quantum tunnelling nor via thermal corrections.Comment: 20 pages, 9 figure
Upper bounds on sparticle masses from muon g-2 and the Higgs mass and the complementarity of future colliders
Supersymmetric (SUSY) explanation of the discrepancy between the measurement
of and its SM prediction puts strong upper bounds on the chargino
and smuon masses. At the same time, lower experimental limits on the chargino
and smuon masses, combined with the Higgs mass measurement, lead to an upper
bound on the stop masses. The current LHC limits on the chargino and smuon
masses (for not too compressed spectrum) set the upper bound on the stop masses
of about 10 TeV. The discovery potential of the future lepton and hadron
colliders should lead to the discovery of SUSY if it is responsible for the
explanation of the anomaly. This conclusion follows from the fact
that the upper bound on the stop masses decreases with the increase of the
lower experimental limit on the chargino and smuon masses.Comment: 14 pages, 4 figures; v2: fig.2, comments and references added,
matches published versio
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