1,153 research outputs found
Inflation from High-Scale Supersymmetry Breaking
Supersymmetry breaking close to the scale of grand unification can explain
cosmic inflation. As we demonstrate in this paper, this can be achieved in
strongly coupled supersymmetric gauge theories, such that the energy scales of
inflation and supersymmetry breaking are generated dynamically. As a
consequence, both scales are related to each other and exponentially suppressed
compared to the Planck scale. As an example, we consider a dynamical model in
which gauging a global flavor symmetry in the supersymmetry-breaking sector
gives rise to a Fayet-Iliopoulos D term. This results in successful D-term
hybrid inflation in agreement with all theoretical and phenomenological
constraints. The gauged flavor symmetry can be identified with U(1)_B-L, where
B and L denote baryon and lepton number, respectively. In the end, we arrive at
a consistent cosmological scenario that provides a unified picture of
high-scale supersymmetry breaking, viable D-term hybrid inflation, spontaneous
B-L breaking at the scale of grand unification, baryogenesis via leptogenesis,
and standard model neutrino masses due to the type-I seesaw mechanism.Comment: 61 pages + references, 5 figures. v2: minor changes, updated
references, matches version published in PR
Charge transport through a flexible molecular junction
Vibrationally inelastic electron transport through a flexible molecular
junction is investigated. The study is based on a mechanistic model for a
biphenyl molecule between two metal electrodes. Employing methods from
electron-molecule scattering theory, which allow a numerically exact treatment,
we study the effect of vibrational excitation on the transmission probability
for different parameter regimes. The current-voltage characteristic is analyzed
for different temperatures, based on a Landauer-type formula. Furthermore, the
process of electron assisted tunneling between adjacent wells in the torsional
potential of the molecule is discussed and the validity of approximate methods
to describe the transmission probability is investigated.Comment: 14 pages, Submited to Czech. J. Phy
The Chaotic Regime of D-Term Inflation
We consider D-term inflation for small couplings of the inflaton to matter
fields. Standard hybrid inflation then ends at a critical value of the inflaton
field that exceeds the Planck mass. During the subsequent waterfall transition
the inflaton continues its slow-roll motion, whereas the waterfall field
rapidly grows by quantum fluctuations. Beyond the decoherence time, the
waterfall field becomes classical and approaches a time-dependent minimum,
which is determined by the value of the inflaton field and the self-interaction
of the waterfall field. During the final stage of inflation, the effective
inflaton potential is essentially quadratic, which leads to the standard
predictions of chaotic inflation. The model illustrates how the decay of a
false vacuum of GUT-scale energy density can end in a period of `chaotic
inflation'.Comment: 15 pages, 6 figures. v3: matches version published in JCA
Dynamical D-Terms in Supergravity
Most phenomenological models of supersymmetry breaking rely on nonzero
F-terms rather than nonzero D-terms. An important reason why D-terms are often
neglected is that it turns out to be very challenging to realize D-terms at
energies parametrically smaller than the Planck scale in supergravity. As we
demonstrate in this paper, all conventional difficulties may, however, be
overcome if the generation of the D-term is based on strong dynamics. To
illustrate our idea, we focus on a certain class of vector-like SUSY breaking
models that enjoy a minimal particle content and which may be easily embedded
into more complete scenarios. We are then able to show that, upon gauging a
global flavor symmetry, an appropriate choice of Yukawa couplings readily
allows to dynamically generate a D-term at an almost arbitrary energy scale.
This includes in particular the natural and consistent realization of D-terms
around, above and below the scale of grand unification in supergravity, without
the need for fine-tuning of any model parameters. Our construction might
therefore bear the potential to open up a new direction for model building in
supersymmetry and early universe cosmology.Comment: 34 pages, 1 tabl
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