arXiv subjects

Valerie Domcke

Publications and source records attributed to Valerie Domcke.

80 records · Page 5Linked to original sources

arXiv2014

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.

hep-th↗

arXiv2014

GUT-scale inflation with sizeable tensor modes

A sizeable tensor-to-scalar ratio, such as recently claimed by BICEP2, would imply a scale of inflation at the typical scale of supersymmetric grand unification. This could be an accident, or strong support for supersymmetric theories. Models of F-term hybrid inflation naturally connect the GUT scale with the inflationary scale, but they also predict the tensor-to-scalar ratio to be unmeasurably small. In this work we analyze a general UV embedding of F-term hybrid inflation into a supergravity theory with a general Kahler potential. The CMB observables are generated during the early phase of inflation, at large inflaton values, where the potential is dominated by Planck-suppressed operators. Tuning the leading higher-order terms can give an inflaton potential with sizeable tensor fluctuations and a field excursion which is still sub-Planckian but close to the Planck scale, as expected from the Lyth bound.

hep-ph↗

arXiv2014

Hybrid Inflation in the Complex Plane

Supersymmetric hybrid inflation is an exquisite framework to connect inflationary cosmology to particle physics at the scale of grand unification. Ending in a phase transition associated with spontaneous symmetry breaking, it can naturally explain the generation of entropy, matter and dark matter. Coupling F-term hybrid inflation to soft supersymmetry breaking distorts the rotational invariance in the complex inflaton plane---an important fact, which has been neglected in all previous studies. Based on the delta-N formalism, we analyze the cosmological perturbations for the first time in the full two-field model, also taking into account the fast-roll dynamics at and after the end of inflation. As a consequence of the two-field nature of hybrid inflation, the predictions for the primordial fluctuations depend not only on the parameters of the Lagrangian, but are eventually fixed by the choice of the inflationary trajectory. Recognizing hybrid inflation as a two-field model resolves two shortcomings often times attributed to it: The fine-tuning problem of the initial conditions is greatly relaxed and a spectral index in accordance with the PLANCK data can be achieved in a large part of the parameter space without the aid of supergravity corrections. Our analysis can be easily generalized to other (including large-field) scenarios of inflation in which soft supersymmetry breaking transforms an initially single-field model into a multi-field model.

hep-ph↗

arXiv2014

No-scale D-term inflation with stabilized moduli

We study the consistency of hybrid inflation and moduli stabilization, using the Kallosh--Linde model as an example for the latter. We find that F-term hybrid inflation is not viable since inflationary trajectories are destabilized by tachyonic modes. On the other hand, D-term hybrid inflation is naturally compatible with moduli stabilization due to the absence of a large superpotential term during the inflationary phase. Our model turns out to be equivalent to superconformal D-term inflation and it therefore successfully accounts for the CMB data in the large-field regime. Supersymmetry breaking can be incorporated via an O'Raifeartaigh model. For GUT-scale inflation one obtains stringent bounds on the gravitino mass. A rough estimate yields 10^5 GeV \lesssim m_3/2 \lesssim 10^10 GeV, contrary to naive expectation.

hep-th↗

arXiv2013

The Gravitational Wave Spectrum from Cosmological B-L Breaking

Cosmological B-L breaking is a natural and testable mechanism to generate the initial conditions of the hot early universe. If B-L is broken at the grand unification scale, the false vacuum phase drives hybrid inflation, ending in tachyonic preheating. The decays of heavy B-L Higgs bosons and heavy neutrinos generate entropy, baryon asymmetry and dark matter and also control the reheating temperature. The different phases in the transition from inflation to the radiation dominated phase produce a characteristic spectrum of gravitational waves. We calculate the complete gravitational wave spectrum due to inflation, preheating and cosmic strings, which turns out to have several features. The production of gravitational waves from cosmic strings has large uncertainties, with lower and upper bounds provided by Abelian Higgs strings and Nambu-Goto strings, implying Ω_GW h^2 ~ 10^{-13} - 10^{-8}, much larger than the spectral amplitude predicted by inflation. Forthcoming gravitational wave detectors such as eLISA, advanced LIGO, ET, and BBO/DECIGO will reach the sensitivity needed to test the predictions from cosmological B-L breaking.

hep-ph↗

arXiv2012

WIMP Dark Matter from Gravitino Decays and Leptogenesis

The spontaneous breaking of B-L symmetry naturally accounts for the small observed neutrino masses via the seesaw mechanism. We have recently shown that the cosmological realization of B-L breaking in a supersymmetric theory can successfully generate the initial conditions of the hot early universe, i.e. entropy, baryon asymmetry and dark matter, if the gravitino is the lightest superparticle (LSP). This implies relations between neutrino and superparticle masses. Here we extend our analysis to the case of very heavy gravitinos which are motivated by hints for the Higgs boson at the LHC. We find that the nonthermal production of 'pure' wino or higgsino LSPs, i.e. weakly interacting massive particles (WIMPs), in heavy gravitino decays can account for the observed amount of dark matter while simultaneously fulfilling the constraints imposed by primordial nucleosynthesis and leptogenesis within a range of LSP, gravitino and neutrino masses. For instance, a mass of the lightest neutrino of 0.05 eV would require a higgsino mass below 900 GeV and a gravitino mass of at least 10 TeV.

hep-ph↗

arXiv2012

Spontaneous B-L Breaking as the Origin of the Hot Early Universe

The decay of a false vacuum of unbroken B-L symmetry is an intriguing and testable mechanism to generate the initial conditions of the hot early universe. If B-L is broken at the grand unification scale, the false vacuum phase yields hybrid inflation, ending in tachyonic preheating. The dynamics of the B-L breaking Higgs field and thermal processes produce an abundance of heavy neutrinos whose decays generate entropy, baryon asymmetry and gravitino dark matter. We study the phase transition for the full supersymmetric Abelian Higgs model. For the subsequent reheating process we give a detailed time-resolved description of all particle abundances. The competition of cosmic expansion and entropy production leads to an intermediate period of constant 'reheating' temperature, during which baryon asymmetry and dark matter are produced. Consistency of hybrid inflation, leptogenesis and gravitino dark matter implies relations between neutrino parameters and superparticle masses. In particular, for a gluino mass of 1 TeV, we find a lower bound on the gravitino mass of 10 GeV.

hep-ph↗

arXiv2012

Predicting theta_13 and the Neutrino Mass Scale from Quark Lepton Mass Hierarchies

Flavour symmetries of Froggatt-Nielsen type can naturally reconcile the large quark and charged lepton mass hierarchies and the small quark mixing angles with the observed small neutrino mass hierarchies and their large mixing angles. We point out that such a flavour structure, together with the measured neutrino mass squared differences and mixing angles, strongly constrains yet undetermined parameters of the neutrino sector. Treating unknown O(1) parameters as random variables, we obtain surprisingly accurate predictions for the smallest mixing angle, sin^2(2 theta_13) = 0.07 (+0.11)(-0.05), the smallest neutrino mass, m_1 = 2.2 (+1.7)(-1.4) x 10^-3 eV, and one Majorana phase, alpha_21 / pi = 1.0 (+0.2)(-0.2).

hep-ph↗