arXiv subjects

Rachel Jeannerot

Publications and source records attributed to Rachel Jeannerot.

15 recordsLinked to original sources

arXiv2008

Racetrack Inflation and Cosmic Strings

We consider the coupling of racetrack inflation to matter fields as realised in the D3/D7 brane system. In particular, we investigate the possibility of cosmic string formation in this system. We find that string formation before or at the onset of racetrack inflation is possible, but they are then inflated away. Furthermore, string formation at the end of inflation is prevented by the presence of the moduli sector. As a consequence, no strings survive racetrack inflation.

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arXiv2007

D-term Uplifted Racetrack Inflation

It is shown that racetrack inflation can be implemented in a moduli stabilisation scenario with a supersymmetric uplifting D-term. The resulting model is completely described by an effective supergravity theory, in contrast to the original racetrack models. We study the inflationary dynamics and show that the gaugino condensates vary during inflation. The resulting spectral index is n_s = 0.95 as in the original racetrack inflation model. Hence extra fields do not appear to alter the predictions of the model. An equivalent, simplified model with just a single field is presented.

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arXiv2007

Warping and F-term uplifting

We analyse the effective supergravity model of a warped compactification with matter on D3 and D7-branes. We find that the main effect of the warp factor is to modify the F-terms while leaving the D-terms invariant. Hence warped models with moduli stabilisation and a small positive cosmological constant resulting from a large warping can only be achieved with an almost vanishing D-term and a F-term uplifting. By studying string-motivated examples with gaugino condensation on magnetised D7-branes, we find that even with a vanishing D-term, it is difficult to achieve a Minkowski minimum for reasonable parameter choices. When coupled to an ISS sector the AdS vacua is uplifted, resulting in a small gravitino mass for a warp factor of order 10^-5.

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arXiv2007

D-term inflation after spontaneous symmetry breaking

We show that 1-loop quantum corrections to the potential energy density in supersymmetric hybrid inflation, outside the inflationary valley, can not be neglected. A method is presented to calculate these 1-loop corrections and they are applied to the case of D-term hybrid inflation, where a significant amount of inflation is shown to occur after spontaneous symmetry breaking. Taking this into account improves the agreement with WMAP measurements. A gauge coupling of up to 0.3 is still consistent with the CMB density perturbation. The spectral index is predicted in between 0.98 and 1.00 and the cosmic string contribution to the CMB anisotropy is sufficiently reduced.

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arXiv2006

Enlarging the parameter space of standard hybrid inflation

We show that the parameter space for F-term inflation which predict the formation of cosmic strings is larger than previously estimated. Firstly, because realistic embeddings in GUT theories alter the standard scenerio, making the inflationary potential less steep. Secondly, the strings which form at the end of inflation are not necessarily topologically stable down to low scales. In shifted and smooth inflation strings do not form at all. We also discuss D-term inflation; here the possibilities are much more limited to enlargen paramer space.

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arXiv2006

Inflation, Strings, CMB anisotropies and Leptogenesis

In this talk, I shall focus on theories beyond the Standard Model which predict massive neutrinos. Hybrid inflation emerges naturally in these theories: the slow-rolling inflaton field is a gauge singlet which couples with a GUT Higgs field which triggers the end of inflation. In the standard scenario, spontaneous symmetry breaking takes place at the end of inflation at a scale $M$; $M_{GUT} > M > M_Z$ for inflation to solve the GUT monopole problem and cosmic strings always form at this intermediate scale. WMAP data constrain $M \in [10^{14.5}-10^{15.5}]$ GeV and the singlet-Higgs coupling $κ\in [10^{-7} - 10^{-2}]$. The spectral index $n_s \gtrsim 0.98$ in slight conflict with WMAP3. When the symmetry which is broken at the end of inflation is gauged $B-L$, both the inflaton and the strings decay into right-handed neutrinos. There are then two competing non-thermal scenarios for baryogenesis via leptogenesis which take place at the end of inflation, during reheating and from cosmic strings decay. Which of the two scenarios dominates depends on the inflaton-neutrino sector parameters.

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arXiv2006

GUT cosmic strings and inflation

We show that GUT cosmic strings generically form after inflation if a {\it non-inert} symmetry breaks after inflation; they form irrespectively of the inflationary scenario and in both supersymmetric and non-supersymmetric theories.

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arXiv2006

Grand unified models and cosmology

The cosmological consequences of particle physics grand unified theories (GUTs) are studied. Cosmological models are implemented in realistic particle physics models. Models consistent from both particle physics and cosmological considerations are selected. (...)

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arXiv2005

Leptogenesis from reheating after inflation and cosmic string decay

Cosmic strings form at the end of standard supersymmetric hybrid inflation, and both inflation and strings contribute to the CMB anisotropies. If the symmetry which is broken at the end of inflation is gauged $B$-$L$, there is a mixed scenario for leptogenesis: Right-handed neutrinos can be produced non-thermally during reheating via inflaton decay as well as via cosmic string decay. We show that the parameter space consistent with CMB data can accommodate either or both scenarios depending on the mass of the right-handed neutrinos.

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arXiv2005

Confronting hybrid inflation in supergravity with CMB data

$F$-term GUT inflation coupled to N=1 Supergravity is confronted with CMB data. Corrections to the string mass-per-unit-length away from the Bogomolny limit are taken into account. We find that a superpotential coupling $10^{-7}/\mcN \lesssim κ\lesssim 10^{-2}/\mcN$, with $\mcN$ the dimension of the Higgs-representation, is still compatible with the data. The parameter space is enlarged in warm inflation, as well as in the curvaton and inhomogeneous reheat scenario. $F$-strings formed at the end of $P$-term inflation are also considered. Because these strings satisfy the Bogomolny bound the bounds are stronger: the gauge coupling is constrained to the range $10^{-7} < g <10^{-4}$.

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arXiv2005

Majorana zero modes

We derive the zero mode solutions for a Majorana fermion in the background of a cosmic string and contrast it with the zero mode solution for a (neutral) Dirac fermion. A Majorana zero mode carries no vector or axial charge, and it cannot be bosonised. We study the implications for vorton formation and stability. In the massless limit stability of the zero mode is guaranteed by energy-momentum conservation. However, zero modes obtain an effective mass on string loops. It is found that the conditions under which current formation can be effective are exactly those for which zero mode decay is most likely to occur.

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arXiv2005

Chiral cosmic strings in supergravity

We consider F and D-term cosmic strings formed in supersymmetric theories. Supersymmetry is broken inside the string core, but restored outside. In global SUSY, this implies the existence of goldstino zero modes, and the string potentially carries fermionic currents. We show that these zero modes do not survive the coupling to gravity, due to the super Higgs mechanism. Therefore the superconductivity and chirality properties are different in global and local supersymmetry. For example, a string formed at the end of D-term inflation is chiral in supergravity but non-chiral in global SUSY.

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arXiv2003

How generic is cosmic string formation in SUSY GUTs

We study cosmic string formation within supersymmetric grand unified theories. We consider gauge groups having a rank between 4 and 8. We examine all possible spontaneous symmetry breaking patterns from the GUT down to the standard model gauge group. Assuming standard hybrid inflation, we select all the models which can solve the GUT monopole problem, lead to baryogenesis after inflation and are consistent with proton lifetime measurements. We conclude that in all acceptable spontaneous symmetry breaking schemes, cosmic string formation is unavoidable. The strings which form at the end of inflation have a mass which is proportional to the inflationary scale. Sometimes, a second network of strings form at a lower scale. Models based on gauge groups which have rank greater than 6 can lead to more than one inflationary era; they all end by cosmic string formation.

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arXiv1995

A Supersymmetric SO(10) Model with Inflation and Cosmic Strings

We have built a supersymmetric SO(10) model consistent with cosmological observations. The model gives rise to a false vacuum hybrid inflationary scenario which solves the monopole problem. We argue that this type of inflationary scenario is generic in supersymmetric SO(10) model, and arises naturally from the theory. Neither any external field nor any external symmetry has to be added. It can just be a consequence of the theory. In our specific model, at the end of inflation, cosmic strings form. The properties of the strings are presented. The cosmic background radiation anisotropies induced by the inflationary perturbations and the cosmic strings are estimated. The model produces a stable lightest superparticle and a very light left-handed neutrino which may serve as the cold and hot dark matter. The properties of a mixed cosmic string-inflationary large scale structure formation scenario are discussed.

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arXiv1995

Constraining Supersymmetric SO(10) Models Through Cosmology

We study the impact of the symmetry breaking patterns from supersymmetric SO(10) down to the standard model on the standard big-bang cosmology through the formation of topological defects. None of the models is consistent with the standard cosmology without invoking any mechanism to solve the monopole problem. For this purpose, we use a hybrid false vacuum inflationary scenario. Only two symmetry breaking patterns are consistent with these topological considerations and with the actual data on the proton lifetime.

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