Masiero, Antonio, Sorbo, Lorenzo
Academic Year, 2000/2001
Naturally inflating on steep potentials through electromagnetic dissipation (2009)
Anber, Mohamed M., Sorbo, Lorenzo
In models of natural inflation, the inflaton is an axion-like particle. Unfortunately, axion potentials in UV-complete theories appear to be too steep to drive inflation. We show that, even for a...
Primordial perturbations and non-Gaussianities from modulated trapping (2009)
Langlois, David, Sorbo, Lorenzo
We propose a new mechanism to generate primordial curvature perturbations, based on the resonant production of particles during inflation. It is known that this phenomenon can trap the inflaton for a...
Pauli-Fierz Gravitons on Friedmann-Robertson-Walker Background (2009)
We derive the Hamiltonian describing Pauli-Fierz massive gravitons on a flat Friedmann-Robertson-Walker (FRW) cosmology. The cosmological evolution is driven by a scalar field Phi with an arbitrary...
A Natural Framework for Chaotic Inflation (2008)
Kaloper, Nemanja, Sorbo, Lorenzo
We show that inflation with a quadratic potential occurs naturally in theories where an axion-like field mixes with a 4-form. Such an axion is massive, with the mass which arises from the mixing...
Where in the String Landscape is Quintessence (2008)
Kaloper, Nemanja, Sorbo, Lorenzo
We argue that quintessence may reside in certain corners of the string landscape. It arises as a linear combination of internal space components of higher rank forms, which are axion-like at low...
Higgsflation at the GUT scale in a Higgsless Universe (2008)
Kaloper, Nemanja, Sorbo, Lorenzo, Yokoyama, Jun'ichi
We revisit inflation in induced gravity. Our focus is on models where the low scale Planck mass is completely determined by the breaking of the scaling symmetry in the field theory sector. The...
Anber, Mohamed, Sorbo, Lorenzo
We provide the most general embedding of a purely tensional 2-brane in a 3+1 dimensional bulk described by the AdS C-metric. The AdS C-metric has been first considered as bulk metric by Emparan,...
Two gravitational shock waves on the AdS_3 brane (2007)
Anber, Mohamed, Sorbo, Lorenzo
A gravitational shock wave is a solution to Einstein equations describing the gravitational field of a massless particle. We obtain such a geometry for a particle moving on a AdS_3 brane embedded in...
Moduli from Cosmic Strings (2007)
Moduli fields are generally present in superstring--inspired models. They are typically characterized by masses of the order of the supersymmetry breaking scale and by interactions of gravitational...
Confronting pNGB quintessence with data (2006)
Dutta, Koushik, Sorbo, Lorenzo
We analyze the observational constraints on the model where a pseudo-Nambu-Goldstone boson (pNGB) plays the role of dark energy. The constraints are derived by using the latest Gold set of 182 type...
N-flationary magnetic fields (2006)
Anber, Mohamed M., Sorbo, Lorenzo
There is increasing interest in the role played by pseudo Nambu-Goldstone bosons (pNGBs) in the construction of string-inspired models of inflation. In these models the inflaton is expected to be...
Standard 4d gravity on a brane in six dimensional flux compactifications (2006)
Peloso, Marco, Sorbo, Lorenzo, Tasinato, Gianmassimo
We consider a six dimensional space-time, in which two of the dimensions are compactified by a flux. Matter can be localized on a codimension one brane coupled to the bulk gauge field and wrapped...
Kaloper, Nemanja, Sorbo, Lorenzo
We review the pNGB quintessence models, and point out that the reason why the large decay constants $f_a \ga {\cal O}(1)M_{Pl}$ are really needed is to tame a tachyonic instability present for a wide...
Locally Localized Gravity: The Inside Story (2005)
Kaloper, Nemanja, Sorbo, Lorenzo
We derive the exact gravitational field of a relativistic particle localized on an $AdS$ 3-brane, with curvature radius $\ell$, in $AdS_5$ bulk with radius $L$. The solution is a gravitational shock...
Moduli Entrapment with Primordial Black Holes (2004)
Kaloper, Nemanja, Rahmfeld, Joachim, Sorbo, Lorenzo
We argue that primordial black holes in the early universe can provide an efficient resolution of the Brustein-Steinhardt moduli overshoot problem in string cosmology. When the universe is created...
Observational Implications of Cosmological Event Horizons (2004)
Kaloper, Nemanja, Kleban, Matthew, Sorbo, Lorenzo
In a universe dominated by a small cosmological constant or by eternal dark energy with equation of state w < -1/3, observers are surrounded by event horizons. The horizons limit how much of the...
Can the universe afford inflation? (2004)
Albrecht, Andreas, Sorbo, Lorenzo
Cosmic inflation is envisioned as the ``most likely'' start for the observed universe. To give substance to this claim, a framework is needed in which inflation can compete with other scenarios and...
Moving sources in a ghost condensate (2004)
Ghost condensation has been recently proposed as a mechanism inducing the spontaneous breaking of Lorentz symmetry. Corrections to the Newton potential generated by a static source have been...
Goldberger-Wise variations: stabilizing brane models with a bulk scalar (2003)
Lesgourgues, Julien, Sorbo, Lorenzo
Braneworld scenarios with compact extra-dimensions need the volume of the extra space to be stabilized. Goldberger and Wise have introduced a simple mechanism, based on the presence of a bulk scalar...
Bulk gravitons from a cosmological brane (2003)
Langlois, David, Sorbo, Lorenzo
We investigate the emission of gravitons by a cosmological brane into an Anti de Sitter five-dimensional bulk spacetime. We focus on the distribution of gravitons in the bulk and the associated...
Leptogenesis and rescattering in supersymmetric models (2002)
Boubekeur, Lotfi, Davidson, Sacha, Peloso, Marco, Sorbo, Lorenzo
The observed baryon asymmetry of the Universe can be due to the $B-L$ violating decay of heavy right handed (s)neutrinos. The amount of the asymmetry depends crucially on their number density. If the...
Cosmology of a brane radiating gravitons into the extra dimension (2002)
Langlois, David, Sorbo, Lorenzo, Rodriguez-Martinez, Maria
We study in a self-consistent way the impact of the emission of bulk gravitons on the (homogeneous) cosmology of a three-brane embedded in a five-dimensional spacetime. In the low energy regime, we...
Moduli from Cosmic Strings (2002)
Moduli fields are generally present in superstring--inspired models. They are typically characterized by masses of the order of the supersymmetry breaking scale and by interactions of gravitational...
Effective action for the homogeneous radion in brane cosmology (2002)
Langlois, David, Sorbo, Lorenzo
We consider cosmological two-brane models with AdS bulk, for which the radion, i.e. the separation between the two branes, is time dependent. In the case of two de Sitter branes (including Minkowski...
Leptogenesis and rescattering in supersymmetric models (2002)
Boubekeur, Lotfi, Davidson, Sacha, Peloso, Marco, Sorbo, Lorenzo
Fermion production from preheating-amplified metric perturbations (2002)
Bassett, Bruce A., Peloso, Marco, Sorbo, Lorenzo, Tsujikawa, Shinji
We study gravitational creation of light fermions in the presence of classical scalar metric perturbations about a flat Friedmann-Lemaitre- Robertson-Walker (FLRW) background. These perturbations can...
Fermion production from preheating-amplified metric perturbations (2001)
Bassett, Bruce A., Peloso, Marco, Sorbo, Lorenzo, Tsujikawa, Shinji
We study gravitational creation of light fermions in the presence of classical scalar metric perturbations about a flat Friedmann-Lemaitre- Robertson-Walker (FLRW) background. These perturbations can...
Coupled fields in external background with application to nonthermal production of gravitinos (2001)
Nilles, Hans Peter, Peloso, Marco, Sorbo, Lorenzo
We provide the formalism for the quantization of systems of coupled bosonic and fermionic fields in a time dependent classical background. The occupation numbers of the particle eigenstates can be...
Nonthermal production of gravitinos and inflatinos (2001)
Nilles, Hans Peter, Peloso, Marco, Sorbo, Lorenzo
We explicitly calculate nonthermal gravitino production during the preheating period in the inflationary Universe. Contrary to earlier investigations, we consider a two--field model to separate the...
Coupled fields in external background with application to nonthermal production of gravitinos (2001)
Nilles, Hans Peter, Peloso, Marco, Sorbo, Lorenzo
We provide the formalism for the quantization of systems of coupled bosonic and fermionic fields in a time dependent classical background. The occupation numbers of the particle eigenstates can be...
Cosmology of the Randall-Sundrum model after dilaton stabilization (2000)
Lesgourgues, Julien, Pastor, Sergio, Peloso, Marco, Sorbo, Lorenzo
We provide the first complete analysis of cosmological evolution in the Randall-Sundrum model with stabilized dilaton. We give the exact expansion law for matter densities on the two branes with...
Baryogenesis vs. proton stability in theories with extra dimensions (2000)
Masiero, Antonio, Peloso, Marco, Sorbo, Lorenzo, Tabbash, Rula
We propose a new scenario of baryogenesis in the context of theories with large extra dimensions. The baryon number is almost conserved at zero temperature by means of a localization mechanism...
Cosmology of the Randall-Sundrum model after dilaton stabilization (2000)
Lesgourgues, Julien, Pastor, Sergio, Peloso, Marco, Sorbo, Lorenzo
Effective action for Dirac spinors in the uniform electromagnetic background fields (1998)
Soldati, Roberto, Sorbo, Lorenzo
Some new expressions are found, concerning the effective action as a regularized path-integral for Dirac's spinors in {\it 3+1} dimensions, in the presence of general uniform (i.e., constant and...
Effective action for Dirac spinors in the presence of general uniform electromagnetic fields (1998)
Soldati, Roberto, Sorbo, Lorenzo
Some new expressions are found, concerning the one-loop effective action of four dimensional massive and massless Dirac fermions in the presence of general uniform electric and magnetic fields, with...