M. Gasperini

Why supersymmetry should be restored at the TeV scale (2008)

The vacuum energy density arising from the broken supersymmetry of the (standard-model) fields living on a brane cannot be fully "off-loaded" to the bulk: even assuming the existence of an effective...

Dilaton Cosmology and Phenomenology (2008)

It is explained why the curvature associated to the vacuum energy density arising from SUSY breaking cannot be completely transferred to the extra spatial dimensions of a bulk space-time manifold,...

BA-TH/04-491 Bicocca-FT-04-9 astro-ph/0407573 Fitting Type Ia supernovae (2008)

Summary. This paper is dedicated to Gabriele Veneziano on his 65th birthday. Most of the results reported here are known results, due to Gabriele, or obtained in collaboration with him, or inspired...

L. Amendola, M. Gasperini, F. Piazza

with coupled dark energy

Perturbations in a non-singular bouncing Universe (2008)

M. Gasperini, M. Giovannini, G. Veneziano, Istituto Nazionale, Fisica Nucleare, Sezione Di Bari

hep-th/0306113

(Frontier Collection Series, Springer-Verlag, Heidelberg, 2007) String theory and pre-big bang cosmology (2008)

M. Gasperini, G. Veneziano, M. Gasperini, G. Veneziano, Istituto Nazionale, Fisica Nucleare, ...

Summary. In string theory, the traditional picture of a Universe that emerges from the inflation of a very small and highly curved space-time patch is a possibility, not a necessity: quite different...

Non-local dilaton coupling to dark matter: cosmic acceleration and pressure backreaction (2007)

Amendola, L., Gasperini, M., Ungarelli, C.

A model of non-local dilaton interactions, motivated by string duality symmetries, is applied to a scenario of "coupled quintessence" in which the dilaton dark energy is non-locally coupled to the...

PRODUCTION AND DETECTION OF RELIC DILATONS IN STRING COSMOLOGY (2007)

Signal-to-Noise Ratio for a Stochastic Background of Massive Relic Particles (2007)

This paper summarizes the contribution presented at the IX Marcel

Gasperini Dipartimento Di, M. Gasperini

We estimate the signal-to-noise ratio for two gravitational detectors interacting with a stochastic background of massive scalar waves. We find that the present experimental level of sensitivity...

Birth of the Universe as anti-tunnelling from the string perturbative vacuum (2007)

Gasperini Dipartimento Di, M. Gasperini

The decay of the string perturbative vacuum, if triggered by a suitable, duality-breaking dilaton potential, can efficiently proceed via the parametric amplification of the Wheeler-De Witt wave...

Normal Modes for Metric Fluctuations in a Class of Higher-Dimensional Backgrounds (2007)

Quantum Squeezing and Cosmological Entropy Production (2007)

We discuss a gauge invariant approach to the theory of cosmological perturbations in a higher-dimensonal background. We find the normal modes which diagonalize the perturbed action, for a scalar...

Gasperini Theory, M. Gasperini, M. Giovannini

The entropy growth in a cosmological process of pair production is completely determined by the associated squeezing parameter, and is insensitive to the number of particles in the initial state. The...

DFTT-38/90 December 1990 KINEMATIC INTERPRETATION OF STRING INSTABILITY IN A BACKGROUND GRAVITATIONAL FIELD (2007)

Gasperini Dipartimento, M. Gasperini

The unstable regime in which the string oscillating modes develop imaginary frequencies is shown to be characterized, kinematically, by a positive relative acceleration among the different points of...

Expanding And Contracting Universes In Third Quantized String Cosmology (2007)

Buonanno Gasperini, A. Buonanno, M. Gasperini, M. Maggiore, C. Ungarelli

We discuss the possibility of quantum transitions from the string perturbative vacuum to cosmological configurations characterized by isotropic contraction and decreasing dilaton. When the dilaton...

(1) (2007)

M. Gasperini, C. Ungarelli

gr-qc/0103035

BA-TH/02-454 gr-qc/0301032 Phenomenology of the relic dilaton background (2007)

Gasperini Dipartimento Di, M. Gasperini, Maurizio Gasperini

We discuss the expected amplitude of a cosmic background of massive, non-relativistic dilatons, and we report recent results about its possible detection. This paper is a contracted version of a talk...

FT/UCM/01/96 gr-qc/9604002 Normal Modes for Metric Fluctuations (2007)

In Class Of, M. Gasperini, M. Giovannini

We discuss a gauge invariant approach to the theory of cosmological perturbations in a higher-dimensonal background. We find the normal modes which diagonalize the perturbed action, for a scalar...

On the Response of Gravitational Antennas to Dilatonic Waves (2007)

Gasperini Dipartimento Di, M. Gasperini

It is pointed out that the coupling of macroscopic test masses to the gravidilaton background of string theory is non geodesic, in general, and cannot be parametrized by a Brans-Dicke model of...

Low-energy graceful exit in anisotropic string cosmology backgrounds (2007)

G. De Risi, M. Gasperini

We discuss the possibility of a smooth transition from the pre- to the post-big bang regime, in the context of the lowest-order string effective action (without higher-derivative corrections), taking...

Assisting Pre-Big Bang Phenomenology Through Short-Lived Axions (2007)

V. Bozza, M. Gasperini, M. Giovannini, G. Veneziano

We present the results of a detailed study of how isocurvature axion fluctuations are converted into adiabatic metric perturbations through axion decay, and discuss the constraints on the parameters...

String Theory and Pre-big bang Cosmology (2007)

String Theory and Pre-big bang Cosmology (2007)

In string theory, the traditional picture of a Universe that emerges from the inflation of a very small and highly curved space-time patch is a possibility, not a necessity: quite different initial...

Dilaton cosmology and phenomenology (2007)

In string theory, the traditional picture of a Universe that emerges from the inflation of a very small and highly curved space-time patch is a possibility, not a necessity: quite different initial...

A new scale in the sky (2006)

This paper is dedicated to Gabriele Veneziano on his 65th birthday. Most of the results reported here are known results, due to Gabriele, or obtained in collaboration with him, or inspired by our...

A new scale in the sky (2006)

The existence of a new ultraviolet scale $\Lambda=g M_P$ for effective theories with gravity and U(1) gauge fields has recently been conjectured as a possible criterion for distinguishing parts of...

SNLS data are consistent with acceleration at z=3 (2006)

The existence of a new ultraviolet scale $\Lambda=g M_P$ for effective theories with gravity and U(1) gauge fields has recently been conjectured as a possible criterion for distinguishing parts of...

Amendola, Luca, Gasperini, M., Piazza, Federico

We point out that the Type Ia supernovae in the SNLS dataset are consistent with an early beginning of the cosmic acceleration if dark energy interacts strongly with dark matter. We find that the...

Observable (?) cosmological signatures of superstring models (2005)

Gasperini, M, Nicotri, S

The different couplings of the dilaton to the U(1) gauge field of heterotic and Type I superstrings may leave an imprint on the relics of the very early cosmological evolution. We discuss the...

Observable (?) cosmological signatures of superstrings in pre-big bang models of inflation (2005)

Gasperini, M., Nicotri, S.

The different couplings of the dilaton to the U(1) gauge field of heterotic and Type I superstrings may leave an imprint on the relics of the very early cosmological evolution. Working in the context...

Primordial magnetic seeds from string cosmology (2005)

Primordial magnetic seeds from string cosmology (2005)

After a discussion of the inflationary production of primordial magnetic seeds, and a short review of various possible mechanisms, we concentrate on the analysis of the photon-dilaton coupling...

Response of the common mode of interferometric detectors to a stochastic background of massive scalar radiation (2005)

After a discussion of the inflationary production of primordial magnetic seeds, and a short review of various possible mechanisms, we concentrate on the analysis of the photon-dilaton coupling...

Bonasia, N., Gasperini, M.

We compute the angular pattern and the overlap reduction functions for the geodesic and non-geodesic response of the common mode of two interferometers interacting with a stochastic, massive scalar...

Relic gravitons on Kasner-like branes (2005)

Cavaglia', M., De Risi, G., Gasperini, M.

We discuss the cosmological amplification of tensor perturbations in a simple example of brane-world scenario, in which massless gravitons are localized on a higher-dimensional Kasner-like brane...

Texture prediction of an AA3004 alumium alloy with the occurrence of strain localization during simple shear using a multiscale modeling procedure (2005)

Gasperini, M, Van Houtte, Paul; U0013123

Although the Taylor-type models gives reasonable texture prediction of the monotonic cold deformation of annealed aluminum alloys both qualitatively and quantitatively, results are less satisfactory...

Strain localization observed during shearing of some aluminium alloys and texture softening predicted by FC Taylor and Adavanced Lamel Model (2005)

Gasperini, M, Van Houtte, Paul; U0013123

In-situ SEM shearing tests were performed on samples from the heavily cold rolled (Extra-hard) aluminium alloys, where the parallelepiped test sample was cut as to let shear direction (SD) have an...

Towards a future singularity? (2004)

Cosmological perturbations across a curvature bounce (2004)

We discuss whether the future extrapolation of the present cosmological state may lead to a singularity even in case of "conventional" (negative) pressure of the dark energy field, namely $w=p/\rho...

Gasperini, M, Giovannini, Massimo, Veneziano, Gabriele

String-inspired cosmologies, whereby a non-singular curvature bounce is induced by a general-covariant, $T$-duality-invariant, non-local dilaton potential, are used to study numerically how...

Cosmological perturbations across a curvature bounce (2004)

Late-time effects of Planck-scale cosmology: dilatonic interpretation of the dark energy field (2003)

String-inspired cosmologies, whereby a non-singular curvature bounce is induced by a general-covariant, $T$-duality-invariant, non-local dilaton potential, are used to study numerically how...

Perturbations in a non-singular bouncing Universe (2003)

We present a model of dark energy based on the string effective action, and on the assumption that the dilaton is strongly coupled to dark matter. We discuss the main differences between this class...

Gasperini, M, Giovannini, Massimo, Veneziano, Gabriele

We complement the low-energy gravi-dilaton effective action of string theory with a non-local, general-covariant dilaton potential, and obtain homogeneous solutions describing a non-singular...

Perturbations in a non-singular bouncing Universe (2003)

Phenomenology of the relic dilaton background (2003)

We complement the low-energy gravi-dilaton effective action of string theory with a non-local, general-covariant dilaton potential, and obtain homogeneous solutions describing a non-singular...

Perturbations in a non-singular bouncing Universe (2003)

We discuss the expected amplitude of a cosmic background of massive, non-relativistic dilatons, and we report recent results about its possible detection. This paper is a contracted version of a talk...

M. Gasperini, M. Giovannini, G. Veneziano

We complement the low-energy gravi-dilaton e#ective action of string theory with a non-local, general-covariant dilaton potential, and obtain homogeneous solutions describing a non-singular...

Constraints on pre-big bang parameter space from CMBR anisotropies (2002)

Bozza, Valerio, Gasperini, M, Giovannini, Massimo, Veneziano, Gabriele

The so-called curvaton mechanism --a way to convert isocurvature perturbations into adiabatic ones-- is investigated both analytically and numerically in a pre-big bang scenario where the role of the...

Constraints on pre-big bang parameter space from CMBR anisotropies (2002)

Bozza, V., Gasperini, M., Giovannini, M., Veneziano, G.

The so-called curvaton mechanism --a way to convert isocurvature perturbations into adiabatic ones-- is investigated both analytically and numerically in a pre-big bang scenario where the role of the...

Early acceleration and adiabatic matter perturbations in a class of dilatonic dark-energy models (2002)

Amendola, L., Gasperini, M., Tocchini-Valentini, D., Ungarelli, C.

We estimate the growth of matter perturbations in a class of recently proposed dark-energy models based on the (loop-corrected) gravi-dilaton string effective action, and characterized by a global...

The Pre-Big Bang Scenario in String Cosmology (2002)

The Pre-Big Bang Scenario in String Cosmology (2002)

We review physical motivations, phenomenological consequences, and open problems of the so-called pre-big bang scenario in superstring cosmology.

Assisting pre-big bang phenomenology through short-lived axions (2002)

We review physical motivations, phenomenological consequences, and open problems of the so-called pre-big bang scenario in superstring cosmology.

Bozza, Valerio, Gasperini, M, Giovannini, Massimo, Veneziano, Gabriele

We present the results of a detailed study of how isocurvature axion fluctuations are converted into adiabatic metric perturbations through axion decay, and discuss the constraints on the parameters...

Assisting pre-big bang phenomenology through short-lived axions (2002)

Bozza, V., Gasperini, M., Giovannini, M., Veneziano, G.

We present the results of a detailed study of how isocurvature axion fluctuations are converted into adiabatic metric perturbations through axion decay, and discuss the constraints on the parameters...

Constraints on pre-big bang parameter space from CMBR anisotropies (2002)

V. Bozza, M. Gasperini, M. Giovannini, G. Veneziano

The so-called curvaton mechanism --a way to convert isocurvature perturbations into adiabatic ones-- is investigated both analytically and numerically in a pre-big bang scenario where the role of the...

Scalar fluctuations in dilatonic brane-worlds (2001)

Bozza, Valerio, Gasperini, M, Veneziano, Gabriele

We derive and solve the full set of scalar perturbation equations for a class of five-dimensional brane--world solutions, with a dilaton scalar field coupled to the bulk cosmological constant and to...

Scalar fluctuations in dilatonic brane-worlds (2001)

Bozza, V., Gasperini, M., Veneziano, G.

We derive and solve the full set of scalar perturbation equations for a class of five-dimensional brane--world solutions, with a dilaton scalar field coupled to the bulk cosmological constant and to...

Low-energy graceful exit in anisotropic string cosmology backgrounds (2001)

De Risi, G., Gasperini, M.

We discuss the possibility of a smooth transition from the pre- to the post-big bang regime, in the context of the lowest-order string effective action (without higher-derivative corrections), taking...

Quintessence as a run-away dilaton (2001)

Gasperini, M, Piazza, F, Veneziano, Gabriele

We consider a late-time cosmological model based on a recent proposal that the infinite-bare-coupling limit of superstring/M-theory exists and has good phenomenological properties, including a...

Quintessence as a run-away dilaton (2001)

Gasperini, M., Piazza, F., Veneziano, G.

We consider a late-time cosmological model based on a recent proposal that the infinite-bare-coupling limit of superstring/M-theory exists and has good phenomenological properties, including a...

Sensitivity of spherical gravitational-wave detectors to a stochastic background of non-relativistic scalar radiation (2001)

Coccia, E., Gasperini, M., Ungarelli, C.

We analyze the signal-to-noise ratio for a relic background of scalar gravitational radiation composed of massive, non-relativistic particles, interacting with the monopole mode of two resonant...

Localization of Scalar Fluctuations in a Dilatonic Brane-World Scenario (2001)

Bozza, Valerio, Gasperini, M, Veneziano, Gabriele

We derive and solve the full set of scalar perturbation equations for a class of $Z_2$-symmetric five-dimensional geometries generated by a bulk cosmological constant and by a 3-brane non-minimally...

Localization of Scalar Fluctuations in a Dilatonic Brane-World Scenario (2001)

Bozza, V., Gasperini, M., Veneziano, G.

We derive and solve the full set of scalar perturbation equations for a class of $Z_2$-symmetric five-dimensional geometries generated by a bulk cosmological constant and by a 3-brane non-minimally...

Dilatonic Interpretation of the Quintessence? (2001)

Detecting a relic background of scalar waves with LIGO (2001)

We discuss the possibility that "quintessential effects", recently displayed by large scale observations, may be consistently described in the context of the low-energy string effective action, and...

Gasperini, M., Ungarelli, C.

We discuss the possible detection of a stochastic background of massive, non-relativistic scalar particles, through the cross correlation of the two LIGO interferometers in the initial, enhanced and...

A diagrammatic approach to the spectrum of cosmological perturbations (2001)

De Risi, G., Gasperini, M.

We compute the spectral distribution of the quantum fluctuations of the vacuum, amplified by inflation, after an arbitrary number of background transitions. Using a graphic representation of the...

Gravitational waves in non-singular string cosmologies (2001)

Cartier, C., Copeland, E. J., Gasperini, M.

We study the evolution of tensor metric fluctuations in a class of non-singular models based on the string effective action, by including in the perturbation equation the higher-derivative and loop...

Localization of Scalar Fluctuations in a Dilatonic Brane-World Scenario (2001)

V. Bozza, M. Gasperini, G. Veneziano, E. R. Caianiello

We derive and solve the full set of scalar perturbation equations for a class of Z 2 - symmetric five-dimensional geometries generated by a bulk cosmological constant and by a 3-brane non-minimally...

Quintessence as a Run-Away Dilaton (2001)

M. Gasperini, F. Piazza, G. Veneziano

We consider a late-time cosmological model based on a recent proposal that the in nite-bare-coupling limit of superstring/M-theory exists and has good phenomenological properties, including a...

New mechanism for the generation of primordial seeds for the cosmic magnetic fields (2000)

Production and detection of relic dilatons in string cosmology (2000)

We discuss the inflationary production of magnetic seeds for the galactic dynamo through the photon-graviphoton mixing typical of extended models of local supersymmetry. An analisys of the allowed...

String cosmology versus standard and inflationary cosmology (2000)

This paper summarizes the contribution presented at the {\sl IX Marcel Grossmann Meeting} (Rome, July 2000). It is stressed, in particular, that a non-relativistic background of ultra-light dilatons,...

Birth of the Universe as anti-tunnelling from the string perturbative vacuum (2000)

This paper presents a review of the basic, model-independent differences between the pre-big bang scenario, arising naturally in a string cosmology context, and the standard inflationary scenario. We...

Signal-to-noise ratio for a stochastic background of massive relic particles (2000)

The decay of the string perturbative vacuum, if triggered by a suitable, duality-breaking dilaton potential, can efficiently proceed via the parametric amplification of the Wheeler-De Witt wave...

On the response of gravitational antennas to dilatonic waves (1999)

We estimate the signal-to-noise ratio for two gravitational detectors interacting with a stochastic background of massive scalar waves. We find that the present experimental level of sensitivity...

Elementary introduction to pre-big bang cosmology and to the relic graviton background (1999)

It is pointed out that the coupling of macroscopic test masses to the gravi-dilaton background of string theory is non geodesic, in general, and cannot be parametrized by a Brans-Dicke model of...

Looking back in time beyond the big bang (1999)

This is a contracted version of a series of lectures for graduate and undergraduate students given at the {\sl ``VI Seminario Nazionale di Fisica Teorica"} (Parma, September 1997), at the Second Int....

Inflation and initial conditions in the pre-big bang scenario (1999)

String theory can (in principle) describe gravity at all curvature scales, and can be applied to cosmology to look back in time beyond the Planck epoch. The duality symmetries of string theory...

Looking Back in Time beyond the Big Bang (1999)

The pre-big bang scenario describes the evolution of the Universe from an initial state approaching the flat, cold, empty, string perturbative vacuum. The choice of such an initial state is suggested...

Weighing the string mass with the COBE data (1998)

String theory can (in principle) describe gravity at all curvature scales, and can be applied to cosmology to look back in time beyond the Planck epoch. The duality symmetries of string theory...

Constraints on pre-big bang models for seeding large-scale anisotropy by massive Kalb-Ramond axions (1998)

In the context of the pre-big bang scenario the large-scale CMB anisotropy can be seeded by a primordial background of very light (or massless) axion fluctuations. In that case the slope of the...

Constraints on pre-big bang models for seeding large-scale anisotropy by massive Kalb-Ramond axions (1998)

We discuss the conditions under which pre-big bang models can fit the observed large-scale anisotropy with a primordial spectrum of massive (Kalb--Ramond) axion fluctuations. The primordial spectrum...

Massless (pseudo-)scalar seeds of CMB anisotropy (1998)

We discuss the conditions under which pre-big bang models can fit the observed large-scale anisotropy with a primordial spectrum of massive (Kalb--Ramond) axion fluctuations. The primordial spectrum...

Durrer, R, Gasperini, M, Sakellariadou, M, Veneziano, Gabriele

A primordial stochastic background of very weakly coupled massless (pseudo-)scalars can seed CMB anisotropy, when large-scale fluctuations of their stress-tensor re-enter the horizon during the...

Massless (pseudo-)scalar seeds of CMB anisotropy (1998)

Durrer, R., Gasperini, M., Sakellariadou, M., Veneziano, G.

A primordial stochastic background of very weakly coupled massless (pseudo-)scalars can seed CMB anisotropy, when large-scale fluctuations of their stress-tensor re-enter the horizon during the...

Repulsive gravity in the very early Universe (1998)

Seeds of large-scale anisotropy in string cosmology (1998)

I present two examples in which the curvature singularity of a radiation-dominated Universe is regularized by (a) the repulsive effects of spin interactions, and (b) the repulsive effects arising...

Durrer, R, Gasperini, M, Sakellariadou, M, Veneziano, Gabriele

Pre-big bang cosmology predicts tiny first-order dilaton and metric perturbations at very large scales. Here we discuss the possibility that other -- more copiously generated -- perturbations may...

Seeds of large-scale anisotropy in string cosmology (1998)

Durrer, R., Gasperini, M., Sakellariadou, M., Veneziano, G.

Pre-big bang cosmology predicts tiny first-order dilaton and metric perturbations at very large scales. Here we discuss the possibility that other -- more copiously generated -- perturbations may...

Duality in cosmological perturbation theory (1998)

Brustein, Ram, Gasperini, M, Veneziano, Gabriele

Cosmological perturbation equations derived from low-energy effective actions are shown to be invariant under a duality transformation reminiscent of electric-magnetic, strong-weak coupling,...

Duality in cosmological perturbation theory (1998)

Brustein, R., Gasperini, M., Veneziano, G.

Cosmological perturbation equations derived from low-energy effective actions are shown to be invariant under a duality transformation reminiscent of electric-magnetic, strong-weak coupling,...

Repulsive gravity in the very early Universe (1998)

Testing string cosmology with gravity wave detectors (1997)

I present two examples in which the curvature singularity of a radiationdominated Universe is regularized by (a) the repulsive effects of spin interactions, and (b) the repulsive effects arising from...

A class of non-singular gravi-dilaton backgrounds (1997)

The general properties of the gravity wave backgrounds of cosmological origin are reviewed and briefly discussed, with emphasis on the relic background expected from an early pre-big bang phase...

Buonanno, A, Gasperini, M, Ungarelli, C

We present a class of static, spherically symmetric, non-singular solutions of the tree-level string effective action, truncated to first order in 0$ and $r\to \infty$) two different anti-de Sitter...

A class of non-singular gravi-dilaton backgrounds (1997)

Buonanno, A., Gasperini, M., Ungarelli, C.

We present a class of static, spherically symmetric, non-singular solutions of the tree-level string effective action, truncated to first order in $\alpha'$. In the string frame the solutions...

Birth of the Universe in string cosmology (1997)

Low-energy quantum string cosmology (1997)

The decay of the string perturbative vacuum into our present cosmological state is associated to the transition from a phase of growing curvature and growing dilaton, to a phase of decreasing...

Tensor perturbations in high-curvature string backgrounds (1997)

We introduce a Wheeler-De Witt approach to quantum cosmology based on the low-energy string effective action, with an effective dilaton potential included to account for non-perturbative effects and,...

Expanding and contracting universes in third quantized string cosmology (1997)

We derive a generalized equation for the evolution of tensor perturbations in a cosmological background, taking into account higher-curvature contributions and a tree-level coupling to the dilaton in...

Buonanno, A, Gasperini, M, Maggiore, Michele, Ungarelli, C

We discuss the possibility of quantum transitions from the string perturbative vacuum to cosmological configurations characterized by isotropic contraction and decreasing dilaton. When the dilaton...

Expanding and contracting universes in third quantized string cosmology (1997)

Buonanno, A., Gasperini, M., Maggiore, M., Ungarelli, C.

We discuss the possibility of quantum transitions from the string perturbative vacuum to cosmological configurations characterized by isotropic contraction and decreasing dilaton. When the dilaton...

Relic dilatons in string cosmology (1996)

Relic dilatons in string cosmology (1996)

The allowed mass windows for a cosmic background of relic dilatons are estimated in the context of the pre-big bang scenario. The dilatons are produced from the quantum fluctuations of the vacuum,...

Towards a non-singular pre-Big Bang cosmology (1996)

The allowed mass windows for a cosmic background of relic dilatons are estimated in the context of the pre-big bang scenario. The dilatons are produced from the quantum fluctuations of the vacuum,...

Gasperini, M, Maggiore, Michele, Veneziano, Gabriele

We discuss general features of the $\beta$-function equations for spatially flat, $(d+1)$-dimensional cosmological backgrounds at lowest order in the string-loop expansion, but to all orders in...

Towards a non-singular pre-big bang cosmology (1996)

Gasperini, M., Maggiore, M., Veneziano, G.

We discuss general features of the $\beta$-function equations for spatially flat, $(d+1)$-dimensional cosmological backgrounds at lowest order in the string-loop expansion, but to all orders in...

Relic gravitons from the pre-big bang: what we know and what we do not know (1996)

Singularity and exit problems in two-dimensional string cosmology (1996)

I discuss the status of present knowledge about a possible background of relic gravitons left by an early, pre-big bang cosmological epoch, whose existence in the past of our Universe is suggested by...

Relic gravitons from the pre-big bang: what we know and what we do not know (1996)

A broad class of two-dimensional loop-corrected dilaton gravity models exhibit cosmological solutions that interpolate between the string perturbative vacuum and a background with asymptotically flat...

Singularity and exit problems in two-dimensional string cosmology (1996)

I discuss the status of present knowledge about a possible background of relic gravitons left by an early, pre-big bang cosmological epoch, whose existence in the past of our Universe is suggested by...

Peak and end point of the relic graviton background in string cosmology (1996)

A broad class of two-dimensional loop-corrected dilaton gravity models exhibit cosmological solutions that interpolate between the string perturbative vacuum and a background with asymptotically flat...

Brustein, Ram, Gasperini, M, Veneziano, Gabriele

Using general arguments we determine the allowed region for the end point frequency and the peak energy density of the stochastic background of gravity waves expected in string cosmology. We provide...

Peak and end point of the relic graviton background in string cosmology (1996)

Brustein, R., Gasperini, M., Veneziano, G.

Using general arguments we determine the allowed region for the end point frequency and the peak energy density of the stochastic background of gravity waves expected in string cosmology. We provide...

Normal modes for metric fluctuations in a class of anisotropic backgrounds (1996)

Gasperini, M, Giovannini, Massimo

We relax the assumption of isotropy of the background manifold in the gauge invariant approach to the theory of cosmological perturbations. We find the normal modes which diagonalize the perturbed...

Normal modes for metric fluctuations in a class of higher-dimensional backgrounds (1996)

Graceful exit in quantum string cosmology (1996)

We discuss a gauge invariant approach to the theory of cosmological perturbations in a higher-dimensonal background. We find the normal modes which diagonalize the perturbed action, for a scalar...

Gasperini, M, Maharana, J P, Veneziano, Gabriele

We write an O(d,d)-covariant Wheeler-De Witt equation in the (d^2+1)-dimensional minisuperspace of low-energy cosmological string backgrounds. We discuss explicit examples of transitions between two...

Birth of the universe as quantum scattering in string cosmology (1996)

Birth of the Universe as quantum scattering in string cosmology (1996)

In a Wheeler-de Witt approach to quantum string cosmology, the present state of the Universe arises from the scattering and reflection of the wave function representing the initial string vacuum in...

Graceful exit in quantum string cosmology (1996)

In a Wheeler-de Witt approach to quantum string cosmology, the present state of the Universe arises from the scattering and reflection of the wave function representing the initial string vacuum in...

Gasperini, M., Maharana, J., Veneziano, G.

We write an O(d,d)-covariant Wheeler-De Witt equation in the ($d^2+1$)-dimensional minisuperspace of low-energy cosmological string backgrounds. We discuss explicit examples of transitions between...

Tettonica dell'Adriatico meridionale (1996)

Argnani, A.; Ist. Geologia Marina, CNR, Bologna, Italia, Favali, P.; Istituto Nazionale Di Geofisica E Vulcanologia, Sezione Roma2, Roma, Italia, Frugoni, F.; Istituto Nazionale Di Geofisica E Vulcanologia, Sezione Roma2, Roma, Italia, Gasperini, M.; Ist. Geologia Marina, CNR, Bologna, Italia, Ligi, M.; Ist. Geologia Marina, CNR, Bologna, Italia, Marani, M.; Ist. Geologia Marina, CNR, Bologna, Italia, ...

L'evoluzione tettonica delllAdriatico meridionale Ã stata studiata attraverso l'interpretazione di profili sismici a riflessione e l'analisi di pozzi per l'esplorazione. Durante il Mesozoico...

Peak and End Point of the Relic Graviton Background in String Cosmology (1996)

R. Brustein, M. Gasperini, G. Veneziano

Using general arguments we determine the allowed region for the end point frequency and the peak energy density of the stochastic background of gravity waves expected in string cosmology. We provide...

Towards A Non-Singular Pre-Big Bang Cosmology (1996)

M. Gasperini, M. Maggiore, G. Veneziano

We discuss general features of the beta-function equations for spatially flat, (d + 1)-dimensional cosmological backgrounds at lowest order in the string-loop expansion, but to all orders in...

Singularity And Exit Problems In Two-Dimensional String Cosmology (1996)

Gasperini And, M. Gasperini, G. Veneziano

A broad class of two-dimensional loop-corrected dilaton gravity models exhibit cosmological solutions that interpolate between the string perturbative vacuum and a background with asymptotically flat...

Birth of the Universe as Quantum Scattering in String Cosmology (1996)

Peak and End Point of the Relic Graviton Background in String Cosmology (1996)

In a Wheeler-De Witt approach to quantum string cosmology, the present state of the Universe arises from the scattering and reflection of the wave function representing the initial string vacuum in...

R. Brustein, M. Gasperini, G. Veneziano

Using general arguments we determine the allowed region for the end point frequency and the peak energy density of the stochastic background of gravity waves expected in string cosmology. We provide...

Expanding And Contracting Universes In Third Quantized String Cosmology (1996)

A. Buonanno, M. Gasperini, M. Maggiore, C. Ungarelli

We discuss the possibility of quantum transitions from the string perturbative vacuum to cosmological configurations characterized by isotropic contraction and decreasing dilaton. When the dilaton...

Graceful Exit In Quantum String Cosmology (1996)

Towards A Non-Singular Pre-Big Bang Cosmology (1996)

We write an O(d, d)-covariant Wheeler-De Witt equation in the (d of low-energy cosmological string backgrounds. We discuss explicit examples of transitions between two duality-related cosmological...

M. Gasperini, M. Maggiore, G. Veneziano

We discuss general features of the fi-function equations for spatially flat, (d + 1)-dimensional cosmological backgrounds at lowest order in the string-loop expansion, but to all orders in . In the...

Gravitational radiation from string cosmology (1995)

Brustein, Ram, Gasperini, M, Giovannini, Massimo, Veneziano, Gabriele

A spectrum of relic stochastic gravitational radiation, strongly tilted towards high frequencies, and characterized by two basic parameters is shown to emerge in a class of string theory models. We...

Gravitational Radiation from String Cosmology (1995)

Brustein, R., Gasperini, M., Giovannini, M., Veneziano, G.

A spectrum of relic stochastic gravitational radiation, strongly tilted towards high frequencies, and characterized by two basic parameters is shown to emerge in a class of string theory models. We...

Status of String Cosmology: Phenomenological Aspects (1995)

Relic gravitational waves from string cosmology (1995)

I report recent studies on the evolution of perturbations in the context of the ``pre-big-bang" scenario typical of string cosmology, with emphasis on the formation of a stochastic background of...

Brustein, Ram, Gasperini, M, Giovannini, Massimo, Veneziano, Gabriele

A large class of string-cosmology backgrounds leads to a spectrum of relic stochastic gravitational waves, strongly tilted towards high frequencies, and characterized by two basic parameters of the...

Relic Gravitational Waves from String Cosmology (1995)

Brustein, R., Gasperini, M., Giovannini, M., Veneziano, G.

A large class of string-cosmology backgrounds leads to a spectrum of relic stochastic gravitational waves, strongly tilted towards high frequencies, and characterized by two basic parameters of the...

Amplification of Vacuum Fluctuations in String Cosmology Backgrounds (1995)

Electromagnetic origin of the CMB anisotropy in string cosmology (1995)

Inflationary string cosmology backgrounds can amplify perturbations in a more efficient way than conventional inflationary backgrounds, because the perturbation amplitude may grow - instead of being...

Gasperini, M, Giovannini, Massimo, Veneziano, Gabriele

In the inflationary scenarios suggested by string theory, the vacuum fluctuations of the electromagnetic field can be amplified by the time-evolution of the dilaton background, and can grow large...

Electromagnetic Origin of the CMB Anisotropy in String Cosmology (1995)

Primordial magnetic fields from string cosmology (1995)

In the inflationary scenarios suggested by string theory, the vacuum fluctuations of the electromagnetic field can be amplified by the time-evolution of the dilaton background, and can grow large...

Gasperini, M, Giovannini, Massimo, Veneziano, Gabriele

Sufficiently large seeds for generating the observed (inter)galactic magnetic fields emerge naturally in string cosmology from the amplification of electromagnetic vacuum fluctuations due to a...

Primordial Magnetic Fields From String Cosmology (1995)

GasperinI, M., Giovannini, M., Veneziano, G.

Sufficiently large seeds for generating the observed (inter)galactic magnetic fields emerge naturally in string cosmology from the amplification of electromagnetic vacuum fluctuations due to a...

Evolution of a string network in backgrounds with rolling horizons (1995)

Gasperini, M, Giovannini, Massimo, Meissner, K A, Veneziano, Gabriele

We discuss the temporal variation of the equation of state of a classical string network, evolving in a background in which the Hubble radius 1/H shrinks to a minimum and then re-expands to infinity....

EVOLUTION OF A STRING NETWORK IN BACKGROUNDS WITH ROLLING HORIZONS (1995)

Gasperini, M., Giovannini, M., Meissner, K. A., Veneziano, G.

We discuss the temporal variation of the equation of state of a classical string network, evolving in a background in which the Hubble radius 1/H shrinks to a minimum and then re-expands to infinity....

Von Neumann and Shannon-Wehrl entropy for squeezed states and cosmological particle production (1995)

Gasperini, M, Giovannini, Massimo

We show that the effective coarse graining of a two-mode squeezed density matrix, implicit in the Wehrl approaches to a semiclassical phase-space distribution, leads to results in agreement with...

VON NEUMANN AND SHANNON-WEHRL ENTROPY FOR SQUEEZED STATES AND COSMOLOGICAL PARTICLE PRODUCTION (1995)

Metric perturbations in dilaton-driven inflation (1995)

We show that the effective coarse graining of a two-mode squeezed density matrix, implicit in the Wehrl approaches to a semiclassical phase-space distribution, leads to results in agreement with...

Brustein, Ram, Gasperini, M, Giovannini, Massimo, Mukhanov, V F, Veneziano, Gabriele

We compute the spectrum of scalar and tensor metric perturbations generated, as amplified vacuum fluctuations, during an epoch of dilaton-driven inflation of the type occurring naturally in string...

Metric Perturbations in Dilaton-Driven Inflation (1995)

Brustein, R., Gasperini, M., Giovannini, M., Mukhanov, V. F., Veneziano, G.

We compute the spectrum of scalar and tensor metric perturbations generated, as amplified vacuum fluctuations, during an epoch of dilaton-driven inflation of the type occurring naturally in string...

Homogeneous Conformal String Backgrounds (1995)

Gasperini, M., Ricci, R.

We present exact solutions characterised by Bianchi-type I,II,III,V,VI four-dimensional metric, space-independent dilaton, and vanishing torsion background, for the low energy string effective action...

Von Neumann and Shannon-Wehrl Entropy for Squeezed States and Cosmological Particle Production (1995)

M. Gasperini, M. Gasperini, M. Giovannini, M. Giovannini

We show that the effective coarse graining of a two-mode squeezed density matrix, implicit in the Wehrl approaches to a semiclassical phase-space distribution, leads to results in agreement with...

Amplification Of Vacuum Fluctuations In String Cosmology Backgrounds (1995)

Metric Perturbations in Dilaton-Driven Inflation (1995)

Inflationary string cosmology backgrounds can amplify perturbations in a more efficient way than conventional inflationary backgrounds, because the perturbation amplitude may grow - instead of being...

Brustein Gasperini, R. Brustein, M. Gasperini, M. Giovannini, V. F. Mukhanov, G. Veneziano

We compute the spectrum of scalar and tensor metric perturbations generated, as amplified vacuum fluctuations, during an epoch of dilaton-driven inflation of the type occurring naturally in string...

Electromagnetic Origin of the CMB Anisotropy in String Cosmology (1995)

Gasperini Dipartimento, M. Gasperini, M. Giovannini, G. Veneziano

In the inflationary scenarios suggested by string theory, the vacuum fluctuations of the electromagnetic field can be amplified by the time-evolution of the dilaton background, and can grow large...

Metric Perturbations in Dilaton-Driven Inflation (1995)

R. Brustein, M. Gasperini, M. Giovannini, V. F. Mukhanov, G. Veneziano

We compute the spectrum of scalar and tensor metric perturbations generated, as amplified vacuum fluctuations, during an epoch of dilaton-driven inflation of the type occurring naturally in string...

Von Neumann and Shannon-Wehrl Entropy for Squeezed States and Cosmological Particle Production (1995)

Von Neumann, Shannon-wehrl Entropy, M. Gasperini, M. Gasperini, M. Giovannini, M. Giovannini

We show that the e#ective coarse graining of a two-mode squeezed density matrix, implicit in the Wehrl approaches to a semiclassical phase-space distribution, leads to results in agreement with...

CERN-TH/95-85 DFTT-26/95 April 1995 Primordial Magnetic Fields (1995)

From String Cosmology, M. Gasperini, M. Giovannini, G. Veneziano

Su#ciently large seeds for generating the observed (inter)galactic magnetic fields emerge naturally in string cosmology from the amplification of electromagnetic vacuum fluctuations due to a...

Status of String Cosmology: Phenomenological Aspects (1995)

A simple P-wave polarization analysis: its application to earthquake location (1994)

I report recent studies on the evolution of perturbations in the context of the "pre-big-bang" scenario typical of string cosmology, with emphasis on the formation of a stochastic...

Alessandrini, B., Cattaneo, M., Demartin, M., Gasperini, M., Lanza, V.

We present a method for hypocentral location which takes into account all three components of ground motion and not only the vertical one, as it is usually done by standard least-square techniques...

A simple P-wave polarization analysis: its application to earthquake location (1994)

Alessandrini, B.; Istituto Nazionale Di Geofisica, Roma, Italy, Cattaneo, M.; Dister, Sezione Geofisica, Università Di Genova, Italy, Demartin, M.; C.N.R., Istituto Di Ricerca Sul Rischio Sismico, Milano, Italy, Gasperini, M.; C.N.R., Istituto Di Geologia Marina, Bologna, Italy, Lanza, V.; Dister, Sezione Geofisica, Università Di Genova, Italy

We present a method for hypocentral location which takes into account all three components of ground motion and not only the vertical one, as it is usually done by standard least-square techniques...

The Inflationary Role of the Dilaton in String Cosmology (1994)

Phenomenological Aspects of the Pre-Big-Bang Scenario in String Cosmology (1994)

It is stressed that the kinematical problems of the standard cosmological model can be solved by a phase of accelerated contraction of the cosmic scale factor. Such a behaviour is only a particular...

Dilaton production in string cosmology (1994)

I review various aspects of the pre-big-bang scenario and of its main open problems, with emphasis on the role played by the dilaton. Since the dilaton is a compelling consequence of string theory,...

Dilaton Production in String Cosmology (1994)

We consider the coupled evolution of density, (scalar) metric and dilaton perturbations in the transition from a "stringy" phase of growing curvature and gravitational coupling to the standard...

Relaxed Bounds on the Dilaton Mass in a String Cosmology Scenario (1994)

We consider the coupled evolution of density, (scalar) metric and dilaton perturbations in the transition from a ``stringy" phase of growing curvature and gravitational coupling to the standard...

Foreland tectonics in the southern Adriatic Sea (1994)

We discuss bounds on the dilaton mass, following from the cosmological amplification of the quantum fluctuations of the dilaton background, under the assumption that such fluctuations are dominant...

Argnani, A.; Ist. Geologia Marina, CNR, Bologna, Italia, Bortoluzzi, G.; Ist. Geologia Marina, CNR, Bologna, Italia, Favali, P.; Istituto Nazionale Di Geofisica E Vulcanologia, Sezione Roma2, Roma, Italia, Frugoni, F.; Istituto Nazionale Di Geofisica E Vulcanologia, Sezione Roma2, Roma, Italia, Gasperini, M.; Ist. Geologia Marina, CNR, Bologna, Italia, Ligi, M.; Ist. Geologia Marina, CNR, Bologna, Italia, ...

Two major deformation belts occur in the portion of the Adriatic Sea offshore the Gargano Promontory. The NE-SW - trending Tremiti Deformation Belt, located north of the Gargano Promontory,...

(b) (1994)

M. Gasperini, R. Ricci

We present exact solutions characterised by Bianchi-type I, II, III, V, VI 0, VI h four-dimensional metric, space-independent dilaton, and vanishing torsion background, for the low energy string...

Dilaton Production in String Cosmology (1994)

Dilaton Production in String Cosmology (1994)

We consider the coupled evolution of density, (scalar) metric and dilaton perturbations in the transition from a "stringy" phase of growing curvature and gravitational coupling to the...

Relaxed Bounds on the Dilaton Mass in a String Cosmology Scenario (1994)

We consider the coupled evolution of density, (scalar) metric and dilaton perturbations in the transition from a "stringy" phase of growing curvature and gravitational coupling to the...

Dftt-02/95 Rom2f/94/36 Homogeneous Conformal String Backgrounds (1994)

We discuss bounds on the dilaton mass, following from the cosmological amplification of the quantum fluctuations of the dilaton background, under the assumption that such fluctuations are dominant...

Gasperini And Ricci, M. Gasperini, R. Ricci

We present exact solutions characterised by Bianchi-type I, II, III, V, VI 0 , VI h four-dimensional metric, space-independent dilaton, and vanishing torsion background, for the low energy string...

A problem with non-Abelian duality? (1993)

Gasperini, M, Ricci, R A, Veneziano, Gabriele

Inflation Deflation and Frame-Independence in String Cosmology (1993)

Gasperini, M, Veneziano, G

The inflationary scenarios suggested by the duality properties of string cosmology in the Brans-Dicke (or String) frame are shown to correspond to accelerated contraction (deflation) when...

Inflation, deflation, and frame-independence in string cosmology (1993)

Quantum squeezing and cosmological entropy production (1993)

Gasperini, M, Giovannini, Massimo

The entropy growth in a cosmological process of pair production is completely determined by the associated squeezing parameter, and is insensitive to the number of particles in the initial state. The...

Quantum Squeezing and Cosmological Entropy Production (1993)

Squeezed thermal vacuum and the maximum scale for inflation (1993)

The entropy growth in a cosmological process of pair production is completely determined by the associated squeezing parameter, and is insensitive to the number of particles in the initial state. The...

Gasperini, M, Giovannini, Massimo, Veneziano, Gabriele

We consider the stimulated emission of gravitons from an initial state of thermal equilibrium, under the action of the cosmic gravitational background field. We find that the low-energy graviton...

Squeezed Thermal Vacuum and the Maximum Scale for Inflation (1993)

Entropy Production in the Cosmological Amplification of the Vacuum Fluctuations (1993)

We consider the stimulated emission of gravitons from an initial state of thermal equilibrium, under the action of the cosmic gravitational background field. We find that the low-energy graviton...

Foreland deformational pattern in the Southern Adriatic Sea (1993)

We estimate the entropy associated to a background of squeezed cosmic gravitons, and we argue that the process of cosmological pair production from the vacuum may explain the large amount of entropy...

Argnani, A.; Ist. Geologia Marina, CNR, Bologna, Italia, Favali, P.; Istituto Nazionale Di Geofisica E Vulcanologia, Sezione Roma1, Roma, Italia, Frugoni, F.; Istituto Nazionale Di Geofisica E Vulcanologia, Sezione Roma1, Roma, Italia, Gasperini, M.; Ist. Geologia Marina, CNR, Bologna, Italia, Ligi, M.; Ist. Geologia Marina, CNR, Bologna, Italia, Marani, M.; Ist. Geologia Marina, CNR, Bologna, Italia, ...

Two major deformation belts occur in the portion of the Adriatic Sea offshore the Gargano Promontory. Although these two belts display similar characters on seismic profiles, they are different in...

Foreland deformational pattern in the Southern Adriatic Sea (1993)

Argnani, A.; Istituto Per La Geologia Marina, CNR Bologna, Italia, Favalli, P.; Istituto Nazionale Di Geofisica E Vulcanologia, Sezione Roma1, Roma, Italia, Frugoni, F.; Istituto Nazionale Di Geofisica E Vulcanologia, Sezione Roma1, Roma, Italia, Gasperini, M.; Istituto Per La Geologia Marina, CNR Bologna, Italia, Ligi, M.; Istituto Per La Geologia Marina, CNR Bologna, Italia, Marani, M.; Istituto Per La Geologia Marina, CNR Bologna, Italia, ...

Squeezed Thermal Vacuum and the Maximum Scale for Inflation (1993)

M. Gasperini, M. Giovannini, G. Veneziano

We consider the stimulated emission of gravitons from an initial state of thermal equilibrium, under the action of the cosmic gravitational background field. We find that the low-energy graviton...

Inflation, Deflation, and Frame-Independence in String Cosmology (1993)

Quantum Squeezing and (1993)

The inflationary scenarios suggested by the duality properties of string cosmology in the Brans-Dicke (or String) frame are shown to correspond to accelerated contraction (deflation) when...

Cosmological Entropy Production, M. Gasperini, M. Giovannini

The entropy growth in a cosmological process of pair production is completely determined by the associated squeezing parameter, and is insensitive to the number of particles in the initial state. The...

CERN-TH.6955/93 Inflation, Deflation, and Frame-Independence in String Cosmology (1993)

Dilaton Contributions to the Cosmic Gravitational Wave Background (1992)

The inflationary scenarios suggested by the duality properties of string cosmology in the Brans-Dicke (or String) frame are shown to correspond to accelerated con-traction (deflation) when...

Pre-Big-Bang in String Cosmology (1992)

We consider the cosmological amplification of a metric perturbation propagating in a higher-dimensional Brans-Dicke background, including a non trivial dilaton evolution. We discuss the properties of...

Pre-big-bang in string cosmology (1992)

The duality-type symmetries of string cosmology naturally lead to a pre-big-bang phase of accelerated evolution as dual counterpart of the decelerated expansion of standard cosmology. We discuss...

Boosting away singularities from conformal string backgrounds (1992)

The duality-type symmetries of string cosmology naturally lead to a pre-big-bang phase of accelerated evolution as dual counterpart of the decelerated expansion of standard cosmology. We discuss...

Gasperini, M, Maharana, J, Veneziano, Gabriele

Generalizing our previous work, we show how $O(d,d)$ transformations can be used to "boost away" in new dimensions the physical singularities that occur generically in cosmological and/or black-hole...

Boosting Away Singularities from Conformal String Backgrounds (1992)

Gasperini, M., Maharana, J., Veneziano, G.

Generalizing our previous work, we show how $O(d,d)$ transformations can be used to "boost away" in new dimensions the physical singularities that occur generically in cosmological and/or black-hole...

Pre-Big-Bang in String Cosmology (1992)

M. Gasperini, G. Veneziano, Istituto Nazionale, Fisica Nucleare, Sezione Di Torino

The duality-type symmetries of string cosmology naturally lead us to expect a pre-big-bang phase of accelerated evolution as the dual counterpart of the decelerating expansion era of standard...

Boosting Away Singularities From Conformal String Backgrounds (1992)

Inflation in Scalar-Tensor Gravity with Quadratic Gauss-Bonnet Self-Interactions (1992)

Generalizing our previous work, we show how O(d; d) transformations can be used to "boost away" in new dimensions the physical singularities that occur generically in cosmological and/or...

Pre-Big-Bang in String Cosmology (1992)

We present cosmological solutions for a graviton-plus-dilaton system coupled to a perfect fluid source, including quadratic curvature corrections .We show that, even in the absence of a dilaton...

M. Gasperini, G. Veneziano, Istituto Nazionale, Fisica Nucleare, Sezione Di Torino

The duality-type symmetries of string cosmology naturally lead us to expect a pre-big-bang phase of accelerated evolution as the dual counterpart of the decelerating expansion era of standard...

Boosting Away Singularities From Conformal String Backgrounds (1992)

Dilaton Contributions To The Cosmic Gravitational Wave Background (1992)

Generalizing our previous work, we show how O(d, d) transformations can be used to "boost away" in new dimensions the physical singularities that occur generically in cosmological and/or...

Entropy Production in the Cosmological Amplification of the Vacuum Fluctuations (1992)

We consider the cosmological amplification of a metric perturbation propagating in a higher-dimensional Brans-Dicke background, including a non trivial dilaton evolution. We discuss the properties of...

Gravity Waves from Primordial Dimensional Reduction (1992)

We estimate the entropy associated to a background of squeezed cosmic gravitons, and we argue that the process of cosmological pair production from the vacuum may explain the large amount of entropy...

Constraints on Inflation at the Planck Scale from the Relic Graviton Spectrum (1992)

We show that the dynamical contraction of n "internal" spacelike dimensions leads, in general, to the formation of a cosmic graviton background, similar to that produced by inflation. By...

$O(d,d)$-Covariant String Cosmology (1991)

Constraints on the maximum allowed scale for de Sitter inflation can be evaded if the de Sitter phase is preceded by an epoch of growing curvature and accelerated expansion (superinflation). In this...

O(d,d)-covariant string cosmology (1991)

The recently discovered $O(d,d)$ symmetry of the space of slowly varying cosmological string vacua in $d+1$ dimensions is shown to be preserved in the presence of bulk string matter. The existence of...

From trivial to non-trivial conformal string backgrounds via O(d,d) transformations (1991)

Gasperini, M, Maharana, J P, Veneziano, Gabriele

Self-sustained inflation and dimensional reduction from fundamental strings (1991)

Gasperini, M, Sánchez, N, Veneziano, Gabriele

O(d,d)-Covariant String Cosmology (1991)

FROM TRIVIAL TO NON-TRIVIAL CONFORMAL STRING BACKGROUNDS VIA O(d,d) TRANSFORMATIONS (1991)

The recently discovered O(d; d) symmetry of the space of (slowly-varying) cosmological string vacua in d + 1 dimensions is shown to be preserved in the presence of bulk string matter. The existence...

M. Gasperini, J. MAHARANA, G. VENEZIANO, Sezione Di Torino

Recently proposed extensions of target-space duality and Narain transformations can be used to generate highly non-trivial conformal string backgrounds out of (almost) trivial ones. The example of...

Self-Sustained Inflation And Dimensional Reduction From Fundamental Strings (1991)

M. Gasperini, N. Sanchez, G. Veneziano

In a previous paper we have shown that an ideal gas of fundamental strings is not able to sustain, by itself, a phase of isotropic inflation of the Universe. We show here that fundamental strings can...

Inflation in scalar-tensor gravity with quadratic Gauss-Bonnet self-interactions (1991)

A Geometric Regularization Procedure For The Curvature Of Cosmological Backgrounds (1991)

We present cosmological solutions for a graviton-plus-dilaton system coupled to a perfect fluid source, including quadratic curvature corrections. We show that, even in the absence of a dilaton...

Causal Horizons, Accelerations and Strings (1991)

A formal procedure is presented, which can regularize a given cosmological metric by avoiding the occurrence of curvatures and densities larger than the Planck ones. The method is applied, in...

North-Holland PHYSICS LETTERS B From trivial to non-trivial conformal string backgrounds via O (d, d) transformations (1991)

All the points of a string are always causally connected provided their relative acceleration is smaller than the critical value a c = (mff 0 ) \Gamma1 , where m is the mass and 1=ff 0 the string...

O(d,d)-Covariant String Cosmology (1991)

Recently proposed extensions of target-space duality and Narain transformations can be used to generate highly non-trivial conformal string backgrounds out of (almost) trivial ones. The example...

Highly unstable fundamental strings in inflationary cosmologies (1990)

The recently discovered O(d; d) symmetry of the space of (slowly-varying) cosmological string vacua in d + 1 dimensions is shown to be preserved in the presence of bulk string matter. The existence...

Gasperini, M, Sánchez, N, Veneziano, Gabriele

in a background gravitational field (1990)