Vincenzo Branchina - Academia.edu (original) (raw)

Papers by Vincenzo Branchina

Cornell University - arXiv, Apr 28, 2016

Assuming that the short gamma-ray burst detected by the Fermi Gamma-Ray Space Telescope about 0.4... more Assuming that the short gamma-ray burst detected by the Fermi Gamma-Ray Space Telescope about 0.4 seconds after the gravitational waves observed by the LIGO and VIRGO Collaborations originated from the same black hole merger event, we perform a model-independent analysis of different quantum gravity scenarios based on (modified) dispersion relations (typical of quantum gravity models) for the graviton and the photon. We find that only scenarios where at least one of the two particles is luminal (the other being sub-or super-luminal) are allowed, while scenarios where none of the two particles is luminal are ruled out. Moreover, the physical request of having acceptable values for the quantum gravity scale imposes stringent bounds on the difference between the velocities of electromagnetic and gravitational waves, much more stringent than any previously known bound.

Physical Review D

While it is usually stated that dimensional regularization (DR) has no direct physical interpreta... more While it is usually stated that dimensional regularization (DR) has no direct physical interpretation, consensus has recently grown on the idea that it might be endowed with special physical properties that would provide the mechanism that solves the naturalness/hierarchy problem. Comparing direct Wilsonian calculations with the corresponding DR ones, we find that DR indeed has a well-defined physical meaning, and we point out its limitations. In particular, our results show that DR cannot provide the solution to the naturalness/hierarchy problem. The absence of too large corrections to the Higgs boson mass is due to a secretly realized fine-tuning, rather than special physical properties of DR. We also investigate these issues within the Wilsonian RG framework and, by comparison with the usual perturbative RG analysis, we show that several popular proposals for the resolution of the problem, commonly considered as physical mechanisms free of fine-tuning, again secretly implement the tuning.

Cornell University - arXiv, Sep 24, 2020

A formal expansion for the Green's functions of an interacting quantum field theory in a paramete... more A formal expansion for the Green's functions of an interacting quantum field theory in a parameter that somehow encodes its "distance" from the corresponding non-interacting one was introduced more than thirty years ago, and has been recently reconsidered in connection with its possible application to the renormalization of non-hermitian theories. Besides this new and interesting application, this expansion has special properties already when applied to ordinary (i.e. hermitian) theories, and in order to disentangle the peculiarities of the expansion itself from those of non-hermitian theories, it is worth to push further the investigation limiting first the analysis to ordinary theories. In the present work we study some aspects related to the renormalization of a scalar theory within the framework of such an expansion. Due to its peculiar properties, it turns out that at any finite order in the expansion parameter the theory looks as non-interacting. We show that when diagrams of appropriate classes are resummed, this apparent drawback disappears and the theory recovers its interacting character. In particular we have seen that with a certain class of diagrams, the weak-coupling expansion results are recovered, thus establishing a bridge between the two expansions.

We carefully analyse the use of the effective action in dynamical problems, in particular the con... more We carefully analyse the use of the effective action in dynamical problems, in particular the conditions under which the equation δΓ = 0 can be used as a δφ quantum equation of motion, and the relation between the asymptotic states involved in the definition of Γ and the initial state of the system. By considering the quantum mechanical example of a double-well potential, where we can get exact results for the time evolution of the system, we show that an approximation to the effective potential in the quantum equation of motion that correctly describes the dynamical evolution of the system is obtained with the help of the wilsonian RG equation (already at the lowest order of the derivative expansion), while the commonly used one-loop effective potential fails to reproduce the exact results.

Physical Review D, 2019

The Higgs effective potential becomes unstable at approximately 10 11 GeV, and if only standard m... more The Higgs effective potential becomes unstable at approximately 10 11 GeV, and if only standard model interactions are considered, the lifetime τ of the electroweak vacuum turns out to be much larger than the age of the Universe TU. It is well known, however, that τ is extremely sensitive to the presence of unknown new physics: the latter can enormously lower τ. This poses a serious problem for the stability of our Universe, demanding for a physical mechanism that protects it from a disastrous decay. We have found that there exists a universal stabilizing mechanism that naturally originates from the nonminimal coupling between gravity and the Higgs boson. As this Higgs-gravity interaction necessarily arises from the quantum dynamics of the Higgs field in a gravitational background, this stabilizing mechanism is certainly present. It is not related to any specific model, being rather natural and universal as it comes from fundamental pillars of our physical world: gravity, the Higgs field, the quantum nature of physical laws.

A detailed study of aPT -symmetric zero-dimensional quartic theory is presented and a comparison ... more A detailed study of aPT -symmetric zero-dimensional quartic theory is presented and a comparison between the properties of this theory and those of a conventional quartic theory is given. It is shown that thePT -symmetric quartic theory evades the consequences of the Mermin-Wagner-Coleman theorem regarding the absence of symmetry breaking in d < 2 dimensions. Furthermore, the PT -symmetric theory does not satisfy the usual Bogoliubov limit for the construction of the Green’s functions because one obtains dierent results for the h! 0 and the h! 0 + limits.

EPL (Europhysics Letters), 2017

The knowledge of the stability condition of the electroweak (EW) vacuum is of the greatest import... more The knowledge of the stability condition of the electroweak (EW) vacuum is of the greatest importance for our understanding of beyond Standard Model (BSM) physics. It is widely believed that new physics that lives at very high energy scales should have no impact on the stability analysis. This expectation has been recently challenged, but the results were controversial as new physics was given in terms of non-renormalizable higher order operators. Here we consider for the first time a renormalizable (toy) UV completion of the SM, and definitely show that such a decoupling does not take place. This result has important phenomenological consequences, providing a very useful test for BSM theories. In particular, it shows that speculations based on the so called "criticality" do not appear to be well founded.

EPL (Europhysics Letters), 2016

In a pioneering paper on the role of gravity on false vacuum decay, Coleman and De Luccia showed ... more In a pioneering paper on the role of gravity on false vacuum decay, Coleman and De Luccia showed that a strong gravitational field can stabilize the false vacuum, suppressing the formation of true vacuum bubbles. This result is obtained for the case when the energy density difference between the two vacua is small, the so called thin wall regime, but is considered of more general validity. Here we show that when this condition does not hold, however, a strong gravitational field (Planckian physics) does not necessarily induce a total suppression of true vacuum bubble nucleation. Contrary to common expectations then, gravitational physics at the Planck scale does not stabilize the false vacuum. These results are of crucial importance for the stability analysis of the electroweak vacuum and for searches of new physics beyond the Standard Model.

A detailed study of a PT-symmetric zero-dimensional quartic theory is presented and a comparison ... more A detailed study of a PT-symmetric zero-dimensional quartic theory is presented and a comparison between the properties of this theory and those of a conventional quartic theory is given. It is shown that the PT-symmetric quartic theory evades the consequences of the Mermin-Wagner-Coleman theorem regarding the absence of symmetry breaking in d<2 dimensions. Furthermore, the PT-symmetric theory does not satisfy the usual Bogoliubov limit for the construction of the Green's functions because one obtains different results for the hto0−h\to0^-hto0− and the hto0+h\to0^+hto0+ limits.

Physical Review D, 2015

If the Standard Model (SM) is valid up to extremely high energy scales, then the Higgs potential ... more If the Standard Model (SM) is valid up to extremely high energy scales, then the Higgs potential becomes unstable at approximately 10 11 GeV. However, calculations of the lifetime of the SM vacuum have shown that it vastly exceeds the age of the Universe. It was pointed out by two of us (VB,EM) that these calculations are extremely sensitive to effects from Planck scale higher-dimensional operators and, without knowledge of these operators, firm conclusions about the lifetime of the SM vacuum cannot be drawn. The previous paper used analytical approximations to the potential and, except for Higgs contributions, ignored loop corrections to the bounce action. In this work, we do not rely on any analytical approximations and consider all contributions to the bounce action, confirming the earlier result. It is surprising that the Planck scale operators can have such a large effect when the instability is at 10 11 GeV. There are two reasons for the size of this effect. In typical tunneling calculations, the value of the field at the center of the critical bubble is much larger than the point of the instability; in the SM case, this turns out to be numerically within an order of magnitude of the Planck scale. In addition, tunneling is an inherently non-perturbative phenomenon, and may not be as strongly suppressed by inverse powers of the Planck scale. We include effective Φ 6 and Φ 8 Planck-scale operators and show that they can have an enormous effect on the tunneling rate.

We introduce a scale-dependent effective action defined through a partial Legendre transform firs... more We introduce a scale-dependent effective action defined through a partial Legendre transform first discussed by Zumino more than 30 years ago. This new effective action depends, at any scale, on all degrees of freedom, is gauge-invariant/general-covariant, and obeys a simple, exact and manifestly gauge-invariant RG-flow equation. It should be useful in a variety of problems, including some pertaining to non-abelian gauge theories and quantum gravity.

The renormalization group is applied to the phi4 model in the symmetry broken phase in order to i... more The renormalization group is applied to the phi4 model in the symmetry broken phase in order to identify different scaling regimes. The new scaling laws reflect nonuniversal behavior at the phase transition. The extension of the analysis to finite temperature is briefly outlined. It is mentioned that the coupling constants can be found in the mixed phase by taking into

Journal of High Energy Physics, 2014

The possibility that new physics beyond the Standard Model (SM) appears only at the Planck scale ... more The possibility that new physics beyond the Standard Model (SM) appears only at the Planck scale M P is often considered. However, it is usually assumed that new physics interactions at M P do not affect the electroweak vacuum lifetime, so the latter is obtained neglecting these terms. According to the resulting stability phase diagram, for the current experimental values of the top and Higgs masses, our universe lives in a metastable state (with very long lifetime), near the edge of stability. However, we show that the stability phase diagram strongly depends on new physics and that, despite claims to the contrary, a more precise determination of the top (as well as of the Higgs) mass will not allow to discriminate between stability, metastability or criticality of the electroweak vacuum. At the same time, we show that the conditions needed for the realization of Higgs inflation scenarios (all obtained neglecting new physics) are too sensitive to the presence of new interactions at M P. Therefore, Higgs inflation scenarios require very severe fine tunings that cast serious doubts on these models.

Physical Review D, 1990

The convexity property of the variational approximations to the effective potential is analyzed b... more The convexity property of the variational approximations to the effective potential is analyzed both in quantum mechanics and in A, P field theory. A simple calculational scheme, based on the generalization of the Gaussian functionals subspace, allows one to reproduce this fundamental feature of the exact effective potential to a very high degree of accuracy. A criterion to clarify the occurrence of spontaneous symmetry breaking in the presence of a flat effective potential is proposed.

Physics Letters B, 2002

Chiral symmetry breaking in a purely fermionic theory is investigated by the help of the renormal... more Chiral symmetry breaking in a purely fermionic theory is investigated by the help of the renormalization group method. The RG equation for the running mass m k admits a solution with vanishing bare mass and finite physical mass. The running Fermi coupling constant, G k , converges to a finite (renormalized) physical value. It is also shown that the RG equation forG, the dimensionless Fermi coupling, has an UV fixed pointG U V. Contrary to a previous result however, it is proven that the chiral symmetry breaking point G c does not coincide withG U V .

Physics Letters B, 2003

We combine old ideas about exact renormalization-group-flow (RGF) equations with the Vilkovisky-D... more We combine old ideas about exact renormalization-group-flow (RGF) equations with the Vilkovisky-De Witt (VDW) approach to reparametrization invariant effective actions and arrive at a new, exact, gauge-invariant RGF equation. The price to be paid for such a result is that both the action and the RGF equation depend explicitly upon the base point (in field space) needed for the VDW construction. We briefly discuss the complications originating from this fact and possible ways to overcome them.

Physical Review Letters, 2002

Physical Review Letters, 2013

Assuming that the particle with mass ∼ 126 GeV discovered at LHC is the Standard Model Higgs boso... more Assuming that the particle with mass ∼ 126 GeV discovered at LHC is the Standard Model Higgs boson, we find that the stability of the EW vacuum strongly depends on new physics interaction at the Planck scale MP , despite of the fact that they are higher-dimensional interactions, apparently suppressed by inverse powers of MP. In particular, for the present experimental values of the top and Higgs masses, if τ is the lifetime of the EW vacuum, new physics can turn τ from τ >> TU to τ << TU , where TU is the age of the Universe, thus weakening the conclusions of the so called meta-stability scenario.

Physical Review D, 2004

We carefully analyse the contribution to the oscillations of a metallic gravitational antenna due... more We carefully analyse the contribution to the oscillations of a metallic gravitational antenna due to the interaction between the electrons of the bar and the incoming gravitational wave. To this end, we first derive the total microscopic Hamiltonian of the wave-antenna system and then compute the contribution to the attenuation factor due to the electron-graviton interaction. As compared to the ordinary damping factor, which is due to the electron viscosity, this term turns out to be totally negligible. This result confirms that the only relevant mechanism for the interaction of a gravitational wave with a metallic antenna is its direct coupling with the bar normal modes.

Cornell University - arXiv, Apr 28, 2016

Assuming that the short gamma-ray burst detected by the Fermi Gamma-Ray Space Telescope about 0.4... more Assuming that the short gamma-ray burst detected by the Fermi Gamma-Ray Space Telescope about 0.4 seconds after the gravitational waves observed by the LIGO and VIRGO Collaborations originated from the same black hole merger event, we perform a model-independent analysis of different quantum gravity scenarios based on (modified) dispersion relations (typical of quantum gravity models) for the graviton and the photon. We find that only scenarios where at least one of the two particles is luminal (the other being sub-or super-luminal) are allowed, while scenarios where none of the two particles is luminal are ruled out. Moreover, the physical request of having acceptable values for the quantum gravity scale imposes stringent bounds on the difference between the velocities of electromagnetic and gravitational waves, much more stringent than any previously known bound.

Physical Review D

While it is usually stated that dimensional regularization (DR) has no direct physical interpreta... more While it is usually stated that dimensional regularization (DR) has no direct physical interpretation, consensus has recently grown on the idea that it might be endowed with special physical properties that would provide the mechanism that solves the naturalness/hierarchy problem. Comparing direct Wilsonian calculations with the corresponding DR ones, we find that DR indeed has a well-defined physical meaning, and we point out its limitations. In particular, our results show that DR cannot provide the solution to the naturalness/hierarchy problem. The absence of too large corrections to the Higgs boson mass is due to a secretly realized fine-tuning, rather than special physical properties of DR. We also investigate these issues within the Wilsonian RG framework and, by comparison with the usual perturbative RG analysis, we show that several popular proposals for the resolution of the problem, commonly considered as physical mechanisms free of fine-tuning, again secretly implement the tuning.

Cornell University - arXiv, Sep 24, 2020

A formal expansion for the Green's functions of an interacting quantum field theory in a paramete... more A formal expansion for the Green's functions of an interacting quantum field theory in a parameter that somehow encodes its "distance" from the corresponding non-interacting one was introduced more than thirty years ago, and has been recently reconsidered in connection with its possible application to the renormalization of non-hermitian theories. Besides this new and interesting application, this expansion has special properties already when applied to ordinary (i.e. hermitian) theories, and in order to disentangle the peculiarities of the expansion itself from those of non-hermitian theories, it is worth to push further the investigation limiting first the analysis to ordinary theories. In the present work we study some aspects related to the renormalization of a scalar theory within the framework of such an expansion. Due to its peculiar properties, it turns out that at any finite order in the expansion parameter the theory looks as non-interacting. We show that when diagrams of appropriate classes are resummed, this apparent drawback disappears and the theory recovers its interacting character. In particular we have seen that with a certain class of diagrams, the weak-coupling expansion results are recovered, thus establishing a bridge between the two expansions.

We carefully analyse the use of the effective action in dynamical problems, in particular the con... more We carefully analyse the use of the effective action in dynamical problems, in particular the conditions under which the equation δΓ = 0 can be used as a δφ quantum equation of motion, and the relation between the asymptotic states involved in the definition of Γ and the initial state of the system. By considering the quantum mechanical example of a double-well potential, where we can get exact results for the time evolution of the system, we show that an approximation to the effective potential in the quantum equation of motion that correctly describes the dynamical evolution of the system is obtained with the help of the wilsonian RG equation (already at the lowest order of the derivative expansion), while the commonly used one-loop effective potential fails to reproduce the exact results.

Physical Review D, 2019

The Higgs effective potential becomes unstable at approximately 10 11 GeV, and if only standard m... more The Higgs effective potential becomes unstable at approximately 10 11 GeV, and if only standard model interactions are considered, the lifetime τ of the electroweak vacuum turns out to be much larger than the age of the Universe TU. It is well known, however, that τ is extremely sensitive to the presence of unknown new physics: the latter can enormously lower τ. This poses a serious problem for the stability of our Universe, demanding for a physical mechanism that protects it from a disastrous decay. We have found that there exists a universal stabilizing mechanism that naturally originates from the nonminimal coupling between gravity and the Higgs boson. As this Higgs-gravity interaction necessarily arises from the quantum dynamics of the Higgs field in a gravitational background, this stabilizing mechanism is certainly present. It is not related to any specific model, being rather natural and universal as it comes from fundamental pillars of our physical world: gravity, the Higgs field, the quantum nature of physical laws.

A detailed study of aPT -symmetric zero-dimensional quartic theory is presented and a comparison ... more A detailed study of aPT -symmetric zero-dimensional quartic theory is presented and a comparison between the properties of this theory and those of a conventional quartic theory is given. It is shown that thePT -symmetric quartic theory evades the consequences of the Mermin-Wagner-Coleman theorem regarding the absence of symmetry breaking in d < 2 dimensions. Furthermore, the PT -symmetric theory does not satisfy the usual Bogoliubov limit for the construction of the Green’s functions because one obtains dierent results for the h! 0 and the h! 0 + limits.

EPL (Europhysics Letters), 2017

The knowledge of the stability condition of the electroweak (EW) vacuum is of the greatest import... more The knowledge of the stability condition of the electroweak (EW) vacuum is of the greatest importance for our understanding of beyond Standard Model (BSM) physics. It is widely believed that new physics that lives at very high energy scales should have no impact on the stability analysis. This expectation has been recently challenged, but the results were controversial as new physics was given in terms of non-renormalizable higher order operators. Here we consider for the first time a renormalizable (toy) UV completion of the SM, and definitely show that such a decoupling does not take place. This result has important phenomenological consequences, providing a very useful test for BSM theories. In particular, it shows that speculations based on the so called "criticality" do not appear to be well founded.

EPL (Europhysics Letters), 2016

In a pioneering paper on the role of gravity on false vacuum decay, Coleman and De Luccia showed ... more In a pioneering paper on the role of gravity on false vacuum decay, Coleman and De Luccia showed that a strong gravitational field can stabilize the false vacuum, suppressing the formation of true vacuum bubbles. This result is obtained for the case when the energy density difference between the two vacua is small, the so called thin wall regime, but is considered of more general validity. Here we show that when this condition does not hold, however, a strong gravitational field (Planckian physics) does not necessarily induce a total suppression of true vacuum bubble nucleation. Contrary to common expectations then, gravitational physics at the Planck scale does not stabilize the false vacuum. These results are of crucial importance for the stability analysis of the electroweak vacuum and for searches of new physics beyond the Standard Model.

A detailed study of a PT-symmetric zero-dimensional quartic theory is presented and a comparison ... more A detailed study of a PT-symmetric zero-dimensional quartic theory is presented and a comparison between the properties of this theory and those of a conventional quartic theory is given. It is shown that the PT-symmetric quartic theory evades the consequences of the Mermin-Wagner-Coleman theorem regarding the absence of symmetry breaking in d<2 dimensions. Furthermore, the PT-symmetric theory does not satisfy the usual Bogoliubov limit for the construction of the Green's functions because one obtains different results for the hto0−h\to0^-hto0− and the hto0+h\to0^+hto0+ limits.

Physical Review D, 2015

If the Standard Model (SM) is valid up to extremely high energy scales, then the Higgs potential ... more If the Standard Model (SM) is valid up to extremely high energy scales, then the Higgs potential becomes unstable at approximately 10 11 GeV. However, calculations of the lifetime of the SM vacuum have shown that it vastly exceeds the age of the Universe. It was pointed out by two of us (VB,EM) that these calculations are extremely sensitive to effects from Planck scale higher-dimensional operators and, without knowledge of these operators, firm conclusions about the lifetime of the SM vacuum cannot be drawn. The previous paper used analytical approximations to the potential and, except for Higgs contributions, ignored loop corrections to the bounce action. In this work, we do not rely on any analytical approximations and consider all contributions to the bounce action, confirming the earlier result. It is surprising that the Planck scale operators can have such a large effect when the instability is at 10 11 GeV. There are two reasons for the size of this effect. In typical tunneling calculations, the value of the field at the center of the critical bubble is much larger than the point of the instability; in the SM case, this turns out to be numerically within an order of magnitude of the Planck scale. In addition, tunneling is an inherently non-perturbative phenomenon, and may not be as strongly suppressed by inverse powers of the Planck scale. We include effective Φ 6 and Φ 8 Planck-scale operators and show that they can have an enormous effect on the tunneling rate.

We introduce a scale-dependent effective action defined through a partial Legendre transform firs... more We introduce a scale-dependent effective action defined through a partial Legendre transform first discussed by Zumino more than 30 years ago. This new effective action depends, at any scale, on all degrees of freedom, is gauge-invariant/general-covariant, and obeys a simple, exact and manifestly gauge-invariant RG-flow equation. It should be useful in a variety of problems, including some pertaining to non-abelian gauge theories and quantum gravity.

The renormalization group is applied to the phi4 model in the symmetry broken phase in order to i... more The renormalization group is applied to the phi4 model in the symmetry broken phase in order to identify different scaling regimes. The new scaling laws reflect nonuniversal behavior at the phase transition. The extension of the analysis to finite temperature is briefly outlined. It is mentioned that the coupling constants can be found in the mixed phase by taking into

Journal of High Energy Physics, 2014

The possibility that new physics beyond the Standard Model (SM) appears only at the Planck scale ... more The possibility that new physics beyond the Standard Model (SM) appears only at the Planck scale M P is often considered. However, it is usually assumed that new physics interactions at M P do not affect the electroweak vacuum lifetime, so the latter is obtained neglecting these terms. According to the resulting stability phase diagram, for the current experimental values of the top and Higgs masses, our universe lives in a metastable state (with very long lifetime), near the edge of stability. However, we show that the stability phase diagram strongly depends on new physics and that, despite claims to the contrary, a more precise determination of the top (as well as of the Higgs) mass will not allow to discriminate between stability, metastability or criticality of the electroweak vacuum. At the same time, we show that the conditions needed for the realization of Higgs inflation scenarios (all obtained neglecting new physics) are too sensitive to the presence of new interactions at M P. Therefore, Higgs inflation scenarios require very severe fine tunings that cast serious doubts on these models.

Physical Review D, 1990

The convexity property of the variational approximations to the effective potential is analyzed b... more The convexity property of the variational approximations to the effective potential is analyzed both in quantum mechanics and in A, P field theory. A simple calculational scheme, based on the generalization of the Gaussian functionals subspace, allows one to reproduce this fundamental feature of the exact effective potential to a very high degree of accuracy. A criterion to clarify the occurrence of spontaneous symmetry breaking in the presence of a flat effective potential is proposed.

Physics Letters B, 2002

Chiral symmetry breaking in a purely fermionic theory is investigated by the help of the renormal... more Chiral symmetry breaking in a purely fermionic theory is investigated by the help of the renormalization group method. The RG equation for the running mass m k admits a solution with vanishing bare mass and finite physical mass. The running Fermi coupling constant, G k , converges to a finite (renormalized) physical value. It is also shown that the RG equation forG, the dimensionless Fermi coupling, has an UV fixed pointG U V. Contrary to a previous result however, it is proven that the chiral symmetry breaking point G c does not coincide withG U V .

Physics Letters B, 2003

We combine old ideas about exact renormalization-group-flow (RGF) equations with the Vilkovisky-D... more We combine old ideas about exact renormalization-group-flow (RGF) equations with the Vilkovisky-De Witt (VDW) approach to reparametrization invariant effective actions and arrive at a new, exact, gauge-invariant RGF equation. The price to be paid for such a result is that both the action and the RGF equation depend explicitly upon the base point (in field space) needed for the VDW construction. We briefly discuss the complications originating from this fact and possible ways to overcome them.

Physical Review Letters, 2002

Physical Review Letters, 2013

Assuming that the particle with mass ∼ 126 GeV discovered at LHC is the Standard Model Higgs boso... more Assuming that the particle with mass ∼ 126 GeV discovered at LHC is the Standard Model Higgs boson, we find that the stability of the EW vacuum strongly depends on new physics interaction at the Planck scale MP , despite of the fact that they are higher-dimensional interactions, apparently suppressed by inverse powers of MP. In particular, for the present experimental values of the top and Higgs masses, if τ is the lifetime of the EW vacuum, new physics can turn τ from τ >> TU to τ << TU , where TU is the age of the Universe, thus weakening the conclusions of the so called meta-stability scenario.

Physical Review D, 2004

We carefully analyse the contribution to the oscillations of a metallic gravitational antenna due... more We carefully analyse the contribution to the oscillations of a metallic gravitational antenna due to the interaction between the electrons of the bar and the incoming gravitational wave. To this end, we first derive the total microscopic Hamiltonian of the wave-antenna system and then compute the contribution to the attenuation factor due to the electron-graviton interaction. As compared to the ordinary damping factor, which is due to the electron viscosity, this term turns out to be totally negligible. This result confirms that the only relevant mechanism for the interaction of a gravitational wave with a metallic antenna is its direct coupling with the bar normal modes.