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Search Results: 1 - 10 of 27450 matches for " Robert Brout "
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Of Inflation and the Inflaton
Robert Brout
Physics , 2010,
Abstract: Due to intra-field gravitational interactions, field configurations have a strong negative component to their energy density at the planckian and transplanckian scales, conceivably resulting in a sequestration of the transplanckian field degrees of freedom. Quantum fluctuations then allow these to tunnel into cisplanckian configurations to seed inflation and conventional observed physics: propagating modes of QFT in a geometry which responds to the existence of these new modes through the energy constraint of general relativity, H^2 = \rho/3. That this tunnelling results in geometries and field configurations that are homogeneous allows for an estimate of the mass of the inflaton, m=O(10^{-6}), and the amplitude of the inflaton condensate, \phiav=O(10), both consistent with phenomenology.
The Inflaton and its Mass
Robert Brout
Physics , 2002,
Abstract: In the context of the two fluid model of space-time fluctuations proposed to tame the transplanckian problem encountered in black hole physics, it is postulated that the inflaton is the fluctuation of mode density, ``the vapor component'' of the model. The mass of the inflaton is occasioned by the exchange of degrees of freedom between the ``vapor'' and the ``liquid'', the planckian ``soup'' in which usual ``cisplanckian'' fields propagate. This exchange between vacuum fluctuations is modeled after its counterpart in the real world i.e. black hole evaporation. In order of magnitude, a very rough semiquantitative estimate, would situate the mass somewhere between $10^{-10}$ and $10^{-5}$ planck masses, the largest uncertainty being the mass of the planckian black hole fluctuation i.e. the entropy that one ascribes to it.
A Brief Course in Spontaneous Symmetry Breaking I. The Paleolitic Age
Robert Brout
Physics , 2002,
Abstract: The physical world is marked by the phenomenon of spontaneous broken symmetry (SBS) i.e. where the state of a system is assymmetric with respect to the symmetry principles that govern its dynamics. For material systems this is not surprising since more often than not energetic considerations dictate that the ground state or low lying excited states of many body system become ordered i.e. a collective variable, such as magnetization or the Fourier transform of the density of a solid, picks up expectation values which otherwise would vanish by virtue of the dynamical symmetry(isotropy or translational symmetry in the aforementioned examples). More surprising was the discovery of the role of SBS in describing the vacuum or low lyng excitations of a quantum field theory. First came spontaneously broken chiral symmetry which was then applied to soft pion physics. When combined with current algebra, this field dominated particle physics in the 60's. Then came the application of the notion of SBS to situations where the symmetry is locally implemented by gauge fields. In that case the concept of order becomes more subtle. This development lead the way to electroweak unification and it remains one of the principal tools of the theorist in the quest for physics beyond the standard model. This brief review is intended to span the history of SBS with emphasis on conceptual rather than quantitative content. It is a written version of lectures of R.Brout on the ``Paleolithic Age'' and on ``Modern Times'' by F.Englert, i.e. respectively without and with gauge fields.
From Inflation to Dark Energy
Robert Brout
Physics , 2005,
Abstract: It is proposed that after the macroscopic fluctuation of energy density that is responsible for inflation dies away, a class of microscopic fluctuations, always present, survives to give the present day dark energy. This latter is simply a reinterpretation of the causet mechanism of Ahmed, Dodelson, Green and Sorkin, wherein the emergence of space is dropped but only energy considerations are maintained. At postinflation times, energy is exchanged between the "cisplanckian" cosmos and an unknown foam-like transplanckian reservoir. Whereas during inflation, the energy flows only from the latter to the former after inflation it fluctuates in sign thereby accounting for the tiny effective cosmological constant that seems to account for dark energy.
Notes on Connes' Construction of the Standard Model
Robert Brout
Physics , 1997, DOI: 10.1016/S0920-5632(97)00969-9
Abstract: The mathematical apparatus of non commutative geometry and operator algebras which Connes has brought to bear to construct a rational scheme for the internal symmetries of the standard model is presented from the physicist's point of view. Gauge symmetry, anomaly freedom, conservation of electric charge, parity violation and charge conjugation all play a vital role. When put together with a relatively simple set of algebraic algorithms they deliver many of the features of the standard model which otherwise seem rather ad hoc.
The Causet Mechanism for the Creation of Energy
Robert Brout
Physics , 2006,
Abstract: Sorkin's causet mechanism is generalized to include energy exchange between causet elements and conventional vacuum fluctuations to the inflationary epoch. In this, the dark energy of the adiabatic era is the fluctuating remnant of inflation. The mechanism is also applicable to black hole evaporation.
Condensation of Planckian Modes and the Inflaton
Robert Brout
Physics , 2003,
Abstract: To confront the transplanckian problem encountered in the backward extrapolation of the cosmological expansion of the momenta of the modes of quantum field theory, it is proposed that there is a reservoir, depository of transplanckian degrees of freedom. These are solicited by the cisplanckian modes so as to keep their density fixed and the total energy density of vacuum at a minimum. The mechanism is due to mode - reservoir interaction, whereupon virtual quantum processes give rise to an effective mode-mode attraction. A BCS condensate results. It has a massless and massy collective excitation, the latter identified with the inflaton. For an effective non dimensional mode-reservoir coupling constant, g approx 0.3, the order of magnitude of its mass is what is required to account for cosmological fluctuations i.e. O(10^-6 -> 10^-5)m_Planck.
A Primer for Black Hole Quantum Physics
Robert Brout,Serge Massar,Renaud Parentani,Philippe Spindel
Physics , 2007, DOI: 10.1016/0370-1573(95)00008-5
Abstract: The mechanisms which give rise to Hawking radiation are revealed by analyzing in detail pair production in the presence of horizons. In preparation for the black hole problem, three preparatory problems are dwelt with at length: pair production in an external electric field, thermalization of a uniformly accelerated detector and accelerated mirrors. In the light of these examples, the black hole evaporation problem is then presented. The leitmotif is the singular behavior of modes on the horizon which gives rise to a steady rate of production. Special emphasis is put on how each produced particle contributes to the mean albeit arising from a particular vacuum fluctuation. It is the mean which drives the semiclassical back reaction. This aspect is analyzed in more detail than heretofore and in particular its drawbacks are emphasized. It is the semiclassical theory which gives rise to Hawking's famous equation for the loss of mass of the black hole due to evaporation $dM/dt \simeq -1/M^2$. Black hole thermodynamics is derived from the evaporation process whereupon the reservoir character of the black hole is manifest. The relation to the thermodynamics of the eternal black hole through the Hartle--Hawking vacuum and the Killing identity are displayed. It is through the analysis of the fluctuations of the field configurations which give rise to a particular Hawking photon that the dubious character of the semiclassical theory is manifest. The present frontier of research revolves around this problem and is principally concerned with the fact that one calls upon energy scales that are greater than Planckian and the possibility of a non unitary evolution as well. These last subjects are presented in qualitative fashion only, so that this review stops at the threshold of quantum gravity.
La modernisation de l’enseignement-apprentissage des compétences de production orale en FLE ne peut plus attendre
Alain Brouté
Synergies Espagne , 2009,
Abstract: Pourquoi est-il si difficile de moderniser et d’innover méthodologiquement sur le terrain de l’enseignement-apprentissage des langues et, plus particulièrement, celui des langues étrangères ? La peur du changement ne justifie pas de telles difficultés d’autant plus que l’innovation n’est pas contradictoire avec le respect de l’expérience et des acquis. Or, aujourd’hui plus que jamais, nous avons besoin de cette modernisation pour faire face aux énormes mutations socioculturelles et socio-économiques que conna t notre monde et, ainsi, nous adapter et nous préparer au mieux à la diversité des changements de comportements, aux évolutions technologiques et des connaissances et, surtout, à celles des besoins de nos publics d’apprenants. Une telle modernisation requiert une attitude pour le moins bienveillante de ceux qui ont le pouvoir d’encourager ou de freiner l’innovation et, en premier lieu, tous les enseignants et les chercheurs travaillant sur ce terrain.
Entanglement and Thermodynamics of Black Hole Entropy
R. Brout
Physics , 2008, DOI: 10.1142/S0218271808014187
Abstract: Using simple conditions drawn from the stability of the cosmos in terms of vacuum energy density, the cut-off momentum of entanglement is related to the planckian mass. In so doing the black hole entropy is shown to be independent of the number of field species that contribute to vacuum fluctuations. And this is in spite of the fact that the number of field species is a linear multiplicand of the entanglement entropy when this latter is expressed in terms of the fundamental momentum cut-off of all fields.
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