Macroscopical matter derived from quantum field theory

Domenech, Graciela; Levinas, Marcelo Leonardo

doi:10.1016/s0378-4371(99)00549-x

Cited by 2 publications

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References 4 publications

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“…Refs. [14], and recently deduced classical fluid behavior of quantum fields in WKB approximation [6], we study the full quantum effects here.…”

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Fluid dynamics of relativistic quantum dust

Elze¹

2002

J. Phys. G: Nucl. Part. Phys.

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The microscopic transport equations for free fields are solved using the Schwinger function. Thus, for general initial conditions, the evolution of the energy-momentum tensor is obtained, incorporating the quantum effects exactly. The result for relativistic fermions differs from classical hydrodynamics, which is illustrated for Landau and Bjorken type initial conditions in this model of exploding primordial matter. Free fermions behave like classical dust concerning hydrodynamic observables. However, quantum effects which are present in the initial state are preserved. PACS numbers:Often the complicated time dependent dynamics of quantum many-body systems or fields is approximated by a perfect fluid model. Since the seminal work by Fermi and Landau this approach has been applied successfully, in order to study global features, such as multiplicity distributions and apparently thermal transverse momentum spectra of produced particles, in high-energy collisions of strongly interacting matter [1,2,3,4]. Similarly, the hydrodynamic approximation is often invoked in astrophysical applications and cosmological studies of the early universe [5] Recently it has been shown that a free scalar field indeed behaves like a perfect fluid in the semiclassical (WKB) regime [6]. More generally, the mechanisms of quantum decoherence and thermalization in such systems which can be described hydrodynamically, i.e. the emergence of classical deterministic evolution from an underlying quantum field theory, are of fundamental interest [7,8,9,10].The limitations of the fluid picture, however, have rarely been explored in the microscopic or high energy density domain. Difficulties reside in the derivation of consistent transport equations and in the amount of computation required to find realistic solutions; see Refs. [11], for example, for a review and recent progress concerning selfinteracting scalar particles and the quark-gluon plasma, respectively. More understanding of related hydrodynamic behavior, if any, seems highly desirable.Presently, we study the relation between relativistic hydrodynamics and the full quantum evolution of a free matter field. In the absence of interactions, decoherence or thermalization may be present in the initial state, corresponding to an impure density matrix, but is followed by unitary evolution. We consider this as a "quantum dust" model of the expansion of matter originating from a high energy density preparation phase, which the Landau and Bjorken models describe classically [2,3].Our approach is independent of the nature of the field, as long as it obeys a standard wave equation. To be definite, we choose to work with Dirac fermions and comment about neutrinos later. We introduce the spinor Wigner function, i.e., a (4x4)-matrix depending on space-time and four-momentum coordinates:

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“…Refs. [14], and recently deduced classical fluid behavior of quantum fields in WKB approximation [6], we study the full quantum effects here.…”

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confidence: 99%

“…which is symmetric and conserved, ∂ µ T µν (x) = 0, on account of Eq. (6). Furthermore, this implies the 'equation of state':…”

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confidence: 99%

Fluid dynamics of relativistic quantum dust

Elze¹

2002

J. Phys. G: Nucl. Part. Phys.

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“…Refs. [31], and recently deduced classical fluid behavior of quantum fields in WKB approximation [9], however, we study the full quantum evolution here.…”

Section: Fluid Dynamics Of Relativistic Quantum Dustmentioning

confidence: 99%

“…This does not depend on whether the initial state is on-or off-shell, see Eq.(80). Therefore, any hydrodynamic behavior must be the effect of a pecularity of the semiclassical limit [9], of coarse graining [11,12,13], or of interactions [32], or a combination of these.…”

Section: Fluid Dynamics Of Relativistic Quantum Dustmentioning

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Relativistic Quantum Transport Theory

Elze¹

2002

AIP Conference Proceedings

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Relativistic quantum transport theory has begun to play an important role in the space-time description of matter under extreme conditions of high energy density in out-of-equilibrium situations. The following introductory lectures on some of its basic concepts and methods comprise the sections: 1. Introduction; 2. Aims of transport theory (classical); 3. Quantum mechanical distribution functions - the density matrix and the Wigner function; 4. Transport theory for quantum fields; 5. Particle production by classical fields; 6. Fluid dynamics of relativistic quantum dust.Comment: Lectures presented at PASI "New States of Matter in Hadronic Interactions", Campos do Jordao, Brazil, Jan.7-18, 2002. - 19 pages; LaTe

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Macroscopical matter derived from quantum field theory

Cited by 2 publications

References 4 publications

Fluid dynamics of relativistic quantum dust

Fluid dynamics of relativistic quantum dust

Relativistic Quantum Transport Theory

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