Dr. Immanuel Gitamo - Academia.edu (original) (raw)

Papers by Dr. Immanuel Gitamo

Physical Review, 1966

The theory of the He II thermal counterflow process in wide (d&am... more The theory of the He II thermal counterflow process in wide (d>10-3 cm) channels is investigated on the assumption that both the normal and superfluid components make a transition from a laminar to a turbulent type of flow. A critical heat current W0 is identified with the superfluid transition. The superfluid turbulent state is taken to be essentially that described by Vinen in terms of quantized vortex line and has an associated mutual friction. A second critical heat current Wc is identified with the normal-fluid transition. It is argued that this transition is essentially of a classical turbulent type, with the added condition that the critical value of the Reynolds number must depend on the extent of mutual-friction coupling. This interpretation is shown to be consistent with experimentally observed critical heat currents, as well as with critical-velocity effects found in other types of flow. The assumption of two critical heat currents defines three distinct flow regions. It is shown that these three regions are essentially the same as those found experimentally by Allen, Griffiths, and Osborne. On the basis of some simplifying assumptions regarding the normal-fluid turbulent state, the temperature and pressure gradients accompanying thermal counterflow are calculated. Comparison with experiment shows good qualitative and often quantitative agreement. It is also shown that the model developed can be successfully used to interpret experiments involving flows of a nonthermal counterflow type.

The classical limit of the quantum mechanical Vlasov equation is a canonical Vlasov equation whic... more The classical limit of the quantum mechanical Vlasov equation is a canonical Vlasov equation which is generally different from the usual one. Therefore, one has to discriminate between the velocity operator v0= (p−esA0/c)/ms appearing in the vertex for transverse interactions and the true velocity operator v= (p−esA/c)/ms. It is shown that erroneous results for the dielectric tensor as obtained by Harris are explained by this fact.

Physics of Fluids, 1978

Attention is given to a distinction drawn between the velocity operator appearing in the vertex f... more Attention is given to a distinction drawn between the velocity operator appearing in the vertex for transverse interactions, and the true velocity operator in a canonical Vlasov equation. A magnetized plasma, or transversal waves in an unmagnetized plasma, are considered in terms of the classical limit of Harris' equation to point out previously obtained erroneous results for the dielectric tensor. It is noted that quantum mechanical conductivity is better illustrated by the inclusion of the Wigner function.

Physical Review, 1966

The theory of the He II thermal counterflow process in wide (d>10-3 cm) channels is investigated ... more The theory of the He II thermal counterflow process in wide (d>10-3 cm) channels is investigated on the assumption that both the normal and superfluid components make a transition from a laminar to a turbulent type of flow. A critical heat current W0 is identified with the superfluid transition. The superfluid turbulent state is taken to be essentially that described by Vinen in terms of quantized vortex line and has an associated mutual friction. A second critical heat current Wc is identified with the normal-fluid transition. It is argued that this transition is essentially of a classical turbulent type, with the added condition that the critical value of the Reynolds number must depend on the extent of mutual-friction coupling. This interpretation is shown to be consistent with experimentally observed critical heat currents, as well as with critical-velocity effects found in other types of flow. The assumption of two critical heat currents defines three distinct flow regions. It is shown that these three regions are essentially the same as those found experimentally by Allen, Griffiths, and Osborne. On the basis of some simplifying assumptions regarding the normal-fluid turbulent state, the temperature and pressure gradients accompanying thermal counterflow are calculated. Comparison with experiment shows good qualitative and often quantitative agreement. It is also shown that the model developed can be successfully used to interpret experiments involving flows of a nonthermal counterflow type.

Chaos Solitons & Fractals, 1998

Quantum Mechanics (Non-relativistic Theory) Course of Theoretical Physics Volume 3 Third Edition ... more Quantum Mechanics (Non-relativistic Theory) Course of Theoretical Physics Volume 3 Third Edition LD Landau and EM Lifshitz Institute of Physical Problems, USSR ...

Physical Review, 1966

The theory of the He II thermal counterflow process in wide (d&am... more The theory of the He II thermal counterflow process in wide (d>10-3 cm) channels is investigated on the assumption that both the normal and superfluid components make a transition from a laminar to a turbulent type of flow. A critical heat current W0 is identified with the superfluid transition. The superfluid turbulent state is taken to be essentially that described by Vinen in terms of quantized vortex line and has an associated mutual friction. A second critical heat current Wc is identified with the normal-fluid transition. It is argued that this transition is essentially of a classical turbulent type, with the added condition that the critical value of the Reynolds number must depend on the extent of mutual-friction coupling. This interpretation is shown to be consistent with experimentally observed critical heat currents, as well as with critical-velocity effects found in other types of flow. The assumption of two critical heat currents defines three distinct flow regions. It is shown that these three regions are essentially the same as those found experimentally by Allen, Griffiths, and Osborne. On the basis of some simplifying assumptions regarding the normal-fluid turbulent state, the temperature and pressure gradients accompanying thermal counterflow are calculated. Comparison with experiment shows good qualitative and often quantitative agreement. It is also shown that the model developed can be successfully used to interpret experiments involving flows of a nonthermal counterflow type.

The classical limit of the quantum mechanical Vlasov equation is a canonical Vlasov equation whic... more The classical limit of the quantum mechanical Vlasov equation is a canonical Vlasov equation which is generally different from the usual one. Therefore, one has to discriminate between the velocity operator v0= (p−esA0/c)/ms appearing in the vertex for transverse interactions and the true velocity operator v= (p−esA/c)/ms. It is shown that erroneous results for the dielectric tensor as obtained by Harris are explained by this fact.

Physics of Fluids, 1978

Attention is given to a distinction drawn between the velocity operator appearing in the vertex f... more Attention is given to a distinction drawn between the velocity operator appearing in the vertex for transverse interactions, and the true velocity operator in a canonical Vlasov equation. A magnetized plasma, or transversal waves in an unmagnetized plasma, are considered in terms of the classical limit of Harris' equation to point out previously obtained erroneous results for the dielectric tensor. It is noted that quantum mechanical conductivity is better illustrated by the inclusion of the Wigner function.

Physical Review, 1966

The theory of the He II thermal counterflow process in wide (d>10-3 cm) channels is investigated ... more The theory of the He II thermal counterflow process in wide (d>10-3 cm) channels is investigated on the assumption that both the normal and superfluid components make a transition from a laminar to a turbulent type of flow. A critical heat current W0 is identified with the superfluid transition. The superfluid turbulent state is taken to be essentially that described by Vinen in terms of quantized vortex line and has an associated mutual friction. A second critical heat current Wc is identified with the normal-fluid transition. It is argued that this transition is essentially of a classical turbulent type, with the added condition that the critical value of the Reynolds number must depend on the extent of mutual-friction coupling. This interpretation is shown to be consistent with experimentally observed critical heat currents, as well as with critical-velocity effects found in other types of flow. The assumption of two critical heat currents defines three distinct flow regions. It is shown that these three regions are essentially the same as those found experimentally by Allen, Griffiths, and Osborne. On the basis of some simplifying assumptions regarding the normal-fluid turbulent state, the temperature and pressure gradients accompanying thermal counterflow are calculated. Comparison with experiment shows good qualitative and often quantitative agreement. It is also shown that the model developed can be successfully used to interpret experiments involving flows of a nonthermal counterflow type.

Chaos Solitons & Fractals, 1998

Quantum Mechanics (Non-relativistic Theory) Course of Theoretical Physics Volume 3 Third Edition ... more Quantum Mechanics (Non-relativistic Theory) Course of Theoretical Physics Volume 3 Third Edition LD Landau and EM Lifshitz Institute of Physical Problems, USSR ...