26 research outputs found
Reconstruction of Liouvillian Superoperators
We show how to determine (reconstruct) a master equation governing the time
evolution of an open quantum system.
We present a general algorithm for the reconstruction of the corresponding
Liouvillian superoperators. Dynamics of a two-level atom in various
environments is discussed in detail.Comment: 4 pages, revtex, 1 eps figure, accepted for publication in Phys. Rev.
Measurement models for time-resolved spectroscopy: a comment
We present an exactly solvable model for photon emission, which allows us to
examine the evolution of the photon wavefunction in space and time. We apply
this model to coherent phenomena in three-level systems with a special emphasis
on the photon detection process.Comment: 14 pages RevTex, 4 figure
Quantum Replicator Dynamics
We propose quantization relationships which would let us describe and
solution problems originated by conflicting or cooperative behaviors among the
members of a system from the point of view of quantum mechanical interactions.
The quantum analogue of the replicator dynamics is the equation of evolution of
mixed states from quantum statistical mechanics. A system and all its members
will cooperate and rearrange its states to improve their present condition.
They strive to reach the best possible state for each of them which is also the
best possible state for the whole system. This led us to propose a quantum
equilibrium in which a system is stable only if it maximizes the welfare of the
collective above the welfare of the individual. If it is maximized the welfare
of the individual above the welfare of the collective the system gets unstable
and eventually it collapses.Comment: 10 page
Performance of discrete heat engines and heat pumps in finite time
The performance in finite time of a discrete heat engine with internal
friction is analyzed. The working fluid of the engine is composed of an
ensemble of noninteracting two level systems. External work is applied by
changing the external field and thus the internal energy levels. The friction
induces a minimal cycle time. The power output of the engine is optimized with
respect to time allocation between the contact time with the hot and cold baths
as well as the adiabats. The engine's performance is also optimized with
respect to the external fields. By reversing the cycle of operation a heat pump
is constructed. The performance of the engine as a heat pump is also optimized.
By varying the time allocation between the adiabats and the contact time with
the reservoir a universal behavior can be identified. The optimal performance
of the engine when the cold bath is approaching absolute zero is studied. It is
found that the optimal cooling rate converges linearly to zero when the
temperature approaches absolute zero.Comment: 45 pages LaTeX, 25 eps figure
Singularities in the Fermi liquid description of a partially filled Landau level and the energy gaps of fractional quantum Hall states
We consider a two dimensional electron system in an external magnetic field
at and near an even denominator Landau level filling fraction. Using a
fermionic Chern--Simons approach we study the description of the system's low
energy excitations within an extension of Landau's Fermi liquid theory. We
calculate perturbatively the effective mass and the quasi--particle interaction
function characterizing this description. We find that at an even denominator
filling fraction the fermion's effective mass diverges logarithmically at the
Fermi level, and argue that this divergence allows for an {\it exact}
calculation of the energy gaps of the fractional quantized Hall states
asymptotically approaching these filling fractions. We find that the
quasi--particle interaction function approaches a delta function. This singular
behavior leads to a cancelation of the diverging effective mass from the long
wavelength low frequency linear response functions at even denominator filling
fractions.Comment: 46 pages, RevTeX, 5 figures included in a uuencoded postscript file.
Minor revisions relative to the original version. The paper will be published
in the Physical Review B, and can be retrieved from the World Wide Web, in
http://cmtw.harvard.edu/~ster
Dark matter as a QCD effect in an anti de Sitter geometry: Cosmogonic implications of de Sitter, anti de Sitter and Poincaré symmetries
34th International Colloquium on Group Theoretical Methods in PhysicsStrasbourg, 18-22 July 2022International audienceThe ΛCDM standard model of cosmology involves two dark components of the universe, dark energy and dark matter. Whereas dark energy is usually associated with the (positive) cosmological constant Λ associated with a de Sitter geometry, we propose to explain dark matter as a pure QCD effect, namely a gluonic Bose Einstein condensate with the status of a Cosmic Gluonic Background (CGB). This effect is due to the trace anomaly viewed as an effective negative cosmological constant determining an Anti de Sitter geometry and accompanying baryonic matter at the hadronization transition from the quark gluon plasma phase to the colorless hadronic phase. Our approach also allows to assume a ratio Dark/Visible equal to 11/2