86 research outputs found
Finite temperature phase transition for disordered weakly interacting bosons in one dimension
It is commonly accepted that there are no phase transitions in
one-dimensional (1D) systems at a finite temperature, because long-range
correlations are destroyed by thermal fluctuations. Here we demonstrate that
the 1D gas of short-range interacting bosons in the presence of disorder can
undergo a finite temperature phase transition between two distinct states:
fluid and insulator. None of these states has long-range spatial correlations,
but this is a true albeit non-conventional phase transition because transport
properties are singular at the transition point. In the fluid phase the mass
transport is possible, whereas in the insulator phase it is completely blocked
even at finite temperatures. We thus reveal how the interaction between
disordered bosons influences their Anderson localization. This key question,
first raised for electrons in solids, is now crucial for the studies of atomic
bosons where recent experiments have demonstrated Anderson localization in
expanding very dilute quasi-1D clouds.Comment: 8 pages, 5 figure
Quantum biology on the edge of quantum chaos
We give a new explanation for why some biological systems can stay quantum
coherent for long times at room temperatures, one of the fundamental puzzles of
quantum biology. We show that systems with the right level of complexity
between chaos and regularity can increase their coherence time by orders of
magnitude. Systems near Critical Quantum Chaos or Metal-Insulator Transition
(MIT) can have long coherence times and coherent transport at the same time.
The new theory tested in a realistic light harvesting system model can
reproduce the scaling of critical fluctuations reported in recent experiments.
Scaling of return probability in the FMO light harvesting complex shows the
signs of universal return probability decay observed at critical MIT. The
results may open up new possibilities to design low loss energy and information
transport systems in this Poised Realm hovering reversibly between quantum
coherence and classicality
Unified Homogenization Theory for Magnetoinductive and Electromagnetic Waves in Split Ring Metamaterials
A unified homogenization procedure for split ring metamaterials taking into
account time and spatial dispersion is introduced. The procedure is based on
two coupled systems of equations. The first one comes from an approximation of
the metamaterial as a cubic arrangement of coupled LC circuits, giving the
relation between currents and local magnetic field. The second equation comes
from macroscopic Maxwell equations, and gives the relation between the
macroscopic magnetic field and the average magnetization of the metamaterial.
It is shown that electromagnetic and magnetoinductive waves propagating in the
metamaterial are obtained from this analysis. Therefore, the proposed time and
spatially dispersive permeability accounts for the characterization of the
complete spectrum of waves of the metamaterial. Finally, it is shown that the
proposed theory is in good quantitative and qualitative agreement with full
wave simulations.Comment: 4 pages, 3 figure
The Physics of the Intergalactic Medium
Intergalactic space is filled with a pervasive medium of ionized gas, the
Intergalactic Medium (IGM). A residual neutral fraction is detected in the
spectra of Quasi-Stellar Objects at both low and high redshifts, revealing a
highly fluctuating medium with temperatures characteristic of photoionized gas.
The statistics of the fluctuations are well-reproduced by numerical
gravity-hydrodynamics simulations within the context of standard cosmological
structure formation scenarios. As such, the study of the IGM offers an
opportunity to probe the nature of the primordial density fluctuations on
scales unavailable to other methods. The simulations also suggest the IGM is
the dominant reservoir of baryons produced by the Big Bang, and so the
principal source of the matter from which galaxies formed. The detection of
metal systems within the IGM shows that it was enriched by evolved stars early
in its history, demonstrating an intimate connection between galaxy formation
and the IGM. The author presents a comprehensive review of the current
understanding of the structure and physical properties of the IGM and its
relation to galaxies, concluding with comments on prospects for furthering the
study of the IGM using future ground-based facilities and space-based
experiments.Comment: 69 pages; accepted version to appear in Reviews of Modern Physics;
text and equation typos corrected; all figures include
Dependence of Hopping Conduction on the Impurity Concentration and Strain in the Crystal
Ultrasonic Velocity and Electrical Conductivity in p-InSb at Low Temperatures and High Magnetic Fields
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