4,785 research outputs found
Non-Newtonian Gravity, Fluctuative Hypothesis and the Sizes of Astrophysical Structures
We show that the characteristic sizes of astrophysical and cosmological
structures, where gravity is the only overall relevant interaction assembling
the system, have a phenomenological relation to the microscopic scales whose
order of magnitude is essentially ruled by the Compton wavelength of the
proton. This result agrees with the absence of screening mechanisms for the
gravitational interaction and could be connected to the presence of Yukawa
correcting terms in the Newtonian potential which introduce typical interaction
lengths. Furthermore, we are able to justify, in a straightforward way, the
Sanders--postulated mass of a vector boson considered in order to obtain the
characteristic sizes of galaxies.Comment: 11 pages. to appear in Mod. Phys. Lett.
Theory of warm ionized gases: equation of state and kinetic Schottky anomaly
Based on accurate Lennard-Jones type interaction potentials, we derive a
closed set of state equations for the description of warm atomic gases in the
presence of ionization processes. The specific heat is predicted to exhibit
peaks in correspondence to single and multiple ionizations. Such kinetic
analogue in atomic gases of the Schottky anomaly in solids is enhanced at
intermediate and low atomic densities. The case of adiabatic compression of
noble gases is analyzed in detail and the implications on sonoluminescence are
discussed. In particular, the predicted plasma electron density in a
sonoluminescent bubble turns out to be in good agreement with the value
measured in recent experiments.Comment: 7 pages, 4 figures, replaced with published versio
Modular Entanglement
We introduce and discuss the concept of modular entanglement. This is the
entanglement that is established between the end points of modular systems
composed by sets of interacting moduli of arbitrarily fixed size. We show that
end-to-end modular entanglement scales in the thermodynamic limit and rapidly
saturates with the number of constituent moduli. We clarify the mechanisms
underlying the onset of entanglement between distant and non-interacting
quantum systems and its optimization for applications to quantum repeaters and
entanglement distribution and sharing.Comment: 4 pages, 6 figure
Quantum localization and bound state formation in Bose-Einstein condensates
We discuss the possibility of exponential quantum localization in systems of
ultracold bosonic atoms with repulsive interactions in open optical lattices
without disorder. We show that exponential localization occurs in the maximally
excited state of the lowest energy band. We establish the conditions under
which the presence of the upper energy bands can be neglected, determine the
successive stages and the quantum phase boundaries at which localization
occurs, and discuss schemes to detect it experimentally by visibility
measurements. The discussed mechanism is a particular type of quantum
localization that is intuitively understood in terms of the interplay between
nonlinearity and a bounded energy spectrum.Comment: 6 pages, 5 figure
Probing Quantum Frustrated Systems via Factorization of the Ground State
The existence of definite orders in frustrated quantum systems is related
rigorously to the occurrence of fully factorized ground states below a
threshold value of the frustration. Ground-state separability thus provides a
natural measure of frustration: strongly frustrated systems are those that
cannot accommodate for classical-like solutions. The exact form of the
factorized ground states and the critical frustration are determined for
various classes of nonexactly solvable spin models with different spatial
ranges of the interactions. For weak frustration, the existence of
disentangling transitions determines the range of applicability of mean-field
descriptions in biological and physical problems such as stochastic gene
expression and the stability of long-period modulated structures.Comment: 4 pages, 2 figures. Replaced with published versio
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