131 research outputs found
Dilute Bose gas: short-range particle correlations and ultraviolet divergence
The modified Bogoliubov model where the primordial interaction is replaced by
the t matrix is reinvestigated. It is shown to provide a negative value of the
kinetic energy for a strongly interacting dilute Bose gas, contrary to the
original Bogoliubov model. To clear up the origin of this failure, the correct
values of the kinetic and interaction energies of a dilute Bose gas are
calculated. It is demonstrated that both the problem of the negative kinetic
energy and the ultraviolet divergence, dating back to the well-known paper of
Lee, Yang and Huang, is connected with an inadequate picture of the short-range
boson correlations. These correlations are reconsidered within the
thermodynamically consistent model proposed earlier by the present authors.
Found results are in absolute agreement with the data of the Monte-Carlo
calculations for the hard-sphere Bose gas.Comment: 11 pages, REVTeX, 2 figures inserte
Towards a New Strategy of Searching for QCD Phase Transition in Heavy Ion Collisions
We reconsider the Hung and Shuryak arguments in favour of searching for the
deconfinement phase transition in heavy ion collisions {\em downward} from the
nominal SPS energy, at where the fireball lifetime
is the longest one. Using the recent lattice QCD data and the mixed phase
model, we show that the deconfinement transition might occur at the bombarding
energies as low as . Attention is drawn to the study of
the mixed phase of nuclear matter in the collision energy range .Comment: 12 pages, latex file, figures available upon reques
Screening of pair fluctuations in superconductors with coupled shallow and deep bands: a route to higher temperature superconductivity
A combination of strong Cooper pairing and weak superconducting fluctuations
is crucial to achieve and stabilize high-Tc superconductivity. We demonstrate
that a coexistence of a shallow carrier band with strong pairing and a deep
band with weak pairing, together with the Josephson-like pair transfer between
the bands to couple the two condensates, realizes an optimal multicomponent
superconductivity regime: it preserves strong pairing to generate large gaps
and a very high critical temperature but screens the detrimental
superconducting fluctuations, thereby suppressing the pseudogap state.
Surprisingly, we find that the screening is very efficient even when the
inter-band coupling is very small. Thus, a multi-band superconductor with a
coherent mixture of condensates in the BCS regime (deep band) and in the
BCS-BEC crossover regime (shallow band) offers a promising route to higher
critical temperatures.Comment: 8 pages, 1 figure, including supplemental material
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