177,715 research outputs found
Random Isotropic Structures and Possible Glass Transitions in Diblock Copolymer Melts
We study the microstructural glass transitions in diblock-copolymer melts
using a thermodynamic replica approach. Our approach performs an expansion in
terms of the natural smallness parameter -- the inverse of the scaled degree of
polymerization, which allows us to systematically study the approach to
mean-field behavior as the degree of polymerization increases. We find that in
the limit of infinite long polymer chains, both the onset of glassiness and the
vitrification transition (Kauzmann temperature) collapse to the mean-field
spinodal, suggesting that the spinodal can be regarded as the mean-field
signature for glass transitions in this class of systems. We also study the
order-disorder transitions (ODT) within the same theoretical framework; in
particular, we include the leading-order fluctuation corrections due to the
cubic interaction in the coarse-grained Hamiltonian, which has been ignored in
previous works on the ODT in block copolymers. We find that the cubic term
stabilizes both the ordered (body-centered-cubic) phase and the glassy state
relative to the disordered phase. While in melts of symmetric copolymers the
glass transition always occurs after the order-disorder transition (below the
ODT temperature), for asymmetric copolymers, it is possible that the glass
transition precedes the ordering transition.Comment: An error corrected in the referenc
Bayesian Species Delimitation Can Be Robust to Guide-Tree Inference Errors
distribution, and reproduction in any medium, provided the original work is properly cited
Effective hadronic Lagrangian for charm mesons
An effective hadronic Lagrangian including the charm mesons is introduced to
study their interactions in hadronic matter. Using coupling constants that are
determined either empirically or by the SU(4) symmetry, we have evaluated the
absorption cross sections of and the scattering cross sections of
and by and mesons.Comment: 5 pages, 4 eps figures, presented at Strangeness 2000, Berkeley. Uses
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Study of the ionic Peierls-Hubbard model using density matrix renormalization group methods
Density matrix renormalization group methods are used to investigate the
quantum phase diagram of a one-dimensional half-filled ionic Hubbard model with
bond-charge attraction, which can be mapped from the Su-Schrieffer-Heeger-type
electron-phonon coupling at the antiadiabatic limit. A bond order wave
(dimerized) phase which separates the band insulator from the Mott insulator
always exists as long as electron-phonon coupling is present. This is
qualitatively different from that at the adiabatic limit. Our results indicate
that electron-electron interaction, ionic potential and quantum phonon
fluctuations combine in the formation of the bond-order wave phase
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