18,712 research outputs found
Aging phenomena in polystyrene thin films
The aging behavior is investigated for thin films of atactic polystyrene
through measurements of complex electric capacitance. During isothermal aging
process the real part of the electric capacitance increases with aging time,
while the imaginary part decreases with aging time. This result suggests that
the aging time dependence of the real and imaginary parts are mainly associated
with change in thickness and dielectric permittivity, respectively. In thin
films, the thickness depends on thermal history of aging even above the glass
transition. Memory and `rejuvenation' effects are also observed in the thin
films.Comment: 4 pages, 2 figure
Exact spectrum of the XXZ open spin chain from the q-Onsager algebra representation theory
The transfer matrix of the XXZ open spin-1/2 chain with general integrable
boundary conditions and generic anisotropy parameter (q is not a root of unity
and |q|=1) is diagonalized using the representation theory of the q-Onsager
algebra. Similarly to the Ising and superintegrable chiral Potts models, the
complete spectrum is expressed in terms of the roots of a characteristic
polynomial of degree d=2^N. The complete family of eigenstates are derived in
terms of rational functions defined on a discrete support which satisfy a
system of coupled recurrence relations. In the special case of linear relations
between left and right boundary parameters for which Bethe-type solutions are
known to exist, our analysis provides an alternative derivation of the results
by Nepomechie et al. and Cao et al.. In the latter case the complete family of
eigenvalues and eigenstates splits in two sets, each associated with a
characteristic polynomial of degree . Numerical checks performed for
small values of support the analysis.Comment: 21 pages; LaTeX file with amssymb; v2: typos corrected, references
added, more details, to appear in JSTA
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