731 research outputs found
Can the frequency-dependent specific heat be measured by thermal effusion methods?
It has recently been shown that plane-plate heat effusion methods devised for
wide-frequency specific-heat spectroscopy do not give the isobaric specific
heat, but rather the so-called longitudinal specific heat. Here it is shown
that heat effusion in a spherical symmetric geometry also involves the
longitudinal specific heat.Comment: Paper presented at the Fifth International Workshop on Complex
Systems (Sendai, September, 2007), to appear in AIP Conference Proceeding
Fluctuation effects in the theory of microphase separation of diblock copolymers in the presence of an electric field
We generalize the Fredrickson-Helfand theory of the microphase separation in
symmetric diblock copolymer melts by taking into account the influence of a
time-independent homogeneous electric field on the composition fluctuations
within the self-consistent Hartree approximation. We predict that electric
fields suppress composition fluctuations, and consequently weaken the
first-order transition. In the presence of an electric field the critical
temperature of the order-disorder transition is shifted towards its mean-field
value. The collective structure factor in the disordered phase becomes
anisotropic in the presence of the electric field. Fluctuational modulations of
the order parameter along the field direction are strongest suppressed. The
latter is in accordance with the parallel orientation of the lamellae in the
ordered state.Comment: 16 page
Novel Extrapolation Method in the Monte Carlo Shell Model
We propose an extrapolation method utilizing energy variance in the Monte
Carlo shell model in order to estimate the energy eigenvalue and observables
accurately. We derive a formula for the energy variance with deformed Slater
determinants, which enables us to calculate the energy variance efficiently.
The feasibility of the method is demonstrated for the full -shell
calculation of Ni, and the applicability of the method to a system
beyond current limit of exact diagonalization is shown for the
+-shell calculation of Ge.Comment: 4 pages, 4figure
Ultra-violet Behavior of Bosonic Quantum Membranes
We treat the action for a bosonic membrane as a sigma model, and then compute
quantum corrections by integrating out higher membrane modes. As in string
theory, where the equations of motion of Einstein's theory emerges by setting
, we find that, with certain assumptions, we can recover the
equations of motion for the background fields. Although the membrane theory is
non-renormalizable on the world volume by power counting, the investigation of
the ultra-violet behavior of membranes may give us insight into the
supersymmetric case, where we hope to obtain higher order M-theory corrections
to 11 dimensional supergravity.Comment: 25 pages, Latex, no figure
Magic numbers in exotic nuclei and spin-isospin properties of {\it NN} interaction
The magic numbers in exotic nuclei are discussed, and their novel origin is
shown to be the spin-isospin dependent part of the nucleon-nucleon interaction
in nuclei. The importance and robustness of this mechanism is shown in terms of
meson exchange, G-matrix and QCD theories. In neutron-rich exotic nuclei, magic
numbers such as N = 8, 20, etc. can disappear, while N = 6, 16, etc. arise,
affecting the structure of lightest exotic nuclei to nucleosynthesis of heavy
elements.Comment: 4 pages, 3 figures, revte
Nuclear Shell Model by the Quantum Monte Carlo Diagonalization Method
The feasibility of shell-model calculations is radically extended by the
Quantum Monte Carlo Diagonalization method with various essential improvements.
The major improvements are made in the sampling for the generation of
shell-model basis vectors, and in the restoration of symmetries such as angular
momentum and isospin. Consequently the level structure of low-lying states can
be studied with realistic interactions. After testing this method on Mg,
we present first results for energy levels and properties of Ge,
indicating its large and -soft deformation.Comment: 12 pages, RevTex, 2 figures, to be published in Physical Review
Letter
QKZ equation with |q|=1 and correlation functions of the XXZ model in the gapless regime
An integral solution to the quantum Knizhnik-Zamolodchikov (KZ) equation
with is presented. Upon specialization, it leads to a conjectural
formula for correlation functions of the XXZ model in the gapless regime. The
validity of this conjecture is verified in special cases, including the nearest
neighbor correlator with an arbitrary coupling constant, and general
correlators in the XXX and XY limits
Coulomb Blockade and Coherent Single-Cooper-Pair Tunneling in Single Josephson Junctions
We have measured the current-voltage characteristics of small-capacitance
single Josephson junctions at low temperatures (T < 0.04 K), where the strength
of the coupling between the single junction and the electromagnetic environment
was controlled with one-dimensional arrays of dc SQUIDs. We have clearly
observed Coulomb blockade of Cooper-pair tunneling and even a region of
negative differential resistance, when the zero-bias resistance of the SQUID
arrays is much higher than the quantum resistance h/e^2 = 26 kohm. The negative
differential resistance is evidence of coherent single-Cooper-pair tunneling in
the single Josephson junction.Comment: RevTeX, 4 pages with 6 embedded figure
A quantum homogeneous space of nilpotent matrices
A quantum deformation of the adjoint action of the special linear group on
the variety of nilpotent matrices is introduced. New non-embedded quantum
homogeneous spaces are obtained related to certain maximal coadjoint orbits,
and known quantum homogeneous spaces are revisited.Comment: 12 page
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