1,588 research outputs found
Quantum Hall Effect on the Flag Manifold F_2
The Landau problem on the flag manifold
is analyzed from an algebraic point of view. The involved magnetic background
is induced by two U(1) abelian connections. In quantizing the theory, we show
that the wavefunctions, of a non-relativistic particle living on ,
are the SU(3) Wigner -functions satisfying two constraints. Using the
algebraic and geometrical structures, we derive the Landau
Hamiltonian as well as its energy levels. The Lowest Landau level (LLL)
wavefunctions coincide with the coherent states for the mixed SU(3)
representations. We discuss the quantum Hall effect for a filling factor . where the obtained particle density is constant and finite for a strong
magnetic field. In this limit, we also show that the system behaves like an
incompressible fluid. We study the semi-classical properties of the system
confined in LLL. These will be used to discuss the edge excitations and
construct the corresponding Wess-Zumino-Witten action.Comment: 23 pages, two sections and references added, misprints corrected,
version to appear in IJMP
Coherent and generalized intelligent states for infinite square well potential and nonlinear oscillators
This article is an illustration of the construction of coherent and
generalized intelligent states which has been recently proposed by us for an
arbitrary quantum system . We treat the quantum system submitted to the
infinite square well potential and the nonlinear oscillators. By means of the
analytical representation of the coherent states \`{a} la Gazeau-Klauder and
those \`{a} la Klauder-Perelomov, we derive the generalized intelligent states
in analytical ways
Effective interactions between star polymers
We study numerically the effective pair potential between star polymers with
equal arm lengths and equal number of arms. The simulations were done for
the soft core Domb-Joyce model on the simple cubic lattice, to minimize
corrections to scaling and to allow for an unlimited number of arms. For the
sampling, we used the pruned-enriched Rosenbluth method (PERM). We find that
the potential is much less soft than claimed in previous papers, in particular
for . While we verify the logarithmic divergence of , with
being the distance between the two cores, predicted by Witten and Pincus, we
find for that the Mayer function is hardly distinguishable from that for
a Gaussian potential.Comment: 5 pages, 5 figure
Scaling theory of DNA confined in nanochannels and nanoslits
A scaling analysis is presented of the statistics of long DNA confined in
nanochannels and nanoslits. It is argued that there are several regimes in
between the de Gennes and Odijk limits introduced long ago. The DNA chain folds
back on itself giving rise to a global persistence length which may be very
large owing to entropic deflection. Moreover, there is an orientational
excluded-volume effect between the DNA segments imposed solely by the
nanoconfinement. These two effects cause the chain statistics to be intricate
leading to nontrivial power laws for the chain extension in the intermediate
regimes. It is stressed that DNA confinement within nanochannels differs from
that in nanoslits because the respective orientational excluded-volume effects
are not the same.Comment: 5 pages, 1 figure Several corrections, some minor changes in the text
and replacement of one referenc
Structure of bottle-brush brushes under good solvent conditions. A molecular dynamics study
We report a simulation study for bottle-brush polymers grafted on a rigid
backbone. Using a standard coarse-grained bead-spring model extensive molecular
dynamics simulations for such macromolecules under good solvent conditions are
performed. We consider a broad range of parameters and present numerical
results for the monomer density profile, density of the untethered ends of the
grafted flexible backbones and the correlation function describing the range
that neighboring grafted bottle-brushes are affected by the presence of the
others due to the excluded volume interactions. The end beads of the flexible
backbones of the grafted bottle-brushes do not access the region close to the
rigid backbone due to the presence of the side chains of the grafted
bottle-brush polymers, which stretch further the chains in the radial
directions. Although a number of different correlation lengths exist as a
result of the complex structure of these macromolecules, their properties can
be tuned with high accuracy in good solvents. Moreover, qualitative differences
with "typical" bottle-brushes are discussed. Our results provide a first
approach to characterizing such complex macromolecules with a standard bead
spring model.Comment: To appear in Journal of Physics Condensed Matter (2011
Phase operators, temporally stable phase states, mutually unbiased bases and exactly solvable quantum systems
We introduce a one-parameter generalized oscillator algebra A(k) (that covers
the case of the harmonic oscillator algebra) and discuss its finite- and
infinite-dimensional representations according to the sign of the parameter k.
We define an (Hamiltonian) operator associated with A(k) and examine the
degeneracies of its spectrum. For the finite (when k < 0) and the infinite
(when k > 0 or = 0) representations of A(k), we construct the associated phase
operators and build temporally stable phase states as eigenstates of the phase
operators. To overcome the difficulties related to the phase operator in the
infinite-dimensional case and to avoid the degeneracy problem for the
finite-dimensional case, we introduce a truncation procedure which generalizes
the one used by Pegg and Barnett for the harmonic oscillator. This yields a
truncated generalized oscillator algebra A(k,s), where s denotes the truncation
order. We construct two types of temporally stable states for A(k,s) (as
eigenstates of a phase operator and as eigenstates of a polynomial in the
generators of A(k,s)). Two applications are considered in this article. The
first concerns physical realizations of A(k) and A(k,s) in the context of
one-dimensional quantum systems with finite (Morse system) or infinite
(Poeschl-Teller system) discrete spectra. The second deals with mutually
unbiased bases used in quantum information.Comment: Accepted for publication in Journal of Physics A: Mathematical and
Theoretical as a pape
Incommensurate magnetic ordering in (X=Cl,Br) studied by neutron diffraction
We present the results of the first neutron powder and single crystal
diffraction studies of the coupled spin tetrahedra systems {\CuTeX} (X=Cl,
Br). Incommensurate antiferromagnetic order with the propagation vectors
{\bf{k}_{Cl}}\approx[0.150,0.422,\half],
{\bf{k}_{Br}}\approx[0.158,0.354,\half] sets in below =18 K for X=Cl
and 11 K for X=Br. No simple collinear antiferromagnetic or ferromagnetic
arrangements of moments within Cu tetrahedra fit these observations.
Fitting the diffraction data to more complex but physically reasonable models
with multiple helices leads to a moment of 0.67(1)/Cu at 1.5 K
for the Cl-compound. The reason for such a complex ground state may be
geometrical frustration of the spins due to the intra- and inter-tetrahedral
couplings having similar strengths. The magnetic moment in the Br- compound,
calculated assuming it has the same magnetic structure as the Cl compound, is
only 0.51(5)/Cu at 1.5 K. In neither compound has any evidence
for a structural transition accompanying the magnetic ordering been found
Aggregation number distributions and mesoglobules in dilute solutions of diblock and triblock copolymers
We investigate the aggregation number and size distributions for
inter-molecular clusters of amphiphilic diblock and triblock copolymers in poor
solvent at very low concentrations. Diblocks and triblocks with hydrophilic
ends are shown to possess narrow distributions corresponding to formation of
monodispersed mesoglobules. Diblocks with hydrophobic ends are found to produce
inter-cluster multimers due to bridging by the hydrophilic middle blocks,
resulting in polydisperse distributions. Implications of these observations for
preparation of monodispersed nanoparticles and, potentially, understanding of
the quaternary structure of proteins are discussed.Comment: 4 pages, 4 PS figures. Accepted for publication in EP
Symplectic Fluctuations for Electromagnetic Excitations of Hall Droplets
We show that the integer quantum Hall effect systems in plane, sphere or
disc, can be formulated in terms of an algebraic unified scheme. This can be
achieved by making use of a generalized Weyl--Heisenberg algebra and
investigating its basic features. We study the electromagnetic excitation and
derive the Hamiltonian for droplets of fermions on a two-dimensional Bargmann
space (phase space). This excitation is introduced through a deformation
(perturbation) of the symplectic structure of the phase space. We show the
major role of Moser's lemma in dressing procedure, which allows us to eliminate
the fluctuations of the symplectic structure. We discuss the emergence of the
Seiberg--Witten map and generation of an abelian noncommutative gauge field in
the theory. As illustration of our model, we give the action describing the
electromagnetic excitation of a quantum Hall droplet in two-dimensional
manifold.Comment: 23 page
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