1,763 research outputs found
CP_N Solitons in Quantum Hall Systems
We will present here an elementary pedagogical introduction to
solitons in quantum Hall systems. We begin with a brief introduction to both
models and to quantum Hall (QH) physics. Then we focus on spin and
layer-spin degrees of freedom in QH systems and point out that these are in
fact fields for N=1 and N=3. Excitations in these degrees of freedom
will be shown to be topologically non-trivial soliton solutions of the
corresponding field equations. This is followed by a brief summary of
our own recent work in this area, done with Sankalpa Ghosh. [ Invited Plenary
Lecture at the International Conference on Geometry, Integrability and
Nonlinearity in Condensed Matter & Soft Condensed Matter Physics held at
Bansko, Bulgaria, July 15-20, 2001. ]Comment: Standard revtex format, 18 pages, no figure
Bimerons in Double Layer Quantum Hall Systems
In this paper we discuss bimeron pseudo spin textures for double layer
quantum hall systems with filling factor . Bimerons are excitations
corresponding to bound pairs of merons and anti-merons.
Bimeron solutions have already been studied at great length by other groups
by minimising the microsopic Hamiltonian between microscopic trial
wavefunctions. Here we calculate them by numerically solving coupled nonlinear
partial differential equations arising from extremisation of the effective
action for pseudospin textures. We also calculate the different contributions
to the energy of our bimerons, coming from pseudospin stiffness, capacitance
and coulomb interactions between the merons. Apart from augmenting earlier
results, this allows us to check how good an approximation it is to think of
the bimeron as a pair of rigid objects (merons) with logarithmically growing
energy, and with electric charge . Our differential equation
approach also allows us to study the dependence of the spin texture as a
function of the distance between merons, and the inter layer distance. Lastly,
the technical problem of solving coupled nonlinear partial differential
equations, subject to the special boundary conditions of bimerons is
interesting in its own right.Comment: 8 ps figures included; to be published in IJMP
Quantum Hall Solitons with Intertwined Spin and Pseudospin at $\nu = \ 1$
In this paper we study in detail different types of topological solitons
which are possible in bilayer quantum Hall systems at filling fraction
when spin degrees of freedom are included. Starting from a microscopic
Hamiltonian we derive an effective energy functional for studying such
excitations. The gauge invariance and character of this energy
fuctional and their consequences are examined. Then we identify permissible
classes of finite energy solutions which are topologically non-trivial. We also
numerically evaulate a representative solution in which a pseudospin (layer
degrees of freedom) bimeron in a given spin component is intertwined with
spin-skyrmions in each layer, and and discuss whether it is energetically
favoured as the lowest lying excitation in such system with some numerical
results.Comment: Revised version with more numerical results one more figure and table
added. Total 32 pages,6 Postscript figures. Correspondence to
[email protected]
Meron Pseudospin Solutions in Quantum Hall Systems
In this paper we report calculations of some pseudospin textures for bilayer
quantum hall systems with filling factor . The textures we study are
isolated single meron solutions. Meron solutions have already been studied at
great length by others by minimising the microscopic Hamiltonian between
microscopic trial wavefunctions. Our approach is somewhat different. We
calculate them by numerically solving the nonlinear integro -differential
equations arising from extremisation of the effective action for pseudospin
textures. Our results can be viewed as augmenting earlier results and providing
a basis for comparison.Our differential equation approach also allows us to
dilineate the impact of different physical effects like the pseudospin
stiffness and the capacitance energy on the meron solution.Comment: 17 pages Revtex+ 4 Postscript figures; To appear in Int. J. Mod.
Phys.
A Field Theory for the Read Operator
We introduce a new field theory for studying quantum Hall systems. The
quantum field is a modified version of the bosonic operator introduced by Read.
In contrast to Read's original work we do {\em not} work in the lowest Landau
level alone, and this leads to a much simpler formalism. We identify an
appropriate canonical conjugate field, and write a Hamiltonian that governs the
exact dynamics of our bosonic field operators. We describe a Lagrangian
formalism, derive the equations of motion for the fields and present a family
of mean-field solutions. Finally, we show that these mean field solutions are
precisely the Laughlin states. We do not, in this work, address the treatment
of fluctuations.Comment: 15 pages, Revtex 3.
Landau Level Mixing and Solenoidal Terms in Lowest Landau Level Currents
We calculate the lowest Landau level (LLL) current by working in the full
Hilbert space of a two dimensional electron system in a magnetic field and
keeping all the non-vanishing terms in the high field limit. The answer a) is
not represented by a simple LLL operator and b) differs from the current
operator, recently derived by Martinez and Stone in a field theoretic LLL
formalism, by solenoidal terms. Though that is consistent with the inevitable
ambiguities of their Noether construction, we argue that the correct answer
cannot arise naturally in the LLL formalism.Comment: 12 pages + 2 figures, Revtex 3.0, UIUC preprint P-94-04-029, (to
appear in Mod. Phys. Lett. B
Near Horizon Superspace
The adS_{p+2} x S^{d-p-2} geometry of the near horizon branes is promoted to
a supergeometry: the solution of the supergravity constraints for the vielbein,
connection and form superfields are found. This supergeometry can be used for
the construction of new superconformal theories. We also discuss the
Green-Schwarz action for a type IIB string on adS_5 x S_5.Comment: 11 pages, LaTe
Higgs Localization in Split Fermion Models
The flavor puzzle of the Standard Model is explained in split fermion models
by having the fermions localized and separated in an extra dimension. Many of
these models assume a certain profile for the Higgs VEV, usually uniform, or
confined to a brane, without providing a dynamical realization for it. By
studying the effect of the coupling between the Higgs and the localizer fields,
we obtain these scenarios as results, rather than ansaetze. Moreover, we
discuss other profiles and show that they are phenomenologically viable.Comment: 23 pages, 16 figures, based on an MSc thesi
- …