28 research outputs found
Field theoretical approach to non-local interactions: 1d electrons and fermionic impurities
We apply a recently proposed path-integral approach to non-local bosonization
to a Thirring-like system modeling non-relativistic massless particles
interacting with localized fermionic impurities. We consider forward scattering
processes described by symmetric potentials including interactions between
charge, current, spin and spin-current densities. In the general
(spin-flipping) problem we obtain an effective action for the collective modes
of the model at T = 0, containing WZW-type terms. When spin-flipping processes
are disregarded the structure of the action is considerably simplified,
allowing us to derive exact expressions for the dispersion relations of
collective modes and two point fermionic correlation functions as functionals
of the potentials. Finally, as an example, we compute the momentum distribution
for the case in which electrons and impurities are coupled through spin and
spin-current densities only. The formulae we get suggest that our formalism
could be useful in order to seek for a mechanism able to restore Fermi liquid
behavior.Comment: 27 pages, Latex file, no figure
Interfaces with a single growth inhomogeneity and anchored boundaries
The dynamics of a one dimensional growth model involving attachment and
detachment of particles is studied in the presence of a localized growth
inhomogeneity along with anchored boundary conditions. At large times, the
latter enforce an equilibrium stationary regime which allows for an exact
calculation of roughening exponents. The stochastic evolution is related to a
spin Hamiltonian whose spectrum gap embodies the dynamic scaling exponent of
late stages. For vanishing gaps the interface can exhibit a slow morphological
transition followed by a change of scaling regimes which are studied
numerically. Instead, a faceting dynamics arises for gapful situations.Comment: REVTeX, 11 pages, 9 Postscript figure
Novel criticality in a model with absorbing states
We study a one-dimensional model which undergoes a transition between an
active and an absorbing phase. Monte Carlo simulations supported by some
additional arguments prompted as to predict the exact location of the critical
point and critical exponents in this model. The exponents and
follows from random-walk-type arguments. The exponents are found to be non-universal and encoded in the singular part of
reactivation probability, as recently discussed by H. Hinrichsen
(cond-mat/0008179). A related model with quenched randomness is also studied.Comment: 5 pages, 5 figures, generalized version with the continuously
changing exponent bet
Path-Integral bosonization of a non-local interaction and its application to the study of 1-d many-body systems
We extend the path-integral approach to bosonization to the case in which the
fermionic interaction is non-local. In particular we obtain a completely
bosonized version of a Thirring-like model with currents coupled by general
(symmetric) bilocal potentials. The model contains the Tomonaga-Luttinger model
as a special case; exploiting this fact we study the basic properties of the
1-d spinless fermionic gas: fermionic correlators, the spectrum of collective
modes, etc. Finally we discuss the generalization of our procedure to the
non-Abelian case, thus providing a new tool to be used in the study of 1-d
many-body systems with spin-flipping interactions.Comment: 26 pages LATEX, La Plata 94-0
One-dimensional spin-1/2 Heisenberg antiferromagnet in a weak external magnetic field
The one dimensional spin-1/2 Heisenberg antiferromagnet in a weak magnetic
field h is studied using the bosonization method. We derive a set of
renormalization group equations. The fixed point is reached when the field is
scaled to the value at which the system is quarter-filled. As the magnetic
field varies, a continuum line of fixed points is formed. We compute the
uniform longitudinal susceptibility . The singular behavior of
as is found to be contained in with a
non-universal constant. The spin-spin correlations in the magnetic field are
calculated.Comment: 5 pages, 1 figure, published on PR
SDM: Selective Dynamic Manipulation of Visualizations
In this paper we present a new set of interactive techniques for 2D and 3D visualizations. This set of techniques is called SDM (Selective Dynamic Manipulation). Selective, indicating our goal for providing a high degree of user control in selecting an object set, in selecting interactive techniques and the properties they affect, and in the degree to which a user action affects the visualization. Dynamic, indicating that the interactions all occur in real-time and that interactive animation is used to provide better contextual information to users in response to an action or operation. Manipulation, indicating the types of interactions we provide, where users can directly move objects and transform their appearance to perform different tasks. While many other approaches only provide interactive techniques in isolation, SDM supports a suite of techniques which users can combine to solve a wide variety of problems
SageBook: Searching data-graphics by content
Currently, there are many hypertext-like tools and database retrieval systems that use keyword search as a means of navigation. While useful for certain tasks, keyword search is insufficient for browsing databases of data-graphics. SageBook is a system that searches among existing data-graphics, so that they can be reused with new data. In order to fulfill the needs of retrieval and reuse, it provides: 1) a direct manipulation, graphical query interface, 2) a content description language that can express important relationships for retrieving data-graphics, 3) automatic description of stored data-graphics based on their content, 4) search techniques sensitive to the structure and similarity among data-graphics, 5) manual and automatic adaptation tools for altering data-graphics so that they can be reused with new data.