11,787 research outputs found
Deformation Quantization of the Isotropic Rotator
We perform a deformation quantization of the classical isotropic rigid
rotator. The resulting quantum system is not invariant under the usual
chiral symmetry, but instead .Comment: 12pp, LATE
Two-parameter deformation of the Poincar\'e algebra
We examine a two-parameter ( ) deformation of the
Poincar\`e algebra which is covariant under the action of When
it yields the Poincar\`e algebra, while in the
limit we recover the classical quadratic algebra discussed
previously in \cite{ssy95}, \cite{sy95}. The analogues of the Pauli-Lubanski
vector and Casimirs and are found and a set of mutually
commuting operators is constructed.Comment: 10 pages, Latex2
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Selection-Based Learning: The Coevolution Of Internal And External Selection In High-Velocity Environments
To understand the effects of selection on firm-level learning, this study synthesizes two contrasting views of evolution. Internal selection theorists view managers in multiproduct firms as the primary agents of evolutionary change because they decide whether individual products and technologies are retained or eliminated. In contrast, external selection theorists contend that the environment drives evolution because it determines whether entire firms live or die. Though these theories differ, they describe tightly interwoven processes. In assessing the coevolution of internal and external selection among personal computer manufacturers across a 20-year period, we found that (1) firms learned cumulatively and adaptively from internal and partial external selection, the latter occurring when the environment killed part but not all of a firm; (2) internal and partial external selection coevolved, as each affected the other's future rate and the odds of firm failure; (3) partial external selection had a greater effect on future outcomes than internal selection; and (4) the lessons gleaned from prior selection were reflected in a firm's ability to develop new products, making that an important mediator between past and future selection events.Managemen
Proposed experiments to probe the non-abelian \nu=5/2 quantum Hall state
We propose several experiments to test the non-abelian nature of
quasi-particles in the fractional quantum Hall state of \nu=5/2. One set of
experiments studies interference contribution to back-scattering of current,
and is a simplified version of an experiment suggested recently. Another set
looks at thermodynamic properties of a closed system. Both experiments are only
weakly sensitive to disorder-induced distribution of localized quasi-particles.Comment: Additional references and an improved figure, 5 page
Properties of Quantum Hall Skyrmions from Anomalies
It is well known that the Fractional Quantum Hall Effect (FQHE) may be
effectively represented by a Chern-Simons theory. In order to incorporate QH
Skyrmions, we couple this theory to the topological spin current, and include
the Hopf term. The cancellation of anomalies for chiral edge states, and the
proviso that Skyrmions may be created and destroyed at the edge, fixes the
coefficients of these new terms. Consequently, the charge and the spin of the
Skyrmion are uniquely determined. For those two quantities we find the values
and , respectively, where is electron charge,
is the filling fraction and is the Skyrmion winding number. We
also add terms to the action so that the classical spin fluctuations in the
bulk satisfy the standard equations of a ferromagnet, with spin waves that
propagate with the classical drift velocity of the electron.Comment: 8 pages, LaTeX file; Some remarks are included to clarify the
physical results obtained, and the role of the Landau-Lifshitz equation is
emphasized. Some references adde
Lie-Poisson Deformation of the Poincar\'e Algebra
We find a one parameter family of quadratic Poisson structures on which satisfies the property {\it a)} that it is preserved
under the Lie-Poisson action of the Lorentz group, as well as {\it b)} that it
reduces to the standard Poincar\'e algebra for a particular limiting value of
the parameter. (The Lie-Poisson transformations reduce to canonical ones in
that limit, which we therefore refer to as the `canonical limit'.) Like with
the Poincar\'e algebra, our deformed Poincar\'e algebra has two Casimir
functions which we associate with `mass' and `spin'. We parametrize the
symplectic leaves of with space-time coordinates,
momenta and spin, thereby obtaining realizations of the deformed algebra for
the cases of a spinless and a spinning particle. The formalism can be applied
for finding a one parameter family of canonically inequivalent descriptions of
the photon.Comment: Latex file, 26 page
Lorentz Transformations as Lie-Poisson Symmetries
We write down the Poisson structure for a relativistic particle where the
Lorentz group does not act canonically, but instead as a Poisson-Lie group. In
so doing we obtain the classical limit of a particle moving on a noncommutative
space possessing invariance. We show that if the standard mass
shell constraint is chosen for the Hamiltonian function, then the particle
interacts with the space-time. We solve for the trajectory and find that it
originates and terminates at singularities.Comment: 18 page
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