10,457 research outputs found
Critical Exponents of the Chiral Potts Model from Conformal Field Theory
The -invariant chiral Potts model is considered as a perturbation of a
conformal field theory. In the self-dual case the renormalization group
equations become simple, and yield critical exponents and anisotropic scaling
which agree with exact results for the super-integrable lattice models.
Although the continuum theory is not Lorentz invariant, it respects a novel
type of space-time symmetry which allows for the observed spontaneous breaking
of translational symmetry in the ground state. The continuum theory is shown to
possess an infinite number of conserved charges on the self-dual line, which
remain conserved when the theory is perturbed by the energy operator.Comment: 15 page
Report drawn up on behalf of the Committee on Agriculture on the proposal from the Commission of the European Communities to the Council (Doc. 533/76) for a regulation laying down special measures in respect of the Beneventano variety of tobacco. EP Working Documents, document 549/76, 4 February 1977
Direction dependent free energy singularity of the asymmetric six-vertex model
The transition from the ordered commensurate phase to the incommensurate
gaussian phase of the antiferroelectric asymmetric six-vertex model is
investigated by keeping the temperature constant below the roughening point and
varying the external fields . In the plane, the phase boundary
is approached along straight lines , where measures the displacement from the phase boundary. It is found
that the free energy singularity displays the exponent 3/2 typical of the
Pokrovski-Talapov transition for any
direction other than the tangential one. In the latter case shows a
discontinuity in the third derivative.Comment: 18 pages, Latex, 1 figure, minor corrections and two references
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Notions of controllability for quantum mechanical systems
In this paper, we define four different notions of controllability of
physical interest for multilevel quantum mechanical systems. These notions
involve the possibility of driving the evolution operator as well as the state
of the system. We establish the connections among these different notions as
well as methods to verify controllability.
The paper also contains results on the relation between the controllability
in arbitrary small time of a system varying on a compact transformation Lie
group and the corresponding system on the associated homogeneous space. As an
application, we prove that, for the system of two interacting spin 1/2
particles, not every state transfer can be obtained in arbitrary small time.Comment: Replaced by a new version which contains the proof
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