90,270 research outputs found
On Normal Forms for Levi-flat hypersurfaces with an Isolated Line Singularity
We prove the existence of normal forms for some local real-analytic Levi-flat
hypersurfaces with an isolated line singularity. We also give sufficient
conditions for that a Levi-flat hypersurface with a complex line as singularity
to be a pullback of a real-analytic curve in C via a holomorphic function.Comment: 9 pages, accepted to Arkiv f\"or Matemati
From thermal to excited-state quantum phase transitions ---the Dicke model
We study the thermodynamics of the full version of the Dicke model, including
all the possible values of the total angular momentum , with both
microcanonical and canonical ensembles. We focus on how the excited-state
quantum phase transition, which only appears in the microcanonical description
of the maximum angular momentum sector, , change to a standard thermal
phase transition when all the sectors are taken into account. We show that both
the thermal and the excited-state quantum phase transitions have the same
origin; in other words, that both are two faces of the same phenomenon. Despite
all the logarithmic singularities which characterize the excited-state quantum
phase transition are ruled out when all the -sectors are considered, the
critical energy (or temperature) still divides the spectrum in two regions: one
in which the parity symmetry can be broken, and another in which this symmetry
is always well defined.Comment: Submitted to PRE. Comments are welcome. V2: Updated to match
published versio
Behavioral modeling of PWL analog circuits using symbolic analysis
Behavioral models are used both for top-down design and for bottom-up verification. During top-down design, models are created that reflect the nominal behavior of the different analog functions, as well as the constraints imposed by the parasitics. In this scenario, the availability of symbolic modeling expressions enable designers to get insight on the circuits, and reduces the computational cost of design space exploration. During bottom-up verification, models are created that capture the topological and constitutive equations of the underlying devices into behavioral descriptions. In this scenario symbolic analysis is useful because it enables to automatically obtain these descriptions in the form of equations. This paper includes an example to illustrate the use of symbolic analysis for top-down design.Comisión Interministerial de Ciencia y Tecnología TIC97-058
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