5,565 research outputs found
Monetary and Fiscal Policies in an Open Economy
The central theme of this paper is that international linkages between national economies influence, in fundamentally important ways, the effectiveness and proper conduct of national macroeconomic policies. Specifically, our purpose is to summarize the implications for the conduct of macroeconomic policies in open economies of both the traditional approach to open economy macroeconomics (as developed largely by James Meade, Robert Mundell, and J. Marcus Fleming) and of more recent developments. Our discussion is organized around three key linkages between national economies: through commodity trade; through capital mobility; and through exchange of national monies. These linkages have important implications concerning the effects of macroeconomic policies in open economies that differ from the effects of such policies in closed economies. Recent developments in the theory of macroeconomic policy have established conditions for the effectiveness of policies in influencing output and employment which emphasize the distinction between anticipated and unanticipated policy actions, the importance of incomplete information, and the consequences of contracts that fix nominal wages and prices over finite intervals. In this paper, we shall not analyze how these conditions are modified in an open economy. However, since our concern is with macro-economic policy, a principal objective of which is to influence output and employment, we shall assume that requisite conditions for such influence are satisfied.
Dressing Symmetries of Holomorphic BF Theories
We consider holomorphic BF theories, their solutions and symmetries. The
equivalence of Cech and Dolbeault descriptions of holomorphic bundles is used
to develop a method for calculating hidden (nonlocal) symmetries of holomorphic
BF theories. A special cohomological symmetry group and its action on the
solution space are described.Comment: 14 pages, LaTeX2
Constructing quantum vertex algebras
This is a sequel to \cite{li-qva}. In this paper, we focus on the
construction of quantum vertex algebras over \C, whose notion was formulated
in \cite{li-qva} with Etingof and Kazhdan's notion of quantum vertex operator
algebra (over \C[[h]]) as one of the main motivations. As one of the main
steps in constructing quantum vertex algebras, we prove that every
countable-dimensional nonlocal (namely noncommutative) vertex algebra over
\C, which either is irreducible or has a basis of PBW type, is nondegenerate
in the sense of Etingof and Kazhdan. Using this result, we establish the
nondegeneracy of better known vertex operator algebras and some nonlocal vertex
algebras. We then construct a family of quantum vertex algebras closely related
to Zamolodchikov-Faddeev algebras.Comment: 37 page
Pulse propagation in discrete systems of coupled excitable cells
Propagation of pulses in myelinated fibers may be described by appropriate
solutions of spatially discrete FitzHugh-Nagumo systems. In these systems,
propagation failure may occur if either the coupling between nodes is not
strong enough or the recovery is too fast. We give an asymptotic construction
of pulses for spatially discrete FitzHugh-Nagumo systems which agrees well with
numerical simulations and discuss evolution of initial data into pulses and
pulse generation at a boundary. Formulas for the speed and length of pulses are
also obtained.Comment: 16 pages, 10 figures, to appear in SIAM J. Appl. Mat
Dynamical transitions in incommensurate systems
In the dynamics of the undamped Frenkel-Kontorova model with kinetic terms,
we find a transition between two regimes, a floating incommensurate and a
pinned incommensurate phase. This behavior is compared to the static version of
the model. A remarkable difference is that, while in the static case the two
regimes are separated by a single transition (the Aubry transition), in the
dynamical case the transition is characterized by a critical region, in which
different phenomena take place at different times. In this paper, the
generalized angular momentum we have previously introduced, and the dynamical
modulation function are used to begin a characterization of this critical
region. We further elucidate the relation between these two quantities, and
present preliminary results about the order of the dynamical transition.Comment: 7 pages, 6 figures, file 'epl.cls' necessary for compilation
provided; subm. to Europhysics Letter
On Representations of Conformal Field Theories and the Construction of Orbifolds
We consider representations of meromorphic bosonic chiral conformal field
theories, and demonstrate that such a representation is completely specified by
a state within the theory. The necessary and sufficient conditions upon this
state are derived, and, because of their form, we show that we may extend the
representation to a representation of a suitable larger conformal field theory.
In particular, we apply this procedure to the lattice (FKS) conformal field
theories, and deduce that Dong's proof of the uniqueness of the twisted
representation for the reflection-twisted projection of the Leech lattice
conformal field theory generalises to an arbitrary even (self-dual) lattice. As
a consequence, we see that the reflection-twisted lattice theories of Dolan et
al are truly self-dual, extending the analogies with the theories of lattices
and codes which were being pursued. Some comments are also made on the general
concept of the definition of an orbifold of a conformal field theory in
relation to this point of view.Comment: 11 pages, LaTeX. Updated references and added preprint n
Effective actions at finite temperature
This is a more detailed version of our recent paper where we proposed, from
first principles, a direct method for evaluating the exact fermion propagator
in the presence of a general background field at finite temperature. This can,
in turn, be used to determine the finite temperature effective action for the
system. As applications, we discuss the complete one loop finite temperature
effective actions for 0+1 dimensional QED as well as for the Schwinger model in
detail. These effective actions, which are derived in the real time (closed
time path) formalism, generate systematically all the Feynman amplitudes
calculated in thermal perturbation theory and also show that the retarded
(advanced) amplitudes vanish in these theories. Various other aspects of the
problem are also discussed in detail.Comment: 9 pages, revtex, 1 figure, references adde
Mutually Penetrating Motion of Self-Organized 2D Patterns of Soliton-Like Structures
Results of numerical simulations of a recently derived most general
dissipative-dispersive PDE describing evolution of a film flowing down an
inclined plane are presented. They indicate that a novel complex type of
spatiotemporal patterns can exist for strange attractors of nonequilibrium
systems. It is suggested that real-life experiments satisfying the validity
conditions of the theory are possible: the required sufficiently viscous
liquids are readily available.Comment: minor corrections, 4 pages, LaTeX, 6 figures, mpeg simulations
available upon or reques
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