1,775 research outputs found
Target Zones and Exchange Rates: An Empirical Investigation
In this paper we develop an empirical model of exchange rates in a target zone. The model is general enough to nest most theoretical and empirical models in the existing literature. We find evidence of two types of jumps in exchange rates. Realignment jumps are those that are associated with the periodic realignments of the target zone and within-the-band jumps are those that can be accommodated within the current target zone. The exchange rate may jump outside the current target zone band, in the case of a realignment, but when no jump occurs the target zone is credible (there is zero probability of a realignment) and the exchange rate must stay within the band. We incorporate jumps, in general, by conditioning the distribution of exchange rate changes on a jump variable where the probability and size of a jump vary over time as a function of financial and macroeconomic variables. With this more general model, we revisit the empirical evidence from the European Monetary System regarding the conditional distribution of exchange rate changes, the credibility of the system, and the size of the foreign exchange risk premia. In contrast to some previous findings, we conclude that the FF/DM rate exhibits considerable non-linearities, realignments are predictable and the credibility of the system did not increase after 1987. Moreover, our model implies that the foreign exchange risk premium becomes large during speculative crises. A comparison with the Deutschemark/Dollar rate suggests that an explicit target zone does have a noticeable effect on the time-series behavior of exchange rates.
Current Exchanges for Reducible Higher Spin Multiplets and Gauge Fixing
We compute the current exchanges between triplets of higher spin fields which
describe reducible representations of the Poincare group. Through this
computation we can extract the propagator of the reducible higher spin fields
which compose the triplet. We show how to decompose the triplet fields into
irreducible HS fields which obey Fronsdal equations, and how to compute the
current-current interaction for the cubic couplings which appear in
ArXiv:0708.1399 [hep-th] using the decomposition into irreducible modes. We
compare this result with the same computation using a gauge fixed (Feynman)
version of the triplet Lagrangian which allows us to write very simple HS
propagators for the triplet fields.Comment: 26 pages, 1 table; v3 some clarifications and references added, typos
corrected. Published versio
Gauge fields and infinite chains of dualities
We show that the particle states of Maxwell's theory, in dimensions, can
be represented in an infinite number of ways by using different gauge fields.
Using this result we formulate the dynamics in terms of an infinite set of
duality relations which are first order in space-time derivatives. We derive a
similar result for the three form in eleven dimensions where such a possibility
was first observed in the context of E11. We also give an action formulation
for some of the gauge fields. In this paper we give a pedagogical account of
the Lorentz and gauge covariant formulation of the irreducible representations
of the Poincar\'e group, used previously in higher spin theories, as this plays
a key role in our constructions. It is clear that our results can be
generalised to any particle.Comment: 37 page
Detours and Paths: BRST Complexes and Worldline Formalism
We construct detour complexes from the BRST quantization of worldline
diffeomorphism invariant systems. This yields a method to efficiently extract
physical quantum field theories from particle models with first class
constraint algebras. As an example, we show how to obtain the Maxwell detour
complex by gauging N=2 supersymmetric quantum mechanics in curved space. Then
we concentrate on first class algebras belonging to a class of recently
introduced orthosymplectic quantum mechanical models and give generating
functions for detour complexes describing higher spins of arbitrary symmetry
types. The first quantized approach facilitates quantum calculations and we
employ it to compute the number of physical degrees of freedom associated to
the second quantized, field theoretical actions.Comment: 1+35 pages, 1 figure; typos corrected and references added, published
versio
A note on spin-s duality
Duality is investigated for higher spin (), free, massless, bosonic
gauge fields. We show how the dual formulations can be derived from a common
"parent", first-order action. This goes beyond most of the previous treatments
where higher-spin duality was investigated at the level of the equations of
motion only. In D=4 spacetime dimensions, the dual theories turn out to be
described by the same Pauli-Fierz (s=2) or Fronsdal () action (as it
is the case for spin 1). In the particular s=2 D=5 case, the Pauli-Fierz action
and the Curtright action are shown to be related through duality. A crucial
ingredient of the analysis is given by the first-order, gauge-like,
reformulation of higher spin theories due to Vasiliev.Comment: Minor corrections, reference adde
Higher spin interactions with scalar matter on constant curvature spacetimes: conserved current and cubic coupling generating functions
Cubic couplings between a complex scalar field and a tower of symmetric
tensor gauge fields of all ranks are investigated on any constant curvature
spacetime of dimension d>2. Following Noether's method, the gauge fields
interact with the scalar field via minimal coupling to the conserved currents.
A symmetric conserved current, bilinear in the scalar field and containing up
to r derivatives, is obtained for any rank r from its flat spacetime
counterpart in dimension d+1, via a radial dimensional reduction valid
precisely for the mass-square domain of unitarity in (anti) de Sitter spacetime
of dimension d. The infinite collection of conserved currents and cubic
vertices are summarized in a compact form by making use of generating functions
and of the Weyl/Wigner quantization on constant curvature spaces.Comment: 35+1 pages, v2: two references added, typos corrected, enlarged
discussions in Subsection 5.2 and in Conclusion, to appear in JHE
Higher spin fields from a worldline perspective
Higher spin fields in four dimensions, and more generally conformal fields in
arbitrary dimensions, can be described by spinning particle models with a
gauged SO(N) extended supergravity on the worldline. We consider here the
one-loop quantization of these models by studying the corresponding partition
function on the one-dimensional torus. After gauge fixing the supergravity
multiplet, the partition function reduces to an integral over the corresponding
moduli space which is computed using orthogonal polynomial techniques. We
obtain a compact formula which gives the number of physical degrees of freedom
for all N in all dimensions. As an aside we compute the physical degrees of
freedom of the SO(4) = SU(2)xSU(2) model with only a SU(2) factor gauged, which
has attracted some interest in the literature.Comment: 21 page
Spin three gauge theory revisited
We study the problem of consistent interactions for spin-3 gauge fields in
flat spacetime of arbitrary dimension n>3. Under the sole assumptions of
Poincar\'e and parity invariance, local and perturbative deformation of the
free theory, we determine all nontrivial consistent deformations of the abelian
gauge algebra and classify the corresponding deformations of the quadratic
action, at first order in the deformation parameter. We prove that all such
vertices are cubic, contain a total of either three or five derivatives and are
uniquely characterized by a rank-three constant tensor (an internal algebra
structure constant). The covariant cubic vertex containing three derivatives is
the vertex discovered by Berends, Burgers and van Dam, which however leads to
inconsistencies at second order in the deformation parameter. In dimensions n>4
and for a completely antisymmetric structure constant tensor, another covariant
cubic vertex exists, which contains five derivatives and passes the consistency
test where the previous vertex failed.Comment: LaTeX, 37 pages. References and comments added. Published versio
Unfolding Mixed-Symmetry Fields in AdS and the BMV Conjecture: I. General Formalism
We present some generalities of unfolded on-shell dynamics that are useful in
analysing the BMV conjecture for mixed-symmetry fields in constantly curved
backgrounds. In particular we classify the Lorentz-covariant Harish-Chandra
modules generated from primary Weyl tensors of arbitrary mass and shape, and in
backgrounds with general values of the cosmological constant. We also discuss
the unfolded notion of local degrees of freedom in theories with and without
gravity and with and without massive deformation parameters, using the language
of Weyl zero-form modules and their duals.Comment: Corrected typos, references added, two figures, some remarks and two
subsections added for clarit
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