6,733 research outputs found
Spin-statistics transmutation in relativistic quantum field theories of dyons
We analyse spin and statistics of quantum dyon fields, i.e. fields carrying
both electric and magnetic charge, in 3+1 space-time dimensions. It has been
shown long time ago that, at the quantum mechanical level, a composite dyon
made out of a magnetic pole of charge g and a particle of electric charge e
possesses half-integral spin and fermionic statistics, if the constituents are
bosons and the Dirac quantization condition holds, with n odd. This
phenomenon is called spin-statistics transmutation. We show that the same
phenomenon occurs at the quantum field theory level for an elementary dyon.
This analysis requires the construction of gauge invariant charged dyon fields.
Dirac's proposal for such fields, relying on a Coulomb-like photon cloud, leads
to quantum correlators exhibiting an unphysical dependence on the Dirac-string.
Recently Froehlich and Marchetti proposed a recipe for charged dyon fields,
based on a sum over Mandelstam-strings, which overcomes this problem. Using
this recipe we derive explicit expressions for the quantum field theory
correlators and we provide a proof of the occurrence of spin-statistics
transmutation. The proof reduces to a computation of the self-linking numbers
of dyon worldlines and Mandelstam strings, projected on a fixed time
three-space. Dyon composites are also analysed. The transmutation discussed in
this paper bares some analogy with the appearance of anomalous spin and
statistics for particles or vortices in Chern-Simons theories in 2+1
dimensions. However, peculiar features appear in 3+1 dimensions e.g. in the
spin addition rule.Comment: 32 pages, LaTeX, no figure
Interacting branes, dual branes, and dyonic branes: a unifying lagrangian approach in D dimensions
This paper presents a general covariant lagrangian framework for the dynamics
of a system of closed n-branes and dual (D-n-4)-branes in D dimensions,
interacting with a dynamical (n+1)-form gauge potential. The framework proves
sufficiently general to include also a coupling of the branes to (the bosonic
sector of) a dynamical supergravity theory. We provide a manifestly
Lorentz-invariant and S-duality symmetric Lagrangian, involving the (n+1)-form
gauge potential and its dual (D-n-3)-form gauge potential in a symmetric way.
The corresponding action depends on generalized Dirac-strings. The requirement
of string-independence of the action leads to Dirac-Schwinger quantization
conditions for the charges of branes and dual branes, but produces also
additional constraints on the possible interactions. It turns out that a system
of interacting dyonic branes admits two quantum mechanically inequivalent
formulations, involving inequivalent quantization conditions. Asymmetric
formulations involving only a single vector potential are also given. For the
special cases of dyonic branes in even dimensions known results are easily
recovered. As a relevant application of the method we write an effective action
which implements the inflow anomaly cancellation mechanism for interacting
heterotic strings and five-branes in D=10. A consistent realization of this
mechanism requires, in fact, dynamical p-form potentials and a systematic
introduction of Dirac-strings.Comment: 36 pages, LaTeX, no figure
On the existence of self-similar spherically symmetric wave maps coupled to gravity
We present a detailed analytical study of spherically symmetric self-similar
solutions in the SU(2) sigma model coupled to gravity. Using a shooting
argument we prove that there is a countable family of solutions which are
analytic inside the past self-similarity horizon. In addition, we show that for
sufficiently small values of the coupling constant these solutions possess a
regular future self-similarity horizon and thus are examples of naked
singularities. One of the solutions constructed here has been recently found as
the critical solution at the threshold of black hole formation.Comment: 15 pages, LaTe
On the equivalence of two deformation schemes in quantum field theory
Two recent deformation schemes for quantum field theories on the
two-dimensional Minkowski space, making use of deformed field operators and
Longo-Witten endomorphisms, respectively, are shown to be equivalent.Comment: 14 pages, no figure. The final version is available under Open
Access. CC-B
Delay-Exponent of Bilayer Anytime Code
In this paper, we study the design and the delay-exponent of anytime codes
over a three terminal relay network. We propose a bilayer anytime code based on
anytime spatially coupled low-density parity-check (LDPC) codes and investigate
the anytime characteristics through density evolution analysis. By using
mathematical induction technique, we find analytical expressions of the
delay-exponent for the proposed code. Through comparison, we show that the
analytical delay-exponent has a close match with the delay-exponent obtained
from numerical results.Comment: Accepted for presentation in ITW-2014. 5 Pages, 3 Figure
Finite Length Analysis of LDPC Codes
In this paper, we study the performance of finite-length LDPC codes in the
waterfall region. We propose an algorithm to predict the error performance of
finite-length LDPC codes over various binary memoryless channels. Through
numerical results, we find that our technique gives better performance
prediction compared to existing techniques.Comment: Submitted to WCNC 201
Radiation reaction and four-momentum conservation for point-like dyons
We construct for a system of point-like dyons a conserved energy-momentum
tensor entailing finite momentum integrals, that takes the radiation reaction
into account.Comment: 12 pages, no figure
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