4,987 research outputs found
A Riccati type PDE for light-front higher helicity vertices
This paper is based on a curious observation about an equation related to the
tracelessness constraints of higher spin gauge fields. The equation also occurs
in the theory of continuous spin representations of the Poincar\'e group.
Expressed in an oscillator basis for the higher spin fields, the equation
becomes a non-linear partial differential operator of the Riccati type acting
on the vertex functions. The consequences of the equation for the cubic vertex
is investigated in the light-front formulation of higher spin theory. The
classical vertex is completely fixed but there is room for off-shell quantum
corrections.Comment: 27 pages. Updated to published versio
Counterterms in Gravity in the Light-Front Formulation and a D=2 Conformal-like Symmetry in Gravity
In this paper we discuss gravity in the light-front formulation (light-cone
gauge) and show how possible counterterms arise. We find that Poincare
invariance is not enough to find the three-point counterterms uniquely.
Higher-spin fields can intrude and mimic three-point higher derivative gravity
terms. To select the correct term we have to use the remaining
reparametrization invariance that exists after the gauge choice. We finally
sketch how the corresponding programme for N=8 Supergravity should work.Comment: 26 pages, references added, published versio
Population-only decay map for n-qubit n-partite inseparability detection
We introduce a new positive linear map for a single qubit. This map is a
decay only in populations of a single-qubit density operator. It is shown that
an n-fold product of this map may be used for a detection of n-partite
inseparability of an n-qubit density operator (i.e., detection of impossibility
of representing a density operator in the form of a convex combination of
products of density operators of individual qubits). This product map is also
investigated in relation to a variant of the entanglement detection method
mentioned by Laskowski and Zukowski.Comment: 5 pages, 1 figure, RevTex4, v2 minor grammatical changes, typos
correcte
Constructing entanglement witnesses for infinite-dimensional systems
It is shown that, every entangled state in an infinite-dimensional composite
system has a simple entanglement witness of the form with
a nonnegative number and a finite rank self-adjoint operator. We also
provide two methods of constructing entanglement witness and apply them to
obtain some entangled states that cannot be detected by the PPT criterion and
the realignment criterion.Comment: 15 page
Second order statistics of NLOS indoor MIMO channels based on 5.2 GHz measurements
This document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available
Local and global statistical distances are equivalent on pure states
The statistical distance between pure quantum states is obtained by finding a
measurement that is optimal in a sense defined by Wootters. As such, one may
expect that the statistical distance will turn out to be different if the set
of possible measurements is restricted in some way. It nonetheless turns out
that if the restriction is to local operations and classical communication
(LOCC) on any multipartite system, then the statistical distance is the same as
it is without restriction, being equal to the angle between the states in
Hilbert space.Comment: 5 pages, comments welcom
Towards Unifying Structures in Higher Spin Gauge Symmetry
This article is expository in nature, outlining some of the many still
incompletely understood features of higher spin field theory. We are mainly
considering higher spin gauge fields in their own right as free-standing
theoretical constructs and not circumstances where they occur as part of
another system. Considering the problem of introducing interactions among
higher spin gauge fields, there has historically been two broad avenues of
approach. One approach entails gauging a non-Abelian global symmetry algebra,
in the process making it local. The other approach entails deforming an already
local but Abelian gauge algebra, in the process making it non-Abelian. In cases
where both avenues have been explored, such as for spin 1 and 2 gauge fields,
the results agree (barring conceptual and technical issues) with Yang-Mills
theory and Einstein gravity. In the case of an infinite tower of higher spin
gauge fields, the first approach has been thoroughly developed and explored by
M. Vasiliev, whereas the second approach, after having lain dormant for a long
time, has received new attention by several authors lately. In the present
paper we briefly review some aspects of the history of higher spin gauge fields
as a backdrop to an attempt at comparing the gauging vs. deforming approaches.
A common unifying structure of strongly homotopy Lie algebras underlying both
approaches will be discussed. The modern deformation approach, using BRST-BV
methods, will be described as far as it is developed at the present time. The
first steps of a formulation in the categorical language of operads will be
outlined. A few aspects of the subject that seems not to have been thoroughly
investigated are pointed out.Comment: This is a contribution to the Proc. of the Seventh International
Conference ''Symmetry in Nonlinear Mathematical Physics'' (June 24-30, 2007,
Kyiv, Ukraine), published in SIGMA (Symmetry, Integrability and Geometry:
Methods and Applications) at http://www.emis.de/journals/SIGMA
- …