18,583 research outputs found
Novel Symmetries in Christ-Lee Model
We demonstrate that the gauge-fixed Lagrangian of the Christ-Lee model
respects four fermionic symmetries, namely; (anti-)BRST symmetries,
(anti-)co-BRST symmetries within the framework of BRST formalism. The
appropriate anticommutators amongst the fermionic symmetries lead to a unique
bosonic symmetry. It turns out that the algebra obeyed by the symmetry
transformations (and their corresponding conserved charges) is reminiscent of
the algebra satisfied by the de Rham cohomological operators of differential
geometry. We also provide the physical realizations of the cohomological
operators in terms of the symmetry properties. Thus, the present model provides
a simple model for the Hodge theory.Comment: LaTeX File, 12 Pages, Text Modified, Typos Fixed, Refences Added, No
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Some Characterizations of a Normal Subgroup of a Group
Let G be a group and H be a subgroup of G which is either finite or of finite
index in G. In this note, we give some characterizations for normality of H in
G. As a consequence we get a very short and elementary proof of the Main
Theorem of [5], which avoids the use of the classification of finite simple
group
Beyond the Goldenberg-Vaidman protocol: Secure and efficient quantum communication using arbitrary, orthogonal, multi-particle quantum states
It is shown that maximally efficient protocols for secure direct quantum
communications can be constructed using any arbitrary orthogonal basis. This
establishes that no set of quantum states (e.g. GHZ states, W states, Brown
states or Cluster states) has an advantage over the others, barring the
relative difficulty in physical implementation. The work provides a wide choice
of states for experimental realization of direct secure quantum communication
protocols. We have also shown that this protocol can be generalized to a
completely orthogonal state based protocol of Goldenberg-Vaidman (GV) type. The
security of these protocols essentially arises from duality and monogamy of
entanglement. This stands in contrast to protocols that employ non-orthogonal
states, like Bennett-Brassard 1984 (BB84), where the security essentially comes
from non-commutativity in the observable algebra.Comment: 7 pages, no figur
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