93 research outputs found
A class of Bell diagonal states and entanglement witnesses
We analyze special class of bipartite states - so called Bell diagonal
states. In particular we provide new examples of bound entangled Bell diagonal
states and construct the class of entanglement witnesses diagonal in the magic
basis.Comment: 17 page
A class of commutative dynamics of open quantum systems
We analyze a class of dynamics of open quantum systems which is governed by
the dynamical map mutually commuting at different times. Such evolution may be
effectively described via spectral analysis of the corresponding time dependent
generators. We consider both Markovian and non-Markovian cases.Comment: 22 page
Bounds on the entanglement of two-qutrit systems from fixed marginals
We discuss the problem of characterizing upper bounds on entanglement in a bipartite quantum system when only the reduced density matrices (marginals) are known. In particular, starting from the known two-qubit case, we propose a family of candidates for maximally entangled mixed states with respect to fixed marginals for two qutrits. These states are extremal in the convex set of two-qutrit states with fixed marginals. Moreover, it is shown that they are always quasidistillable. As a by-product we prove that any maximally correlated state that is quasidistillable must be pure. Our observations for two qutrits are supported by numerical analysis
Dynamics of the Born-Infeld dyons
The approach to the dynamics of a charged particle in the Born-Infeld
nonlinear electrodynamics developed in [Phys. Lett. A 240 (1998) 8] is
generalized to include a Born-Infeld dyon. Both Hamiltonian and Lagrangian
structures of many dyons interacting with nonlinear electromagnetism are
constructed. All results are manifestly duality invariant.Comment: 11 pages, LATE
Characterizing entanglement with geometric entanglement witnesses
We show how to detect entangled, bound entangled, and separable bipartite
quantum states of arbitrary dimension and mixedness using geometric
entanglement witnesses. These witnesses are constructed using properties of the
Hilbert-Schmidt geometry and can be shifted along parameterized lines. The
involved conditions are simplified using Bloch decompositions of operators and
states. As an example we determine the three different types of states for a
family of two-qutrit states that is part of the "magic simplex", i.e. the set
of Bell-state mixtures of arbitrary dimension.Comment: 19 pages, 4 figures, some typos and notational errors corrected. To
be published in J. Phys. A: Math. Theo
Canonical formalism for the Born-Infeld particle
In the previous paper (hep-th/9712161) it was shown that the nonlinear
Born-Infeld field equations supplemented by the "dynamical condition" (certain
boundary condition for the field along the particle's trajectory) define
perfectly deterministic theory, i.e. particle's trajectory is determined
without any equations of motion. In the present paper we show that this theory
possesses mathematically consistent Lagrangian and Hamiltonian formulations.
Moreover, it turns out that the "dynamical condition" is already present in the
definition of the physical phase space and, therefore, it is a basic element of
the theory.Comment: 14 pages, LATE
Coulomb's law modification in nonlinear and in noncommutative electrodynamics
We study the lowest-order modifications of the static potential for
Born-Infeld electrodynamics and for the -expanded version of the
noncommutative U(1) gauge theory, within the framework of the gauge-invariant
but path-dependent variables formalism. The calculation shows a long-range
correction (-type) to the Coulomb potential in Born-Infeld
electrodynamics. However, the Coulomb nature of the potential (to order )
is preserved in noncommutative electrodynamics.Comment: 14 pages, 1 figur
UV/IR duality in noncommutative quantum field theory
We review the construction of renormalizable noncommutative euclidean
phi(4)-theories based on the UV/IR duality covariant modification of the
standard field theory, and how the formalism can be extended to scalar field
theories defined on noncommutative Minkowski space.Comment: 12 pages; v2: minor corrections, note and references added;
Contribution to proceedings of the 2nd School on "Quantum Gravity and Quantum
Geometry" session of the 9th Hellenic School on Elementary Particle Physics
and Gravity, Corfu, Greece, September 13-20 2009. To be published in General
Relativity and Gravitatio
The Newman-Janis Algorithm, Rotating Solutions and Einstein-Born-Infeld Black Holes
A new metric is obtained by applying a complex coordinate trans- formation to
the static metric of the self-gravitating Born-Infeld monopole. The behaviour
of the new metric is typical of a rotating charged source, but this source is
not a spherically symmetric Born-Infeld monopole with rotation. We show that
the structure of the energy-momentum tensor obtained with this new metric does
not correspond to the typical structure of the energy momentum tensor of
Einstein-Born-Infeld theory induced by a rotating spherically symmetric source.
This also show, that the complex coordinate transformations have the
interpretation given by Newman and Janis only in space-time solutions with
linear sources
Quantum anomaly and geometric phase; their basic differences
It is sometimes stated in the literature that the quantum anomaly is regarded
as an example of the geometric phase. Though there is some superficial
similarity between these two notions, we here show that the differences bewteen
these two notions are more profound and fundamental. As an explicit example, we
analyze in detail a quantum mechanical model proposed by M. Stone, which is
supposed to show the above connection. We show that the geometric term in the
model, which is topologically trivial for any finite time interval ,
corresponds to the so-called ``normal naive term'' in field theory and has
nothing to do with the anomaly-induced Wess-Zumino term. In the fundamental
level, the difference between the two notions is stated as follows: The
topology of gauge fields leads to level crossing in the fermionic sector in the
case of chiral anomaly and the {\em failure} of the adiabatic approximation is
essential in the analysis, whereas the (potential) level crossing in the matter
sector leads to the topology of the Berry phase only when the precise adiabatic
approximation holds.Comment: 28 pages. The last sentence in Abstract has been changed, the last
paragraph in Section 1 has been re-written, and the latter half of Discussion
has been replaced by new materials. New Conclusion to summarize the analysis
has been added. This new version is to be published in Phys. Rev.
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