6,466 research outputs found
Geometry versus Entanglement in Resonating Valence Bond Liquids
We investigate the behavior of bipartite as well as genuine multipartite
entanglement of a resonating valence bond state on a ladder. We show that the
system possesses significant amounts of bipartite entanglement in the steps of
the ladder while no substantial bipartite entanglement is present in the rails.
Genuine multipartite entanglement present in the system is negligible. The
results are in stark contrast with the entanglement properties of the same
state on isotropic lattices in two and higher dimensions, indicating that the
geometry of the lattice can have important implications on the quality of
quantum information and other tasks that can be performed by using multiparty
states on that lattice.Comment: 6 pages, 8 figures, RevTeX
Fundamental Strings in Open String Theory at the Tachyonic Vacuum
We show that the world-volume theory on a D-p-brane at the tachyonic vacuum
has solitonic string solutions whose dynamics is governed by the Nambu-Goto
action of a string moving in (25+1) dimensional space-time. This provides
strong evidence for the conjecture that at this vacuum the full (25+1)
dimensional Poincare invariance is restored. We also use this result to argue
that the open string field theory at the tachyonic vacuum must contain closed
string excitations.Comment: LaTeX file, 16 pages, references and clarification adde
Density Matrix Recursion Method: Genuine Multisite Entanglement Distinguishes Odd from Even Quantum Heisenberg Ladders
We introduce an analytical iterative method, the density matrix recursion
method, to generate arbitrary reduced density matrices of superpositions of
short-range dimer coverings on periodic or non-periodic quantum spin-1/2 ladder
lattices, with an arbitrary number of legs. The method can be used to calculate
bipartite as well as multipartite physical properties, including bipartite and
multi-partite entanglement. We apply this technique to distinguish between
even- and odd-legged ladders. Specifically, we show that while genuine
multi-partite entanglement decreases with increasing system size for the
even-legged ladder states, it does the opposite for odd-legged ones.Comment: 13 pages, 3 figures, iopart.cls, final edited versio
The Mass, Normalization and Late Time behavior of the Tachyon Field
We study the dynamics of the tachyon field . We derive the mass of the
tachyon as the pole of the propagator which does not coincide with the standard
mass given in the literature in terms of the second derivative of or
. We determine the transformation of the tachyon in order to have a
canonical scalar field . This transformation reduces to the one obtained
for small but it is also valid for large values of . This is
specially interesting for the study of dark energy where . We
also show that the normalized tachyon field is constrained to the
interval where are zeros of the original
potential . This results shows that the field does not know of the
unboundedness of , as suggested for bosonic open string tachyons. Finally
we study the late time behavior of tachyon field using the L'H\^{o}pital rule.Comment: 9 pages, 10 figure
Statistics of leading digits leads to unification of quantum correlations
We show that the frequency distribution of the first significant digits of
the numbers in the data sets generated from a large class of measures of
quantum correlations, which are either entanglement measures, or belong to the
information-theoretic paradigm, exhibit a universal behaviour. In particular,
for Haar uniformly simulated arbitrary two-qubit states, we find that the
first-digit distribution corresponding to a collection of chosen computable
quantum correlation quantifiers tend to follow the first-digit law, known as
the Benford's law, when the rank of the states increases. Considering a
two-qubit state which is obtained from a system governed by paradigmatic spin
Hamiltonians, namely, the XY model in a transverse field, and the XXZ model, we
show that entanglement as well as information theoretic measures violate the
Benford's law. We quantitatively discuss the violation of the Benford's law by
using a violation parameter, and demonstrate that the violation parameter can
signal quantum phase transitions occurring in these models. We also comment on
the universality of the statistics of first significant digits corresponding to
appropriate measures of quantum correlations in the case of multipartite
systems as well as systems in higher dimensions.Comment: v1: 11 pages, 5 figures, 2 tables; v2: 11 pages, 6 figures, 2 tables,
new results added, extended version of the published pape
Decay of Unstable D-branes with Electric Field
Using the techniques of two dimensional conformal field theory we construct
time dependent classical solutions in open string theory describing the decay
of an unstable D-brane in the presence of background electric field, and
explicitly evaluate the time dependence of the energy momentum tensor and the
fundamental string charge density associated with this solution. The final
decay product can be interpreted as a combination of stretched fundamental
strings and tachyon matter.Comment: 35 pages, LaTe
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