371 research outputs found
Entanglement, Haag-duality and type properties of infinite quantum spin chains
We consider an infinite spin chain as a bipartite system consisting of the
left and right half-chain and analyze entanglement properties of pure states
with respect to this splitting. In this context we show that the amount of
entanglement contained in a given state is deeply related to the von Neumann
type of the observable algebras associated to the half-chains. Only the type I
case belongs to the usual entanglement theory which deals with density
operators on tensor product Hilbert spaces, and only in this situation
separable normal states exist. In all other cases the corresponding state is
infinitely entangled in the sense that one copy of the system in such a state
is sufficient to distill an infinite amount of maximally entangled qubit pairs.
We apply this results to the critical XY model and show that its unique ground
state provides a particular example for this type of entanglement.Comment: LaTeX2e, 34 pages, 1 figure (pstricks
Quantum group connections
The Ahtekar-Isham C*-algebra known from Loop Quantum Gravity is the algebra
of continuous functions on the space of (generalized) connections with a
compact structure Lie group. The algebra can be constructed by some inductive
techniques from the C*-algebra of continuous functions on the group and a
family of graphs embedded in the manifold underlying the connections. We
generalize the latter construction replacing the commutative C*-algebra of
continuous functions on the group by a non-commutative C*-algebra defining a
compact quantum group.Comment: 40 pages, LaTeX2e, minor mistakes corrected, abstract slightly
change
Endomorphisms and automorphisms of locally covariant quantum field theories
In the framework of locally covariant quantum field theory, a theory is
described as a functor from a category of spacetimes to a category of
*-algebras. It is proposed that the global gauge group of such a theory can be
identified as the group of automorphisms of the defining functor. Consequently,
multiplets of fields may be identified at the functorial level. It is shown
that locally covariant theories that obey standard assumptions in Minkowski
space, including energy compactness, have no proper endomorphisms (i.e., all
endomorphisms are automorphisms) and have a compact automorphism group.
Further, it is shown how the endomorphisms and automorphisms of a locally
covariant theory may, in principle, be classified in any single spacetime. As
an example, the endomorphisms and automorphisms of a system of finitely many
free scalar fields are completely classified.Comment: v2 45pp, expanded to include additional results; presentation
improved and an error corrected. To appear in Rev Math Phy
On localization and position operators in Moebius-covariant theories
Some years ago it was shown that, in some cases, a notion of locality can
arise from the group of symmetry enjoyed by the theory, thus in an intrinsic
way. In particular, when Moebius covariance is present, it is possible to
associate some particular transformations to the Tomita Takesaki modular
operator and conjugation of a specific interval of an abstract circle. In this
context we propose a way to define an operator representing the coordinate
conjugated with the modular transformations. Remarkably this coordinate turns
out to be compatible with the abstract notion of locality. Finally a concrete
example concerning a quantum particle on a line is also given.Comment: 19 pages, UTM 705, version to appear in RM
A generalized Fourier inversion theorem
In this work we define operator-valued Fourier transforms for suitable
integrable elements with respect to the Plancherel weight of a (not necessarily
Abelian) locally compact group. Our main result is a generalized version of the
Fourier inversion Theorem for strictly-unconditionally integrable Fourier
transforms. Our results generalize and improve those previously obtained by Ruy
Exel in the case of Abelian groups.Comment: 15 pages; some typos correcte
Localization via Automorphisms of the CARs. Local gauge invariance
The classical matter fields are sections of a vector bundle E with base
manifold M. The space L^2(E) of square integrable matter fields w.r.t. a
locally Lebesgue measure on M, has an important module action of C_b^\infty(M)
on it. This module action defines restriction maps and encodes the local
structure of the classical fields. For the quantum context, we show that this
module action defines an automorphism group on the algebra A, of the canonical
anticommutation relations on L^2(E), with which we can perform the analogous
localization. That is, the net structure of the CAR, A, w.r.t. appropriate
subsets of M can be obtained simply from the invariance algebras of appropriate
subgroups. We also identify the quantum analogues of restriction maps. As a
corollary, we prove a well-known "folk theorem," that the algebra A contains
only trivial gauge invariant observables w.r.t. a local gauge group acting on
E.Comment: 15 page
Information Transfer Implies State Collapse
We attempt to clarify certain puzzles concerning state collapse and
decoherence. In open quantum systems decoherence is shown to be a necessary
consequence of the transfer of information to the outside; we prove an upper
bound for the amount of coherence which can survive such a transfer. We claim
that in large closed systems decoherence has never been observed, but we will
show that it is usually harmless to assume its occurrence. An independent
postulate of state collapse over and above Schroedinger's equation and the
probability interpretation of quantum states, is shown to be redundant.Comment: 13 page
On the Grothendieck Theorem for jointly completely bounded bilinear forms
We show how the proof of the Grothendieck Theorem for jointly completely
bounded bilinear forms on C*-algebras by Haagerup and Musat can be modified in
such a way that the method of proof is essentially C*-algebraic. To this
purpose, we use Cuntz algebras rather than type III factors. Furthermore, we
show that the best constant in Blecher's inequality is strictly greater than
one.Comment: 9 pages, minor change
Hubungan Kelelahan Kerja dan Stress Kerja dengan Kecelakaan Kerja Tertusuk Jarum Jahit pada Pekerja Bagian Garmen di PT. Danliris Sukoharjo
Latar Belakang : Meningkatnya penggunaan teknologi di berbagai sektor usaha
dapat pula mengakibatkan semakin tinggi resiko terjadinya kecelakaan kerja dan
penyakit akibat kerja atau penyakit yang berhubungan dengan pekerjaan yang
mengancam keselamatan, kesehatan dan kesejahteraan tenaga kerja. Dalam tiga tahun
terakhir di PT. Danliris Sukoharjo, terjadi 38 kasus kecelakaan kerja tertusuk jarum
jahit. Tujuan penelitian ini untuk mengetahui apakah kelelahan kerja dan stress kerja
mempunyai hubungan dengan terjadinya kecelakaan kerja tertusuk jarum jahit.
Metode : Penelitian ini menggunakan metode observasional analitik dengan
rancangan cross sectional. Sampel diambil dengan metode simple random sampling
sebanyak 200 pekerja bagian garmen. Pengumpulan data dilakukan dengan pengisian
kuesioner kelelahan kerja dan stress kerja serta kecelakaan kerja tertusuk jarum jahit
dilakukan dengan observasional. Pengolahan dan analisa data menggunakan uji
statistik chi square dengan uji alterrnatif fisher.
Hasil : Hasil penelitian ini menunjukkan tidak ada hubungan antara kelelahan kerja
dengan terjadinya kecelakaan kerja tertusuk jarum jahit (p value 0.619) dan tidak ada
hubungan antara stress kerja dengan kecelakaan kerja tertusuk jarum jahit (p value
0.137).
Kesimpulan : Kelelahan kerja dan stress kerja tidak mempunyai hubungan dengan
terjadinya kecelakaan kerja tertusuk jarum jahit.
Kata Kunci : Kelelahan Kerja, Stress Kerja, Kecelakaan Kerj
Tsirelson's problem and Kirchberg's conjecture
Tsirelson's problem asks whether the set of nonlocal quantum correlations
with a tensor product structure for the Hilbert space coincides with the one
where only commutativity between observables located at different sites is
assumed. Here it is shown that Kirchberg's QWEP conjecture on tensor products
of C*-algebras would imply a positive answer to this question for all bipartite
scenarios. This remains true also if one considers not only spatial
correlations, but also spatiotemporal correlations, where each party is allowed
to apply their measurements in temporal succession; we provide an example of a
state together with observables such that ordinary spatial correlations are
local, while the spatiotemporal correlations reveal nonlocality. Moreover, we
find an extended version of Tsirelson's problem which, for each nontrivial Bell
scenario, is equivalent to the QWEP conjecture. This extended version can be
conveniently formulated in terms of steering the system of a third party.
Finally, a comprehensive mathematical appendix offers background material on
complete positivity, tensor products of C*-algebras, group C*-algebras, and
some simple reformulations of the QWEP conjecture.Comment: 57 pages, to appear in Rev. Math. Phy
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