2,215 research outputs found
Trotter product formulae for -automorphisms of quantum lattice systems
We consider the dynamics of an infinite quantum lattice
system that is generated by a local interaction. If the interaction decomposes
into a finite number of terms that are themselves local interactions, we show
that can be efficiently approximated by a product of
automorphisms, each of them being an alternating product generated by the
individual terms. For any integer , we construct a product formula (in the
spirit of Trotter) such that the approximation error scales as . Our
bounds hold in norm, pointwise for algebra elements that are sufficiently well
approximated by finite volume observables.Comment: Published in Annales Henri Poincar\'
Atom Interferometry in Space: Thermal Management and Magnetic Shielding
Atom interferometry is an exciting tool to probe fundamental physics. It is
considered especially apt to test the universality of free fall by using two
different sorts of atoms. The increasing sensitivity required for this kind of
experiment sets severe requirements on its environments, instrument control,
and systematic effects. This can partially be mitigated by going to space as
was proposed, for example, in the Spacetime Explorer and Quantum Equivalence
Principle Space Test (STE-QUEST) mission. However, the requirements on the
instrument are still very challenging. For example, the specifications of the
STE-QUEST mission imply that the Feshbach coils of the atom interferometer are
allowed to change their radius only by about 260 nm or 2.6E-4% due to thermal
expansion although they consume an average power of 22 W. Also Earth's magnetic
field has to be suppressed by a factor of 10E5. We show in this article that
with the right design such thermal and magnetic requirements can indeed be met
and that these are not an impediment for the exciting physics possible with
atom interferometers in space.Comment: v2: minor changes to agree with published version; 8 pages, 6 figure
Begreppet Början. En begreppsstyrd undersökning av det svenska ordförrÄdets förÀndring under 500 Är
Every concept has a lexicon. How this lexicon changes over time is the main focus of this article. The concept of Beginning is investigated over a period of 500 years. All words in the lexical field, both the living and the obsolete ones, are represented in the study. A method consisting of several steps is presented to reach the âprofileâ of the concept and to grasp the interaction of first elements (i.e. prefixes and adverbs) and roots over time
En databaserad begreppsordbok för den Àldre svenskan
Artikeln redovisar ett försök att utarbeta en databaserad, begreppsklassificerad ordbok för den Àldre och yngre nysvenskan. Ordboken bygger pÄ Rogets "Thesaurus" (och dess svenska motsvarighet: B ring) och Dahlgrens "Glossarium". Ett av huvudsyftena med ordboken Àr att den skall vara utgÄngspunkten i skapandet av en strukturell, synkronisk och historisk ordbok
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