168 research outputs found
Modified mixed Tsirelson spaces
We study the modified and boundedly modified mixed Tsirelson spaces
and respectively, defined by a subsequence
of the sequence of Schreier families . These
are reflexive asymptotic spaces with an unconditio- nal basis
having the property that every sequence of
normalized disjointly supported vectors contained in is equivalent to the basis of . We show
that if then the space and its modified variations are totally incomparable by
proving that is finitely disjointly representable in every block subspace
of . Next, we present an example of
a boundedly modified mixed Tsirelson space which is arbitrarily
distortable. Finally, we construct a variation of the space which
is hereditarily indecomposable
Finite size effects on measures of critical exponents in d=3 O(N) models
We study the critical properties of three-dimensional O(N) models, for
N=2,3,4. Parameterizing the leading corrections-to-scaling for the
exponent, we obtain a reliable infinite volume extrapolation, incompatible with
previous Monte Carlo values, but in agreement with -expansions. We
also measure the critical exponent related with the tensorial magnetization as
well as the exponents and critical couplings.Comment: 12 pages, 2 postscript figure
A PMT-Block test bench
The front-end electronics of the ATLAS hadronic calorimeter (Tile Cal) is
housed in a unit, called {\it PMT-Block}. The PMT-Block is a compact instrument
comprising a light mixer, a PMT together with its divider and a {\it 3-in-1}
card, which provides shaping, amplification and integration for the signals.
This instrument needs to be qualified before being assembled on the detector. A
PMT-Block test bench has been developed for this purpose. This test bench is a
system which allows fast, albeit accurate enough, measurements of the main
properties of a complete PMT-Block. The system, both hardware and software, and
the protocol used for the PMT-Blocks characterisation are described in detail
in this report. The results obtained in the test of about 10000 PMT-Blocks
needed for the instrumentation of the ATLAS (LHC-CERN) hadronic Tile
Calorimeter are also reported.Comment: 23 pages, 10 figure
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