102,270 research outputs found
Simple C*-algebras with locally finite decomposition rank
We introduce the notion of locally finite decomposition rank, a structural
property shared by many stably finite nuclear C*-algebras. The concept is
particularly relevant for Elliott's program to classify nuclear C*-algebras by
K-theory data. We study some of its properties and show that a simple unital
C*-algebra, which has locally finite decomposition rank, real rank zero and
which absorbs the Jiang-Su algebra Z tensorially, has tracial rank zero in the
sense of Lin. As a consequence, any such C*-algebra, if it additionally
satisfies the Universal Coefficients Theorem, is approximately homogeneous of
topological dimension at most 3. Our result in particular confirms the Elliott
conjecture for the class of simple unital Z-stable ASH algebras with real rank
zero. Moreover, it implies that simple unital Z-stable AH algebras with real
rank zero not only have slow dimension growth in the ASH sense, but even in the
AH sense.Comment: 30 pages, no figure
AC-Calorimetry at High Pressure and Low Temperature
Recent developments of the AC-calorimetric technique adapted for the needs of
high pressure experiments are discussed. A semi-quantitative measurement of the
specific heat with a Bridgman-type of pressure cell as well as a diamond anvil
cell is possible in the temperature range 0.1 K < T < 10 K. The pressure
transmitting medium used to ensure good pressure conditions determines to a
great extent via its thermal conductivity the operating frequency and thus the
accessible temperature range. Investigations with different pressure
transmitting media for T > 1.5 K reveal for solid He a cut-off frequency which
is considerably higher than for steatite. Experiments below 1 K and pressures
above 10 GPa clearly show that the pressure dependence of the linear
temperature coefficient of the specific heat can be measured. It is in
qualitative agreement to a related quantity obtained quasi-simultaneously by
electrical resistivity measurements on the same sample.Comment: 14 pages, 7 figures. The manuscript with high resoultion figures
(pdf-file, about 1Mb) can be downloaded from http://www.cpfs.mpg.de/~wilhelm
Occupational Structure of Yerwa in the 1920s
Yerwa is the last of the Borno capitals. Although established in the first decade of colonial administration, it cannot be compared with the many other towns like Fort Lamy, Jos, Kaduna, Niamey et al. which all developed about the same time. Colonial interference with the development of Yerwa appears restricted, mainly, to insistence upon wider roads than a Borno town otherwise would have featured and resettlement schemes, e.g. Mafoni, Ari Askeri. The following is based on the premise that as the town - despite time and political circumstances of its emergence - is a distinctive Borno town, also occupational diversification and structure are distinctively related to urban Borno culture
Amplitudes, Form Factors and the Dilatation Operator in SYM Theory
We study the form factor of a generic gauge-invariant local composite
operator in SYM theory. At tree level and for a minimal number
of external on-shell super fields, we find that the form factor precisely
yields the spin-chain picture of integrability in the language of scattering
amplitudes. Moreover, we compute the cut-constructible part of the one-loop
correction to this minimal form factor via generalised unitarity. From its UV
divergence, we obtain the complete one-loop dilatation operator of
SYM theory. Thus, we provide a field-theoretic derivation of a
relation between the one-loop dilatation operator and the four-point tree-level
amplitude which was observed earlier. We also comment on the implications of
our findings in the context of integrability.Comment: 39 pages, several figures, feynmp; v2: references added, typos
corrected; v3: references added, typos corrected, one explanation improved,
matches published versio
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