922 research outputs found
Modular Groups of Quantum Fields in Thermal States
For a quantum field in a thermal equilibrium state we discuss the group
generated by time translations and the modular action associated with an
algebra invariant under half-sided translations. The modular flows associated
with the algebras of the forward light cone and a space-like wedge admit a
simple geometric description in two dimensional models that factorize in
light-cone coordinates. At large distances from the domain boundary compared to
the inverse temperature the flow pattern is essentially the same as time
translations, whereas the zero temperature results are approximately reproduced
close to the edge of the wedge and the apex of the cone. Associated with each
domain there is also a one parameter group with a positive generator, for which
the thermal state is a ground state. Formally, this may be regarded as a
certain converse of the Unruh-effect.Comment: 28 pages, 4 figure
Charged sectors, spin and statistics in quantum field theory on curved spacetimes
The first part of this paper extends the Doplicher-Haag-Roberts theory of
superselection sectors to quantum field theory on arbitrary globally hyperbolic
spacetimes. The statistics of a superselection sector may be defined as in flat
spacetime and each charge has a conjugate charge when the spacetime possesses
non-compact Cauchy surfaces. In this case, the field net and the gauge group
can be constructed as in Minkowski spacetime.
The second part of this paper derives spin-statistics theorems on spacetimes
with appropriate symmetries. Two situations are considered: First, if the
spacetime has a bifurcate Killing horizon, as is the case in the presence of
black holes, then restricting the observables to the Killing horizon together
with "modular covariance" for the Killing flow yields a conformally covariant
quantum field theory on the circle and a conformal spin-statistics theorem for
charged sectors localizable on the Killing horizon. Secondly, if the spacetime
has a rotation and PT symmetry like the Schwarzschild-Kruskal black holes,
"geometric modular action" of the rotational symmetry leads to a
spin-statistics theorem for charged covariant sectors where the spin is defined
via the SU(2)-covering of the spatial rotation group SO(3).Comment: latex2e, 73 page
Trypsin Inhibitor. VII. Comparative Nutritive Value of Raw and Heated Soybean Meal for Poults
I. The trypsin inhibitor contained in one-half of a lot of soybean meal was destroyed by autoclaving at 15 pounds for 20 minutes. 2. This portion of the meal when fed at a level of 24 per cent to newly hatched poults gave a significantly greater gain in five weeks than did an equal amount of meal in which the inhibitor had not been destroyed. 3. The difference in growth is attributed to the destruction of the trypsin inhibitor
The Utilization of Food Elements by Growing Chicks. XIII. The Effect of Additions of Dehydrated Alfalfa Meal to High Corn Chick Rations
Feeding trials were conducted on three groups of chicks in eight lots receiving a growing mash containing dehydrated alfalfa meal at levels of 2, 3, 4, 5, 6, 9, 10, 12, and 15 per cent. Comparisons were not made simultaneously but no general trend toward growth depression was evident in comparable lots. In addition duplicate trials of four lots of newly hatched New Hampshire chicks were made on pelleted rations carrying 0, 2, 4, and 6 per cent of a good quality dehydrated alfalfa meal. The chicks were all fed accurately known amounts of the pelleted rations for six weeks. In each of the duplicate trials the lot fed 2 per cent alfalfa meal made slightly better gains than the other lots. The lots fed 4 and 6 per cent alfalfa made as good gains as the control lots fed no alfalfa. It is evident that with the sample of dehydrated alfalfa meal used in these experiments no adverse effect was produced by the alfalfa. Another trial of four lots was made on rations containing 0, 5, 10 and 15 per cent of alfalfa meal. In this case equal gains were made by each of the alfalfa-fed lots and all were better than the control without alfalfa. It is also seen that the efficiency of gain was higher in the alfalfa-fed lots than in the control. Perhaps most interesting of all is the difference in time required to finish equal amounts of feed. Here the advantage is definitely in favor of the alfalfa-fed lots
The Utilization of Food Elements by Growing Chicks. XIII. The Effect of Additions of Dehydrated Alfalfa Meal to High Corn Chick Rations
Feeding trials were conducted on three groups of chicks in eight lots receiving a growing mash containing dehydrated alfalfa meal at levels of 2, 3, 4, 5, 6, 9, 10, 12, and 15 per cent. Comparisons were not made simultaneously but no general trend toward growth depression was evident in comparable lots. In addition duplicate trials of four lots of newly hatched New Hampshire chicks were made on pelleted rations carrying 0, 2, 4, and 6 per cent of a good quality dehydrated alfalfa meal. The chicks were all fed accurately known amounts of the pelleted rations for six weeks. In each of the duplicate trials the lot fed 2 per cent alfalfa meal made slightly better gains than the other lots. The lots fed 4 and 6 per cent alfalfa made as good gains as the control lots fed no alfalfa. It is evident that with the sample of dehydrated alfalfa meal used in these experiments no adverse effect was produced by the alfalfa. Another trial of four lots was made on rations containing 0, 5, 10 and 15 per cent of alfalfa meal. In this case equal gains were made by each of the alfalfa-fed lots and all were better than the control without alfalfa. It is also seen that the efficiency of gain was higher in the alfalfa-fed lots than in the control. Perhaps most interesting of all is the difference in time required to finish equal amounts of feed. Here the advantage is definitely in favor of the alfalfa-fed lots
A New Approach to Spin and Statistics
We give an algebraic proof of the spin-statistics connection for the
parabosonic and parafermionic quantum topological charges of a theory of local
observables with a modular PCT-symmetry. The argument avoids the use of the
spinor calculus and also works in 1+2 dimensions. It is expected to be a
progress towards a general spin-statistics theorem including also
(1+2)-dimensional theories with braid group statistics.Comment: LATEX, 15 pages, no figure
Flight Research at Ames: Fifty-Seven Years of Development and Validation of Aeronautical Technology
This NASA special publication presents a general overview of the flight research that has been conducted at Ames Research Center over the last 57 years. Icing research, transonic model testing, aerodynamics, variable stability aircraft, boundary layer control, short takeoff and landing (STOL), vertical/ short takeoff and landing (V/STOL) and rotorcraft research are among the major topics of interest discussed. Flying qualities, stability and control, performance evaluations, gunsight tracking and guidance and control displays research are also presented. An epilogue is included which presents the significant contributions that came about as a result of research and development conducted at Ames
The second law of thermodynamics, TCP, and Einstein causality in anti-de Sitter space-time
If the vacuum is passive for uniformly accelerated observers in anti-de
Sitter space-time (i.e. cannot be used by them to operate a "perpetuum
mobile"), they will (a) register a universal value of the Hawking-Unruh
temperature, (b) discover a TCP symmetry, and (c) find that observables in
complementary wedge-shaped regions are commensurable (local) in the vacuum
state. These results are model independent and hold in any theory which is
compatible with some weak notion of space-time localization.Comment: 8 pages, slightly improved results, minor changes in the expository
part, new title; to appear in "Classical and Quantum Gravity
- …