462 research outputs found
Automorphisms of the affine SU(3) fusion rules
We classify the automorphisms of the (chiral) level-k affine SU(3) fusion
rules, for any value of k, by looking for all permutations that commute with
the modular matrices S and T. This can be done by using the arithmetic of the
cyclotomic extensions where the problem is naturally posed. When k is divisible
by 3, the automorphism group (Z_2) is generated by the charge conjugation C. If
k is not divisible by 3, the automorphism group (Z_2 x Z_2) is generated by C
and the Altsch\"uler--Lacki--Zaugg automorphism. Although the combinatorial
analysis can become more involved, the techniques used here for SU(3) can be
applied to other algebras.Comment: 21 pages, plain TeX, DIAS-STP-92-4
Symmetries of the Kac-Peterson Modular Matrices of Affine Algebras
The characters of nontwisted affine algebras at fixed level define
in a natural way a representation of the modular group . The
matrices in the image are called the Kac-Peterson modular
matrices, and describe the modular behaviour of the characters. In this paper
we consider all levels of , and for
each of these find all permutations of the highest weights which commute with
the corresponding Kac-Peterson matrices. This problem is equivalent to the
classification of automorphism invariants of conformal field theories, and its
solution, especially considering its simplicity, is a major step toward the
classification of all Wess-Zumino-Witten conformal field theories.Comment: 16 pp, plain te
Tolerance and safety evaluation of N, N-dimethylglycine, a naturally occurring organic compound, as a feed additive in broiler diets
N,N-dimethylglycine (DMG) is a tertiary amino acid that naturally occurs as an intermediate metabolite in choline-to-glycine metabolism. The objective of the present trial was to evaluate tolerance, safety and bioaccumulation of dietary DMG in broilers when supplemented at 1 g and 10 g Na-DMG/kg. A feeding trial was conducted using 480 1-d-old broiler chicks that were randomly allocated to twenty-four pens and fed one of three test diets added with 0, 1 or 10 g Na-DMG/kg during a 39 d growth period. Production performance was recorded to assess tolerance and efficacy of the supplement. At the end of the trial, toxicity was evaluated by means of haematology, plasma biochemistry and histopathology of liver, kidney and heart (n 12), whereas bioaccumulation was assessed on breast meat, liver, blood, kidney and adipose tissue (n 8). Carcass traits were similar between the control and 1 g Na-DMG/kg feed groups (P.0·05), but the feed:gain ratio was significantly improved at 1 g Na-DMG/kg feed compared with the control or the 10-fold dose (P¼0·008). Histological examinations showed no pathological effects and results of haematology and plasma biochemistry revealed similar values between the test groups (P.0·05). Bioaccumulation occurred at the 10-fold dose, but the resulting DMG content in breast meat was comparable with, for instance, wheat bran and much lower than uncooked spinach. In conclusion, DMG at 1 g Na-DMG/kg improved the feed:gain ratio in broilers without DMG being accumulated in consumer parts. Furthermore, dietary supplementation with DMG up to 10 g Na-DMG/kg did not induce toxicity or impaired performance in broilers
One Spin Trace Formalism for
It has been known for some time that there are two methods to calculate with staggered fermions: one is the two spin trace formalism and the other is
the one spin trace formalism. Until now, the two spin trace formalism has been
exclusively used for weak matrix element calculations with staggered fermions.
Here, the one spin trace formalism to calculate with staggered fermions
is explained. It is shown that the one spin trace operators require additional
chiral partner operators in order to keep the continuum chiral behavior. The
renormalization of the one spin trace operators is described and compared with
the two spin trace formalism.Comment: 47 pages, latex, 4 figures are available on reques
Partial Flavor Symmetry Restoration for Chiral Staggered Fermions
We study the leading discretization errors for staggered fermions by first
constructing the continuum effective Lagrangian including terms of O(a^2), and
then constructing the corresponding effective chiral Lagrangian. The terms of
O(a^2) in the continuum effective Lagrangian completely break the SU(4) flavor
symmetry down to the discrete subgroup respected by the lattice theory. We
find, however, that the O(a^2) terms in the potential of the chiral Lagrangian
maintain an SO(4) subgroup of SU(4). It follows that the leading discretization
errors in the pion masses are SO(4) symmetric, implying three degeneracies
within the seven lattice irreducible representations. These predictions hold
also for perturbatively improved versions of the action. These degeneracies are
observed, to a surprising degree of accuracy, in existing data. We argue that
the SO(4) symmetry does not extend to the masses and interactions of other
hadrons (vector mesons, baryons, etc), nor to higher order in a^2. We show how
it is possible that, for physical quark masses of O(a^2), the new SO(4)
symmetry can be spontaneously broken, leading to a staggered analogue of the
Aoki-phase of Wilson fermions. This does not, however, appear to happen for
presently studied versions of the staggered action.Comment: 26 pages, 2 figures (using psfig). Version to appear in PRD
(clarifications added to introduction and section 6; typos corrected;
references updated
Automorphism Modular Invariants of Current Algebras
We consider those two-dimensional rational conformal field theories (RCFTs)
whose chiral algebras, when maximally extended, are isomorphic to the current
algebra formed from some affine non-twisted Kac--Moody algebra at fixed level.
In this case the partition function is specified by an automorphism of the
fusion ring and corresponding symmetry of the Kac--Peterson modular matrices.
We classify all such partition functions when the underlying finite-dimensional
Lie algebra is simple. This gives all possible spectra for this class of RCFTs.
While accomplishing this, we also find the primary fields with second smallest
quantum dimension.Comment: 32 pages, plain Te
In vitro assessment of gastrointestinal tract (GIT) fermentation in pigs: Fermentable substrates and microbial activity
Recently, it has become apparent that GIT fermentation is not only of interest for ruminant animals, but also for monogastrics. While it is now widely accepted that the fermentation process and its resultant end-products can have important influences on animal health, little is known about the microbiological and immunological processes involved. In terms of animal health, most interest at the moment is focussed on those moments in animals’ lives when they are faced with sudden changes resulting in stress. The period of weaning in piglets is a typical example of this. The most easily accomplished and appropriate way to influence GIT fermentation processes is that of dietary intervention. This is reflected by the widespread interest in so-called pre- and pro-biotics. Given the complexities of the interactions occurring in the animal itself, it is hardly surprising that in vitro techniques are being widely used: firstly to examine potential substrates for their fermentability and possible inclusion in diets, and secondly, to assess changes in the microbial populations in response to these substrates. This paper will review the techniques currently in use for these two aspects of monogastric fermentation, and provide examples of their use
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