294 research outputs found
BKM Lie superalgebras from counting twisted CHL dyons
Following Sen[arXiv:0911.1563], we study the counting of (`twisted') BPS
states that contribute to twisted helicity trace indices in four-dimensional
CHL models with N=4 supersymmetry. The generating functions of half-BPS states,
twisted as well as untwisted, are given in terms of multiplicative eta products
with the Mathieu group, M_{24}, playing an important role. These multiplicative
eta products enable us to construct Siegel modular forms that count twisted
quarter-BPS states. The square-roots of these Siegel modular forms turn out be
precisely a special class of Siegel modular forms, the dd-modular forms, that
have been classified by Clery and Gritsenko[arXiv:0812.3962]. We show that each
one of these dd-modular forms arise as the Weyl-Kac-Borcherds denominator
formula of a rank-three Borcherds-Kac-Moody Lie superalgebra. The walls of the
Weyl chamber are in one-to-one correspondence with the walls of marginal
stability in the corresponding CHL model for twisted dyons as well as untwisted
ones. This leads to a periodic table of BKM Lie superalgebras with properties
that are consistent with physical expectations.Comment: LaTeX, 32 pages; (v2) matches published versio
INVESTIGATION OF DISCRETE POPULATION BALANCE MODELS AND ITS PARAMETERS FOR TURBULENT EMULSIFICATION PRO- CESSES
Abstract. Different challenges and limitations occur with the simulation of liquid/liquid dispersion using population balance equations (PBE). A limitation is that the breakage and coalescence kernels tend to be specific to the equipment and scale used to acquire the evaluation data. It is reported in literature that PBE simulations are highly scale dependent. Once information is obtained using PBE, it cannot be used, with confidence, for scale-u
Micro-plasticity and intermittent dislocation activity in a simplified micro structural model
Here we present a model to study the micro-plastic regime of a stress-strain
curve. In this model an explicit dislocation population represents the mobile
dislocation content and an internal shear-stress field represents a mean-field
description of the immobile dislocation content. The mobile dislocations are
constrained to a simple dipolar mat geometry and modelled via a dislocation
dynamics algorithm, whilst the shear-stress field is chosen to be a sinusoidal
function of distance along the mat direction. The latter, defined by a periodic
length and a shear-stress amplitude, represents a pre-existing micro-structure.
These model parameters, along with the mobile dislocation density, are found to
admit a diversity of micro-plastic behaviour involving intermittent plasticity
in the form of a scale-free avalanche phenomenon, with an exponent for the
strain burst magnitude distribution similar to those seen in experiment and
more complex dislocation dynamics simulations.Comment: 30 pages, 12 figures, to appear in "Modelling and Simulation in
Materials Science and Engineering
Monitoring global protein thiol-oxidation and protein S-mycothiolation in Mycobacterium smegmatis under hypochlorite stress.
Hillion M, Bernhardt J, Busche T, et al. Monitoring global protein thiol-oxidation and protein S-mycothiolation in Mycobacterium smegmatis under hypochlorite stress. Sci Rep. 2017;7(1): 1195.Mycothiol (MSH) is the major low molecular weight (LMW) thiol in Actinomycetes. Here, we used shotgun proteomics, OxICAT and RNA-seq transcriptomics to analyse protein S-mycothiolation, reversible thiol-oxidations and their impact on gene expression in Mycobacterium smegmatis under hypochlorite stress. In total, 58 S-mycothiolated proteins were identified under NaOCl stress that are involved in energy metabolism, fatty acid and mycolic acid biosynthesis, protein translation, redox regulation and detoxification. Protein S-mycothiolation was accompanied by MSH depletion in the thiol-metabolome. Quantification of the redox state of 1098 Cys residues using OxICAT revealed that 381 Cys residues (33.6%) showed >10% increased oxidations under NaOCl stress, which overlapped with 40 S-mycothiolated Cys-peptides. The absence of MSH resulted in a higher basal oxidation level of 338 Cys residues (41.1%). The RseA and RshA anti-sigma factors and the Zur and NrdR repressors were identified as NaOCl-sensitive proteins and their oxidation resulted in an up-regulation of the SigH, SigE, Zur and NrdR regulons in the RNA-seq transcriptome. In conclusion, we show here that NaOCl stress causes widespread thiol-oxidation including protein S-mycothiolation resulting in induction of antioxidant defense mechanisms in M. smegmatis. Our results further reveal that MSH is important to maintain the reduced state of protein thiols
Generalized Kac-Moody Algebras from CHL dyons
We provide evidence for the existence of a family of generalized
Kac-Moody(GKM) superalgebras, G_N, whose Weyl-Kac-Borcherds denominator formula
gives rise to a genus-two modular form at level N, Delta_{k/2}(Z), for
(N,k)=(1,10), (2,6), (3,4), and possibly (5,2). The square of the automorphic
form is the modular transform of the generating function of the degeneracy of
CHL dyons in asymmetric Z_N-orbifolds of the heterotic string compactified on
T^6. The new generalized Kac-Moody superalgebras all arise as different
`automorphic corrections' of the same Lie algebra and are closely related to a
generalized Kac-Moody superalgebra constructed by Gritsenko and Nikulin. The
automorphic forms, Delta_{k/2}(Z), arise as additive lifts of Jacobi forms of
(integral) weight k/2 and index 1/2. We note that the orbifolding acts on the
imaginary simple roots of the unorbifolded GKM superalgebra, G_1 leaving the
real simple roots untouched. We anticipate that these superalgebras will play a
role in understanding the `algebra of BPS states' in CHL compactifications.Comment: LaTeX, 35 pages; v2: improved referencing and discussion; typos
corrected; v3 [substantial revision] 44 pages, modularity of additive lift
proved, product representation of the forms also given; further references
adde
- …