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Supermembranes and Supermatrix Models  [PDF]
B. de Wit,K. Peeters,J. C. Plefka
Physics , 1997,
Abstract: We briefly review recent developments in the theory of supermembranes and supermatrix models. In a second part we discuss their interaction with background fields. In particular, we present the full background field coupling for the bosonic case. This is a short summary of the talk at the workshop. A more extended version will appear elsewhere.
On Alternative Supermatrix Reduction  [PDF]
Steven Duplij
Mathematics , 1995, DOI: 10.1007/BF00312670
Abstract: We consider a nonstandard odd reduction of supermatrices (as compared with the standard even one) which arises in connection with possible extension of manifold structure group reductions. The study was initiated by consideration of the generalized noninvertible superconformal-like transformations. The features of even- and odd-reduced supermatrices are investigated on a par. They can be unified into some kind of "sandwich" semigroups. Also we define a special module over even- and odd-reduced supermatrix sets, and the generalized Cayley-Hamilton theorem is proved for them. It is shown that the odd-reduced supermatrices represent semigroup bands and Rees matrix semigroups over a unit group.
Paleontological museums and geoethics
Riccardo Manni
Annals of Geophysics , 2012, DOI: 10.4401/ag-5562
Abstract: Paleontological museums should adopt a code of ethics in order to carry out restorations and to set-up exhibits without any falsification. Indeed, alterations can often be voluntary because an exhibit needs to be ‘beautiful’, ‘realistic’ or ‘charming’ for the public. Therefore, the reconstructed parts are painted and then ‘soiled’ artfully to look more realistic. An incomplete skeleton might be completed by reconstructing the missing bones, or by adding casts of other bones. Sometimes skeletons are ‘created’, by assembling together bones from several specimens of the same species. Therefore, the museum staff should also inform visitors if a specimen has undergone such tampering, because otherwise each visitor is convinced that they have seen a ‘true’ fossil. So all museum staff should be trained not only in the techniques of museums, but also in the ethics of restoration and installation.
Duality and integrability of supermatrix model with external source  [PDF]
Taro Kimura
Physics , 2014, DOI: 10.1093/ptep/ptu163
Abstract: We study the Hermitian supermatrix model involving an external source. We derive the determinantal formula for the supermatrix partition function, and also for the expectation value of the characteristic polynomial ratio, which yields the duality between the characteristic polynomial and the external source with an arbitrary matrix potential function. We also show that the supermatrix integral satisfies the one and two dimensional Toda lattice equations as well as the ordinary matrix model.
Molecular and Paleontological Evidence for a Post-Cretaceous Origin of Rodents  [PDF]
Shaoyuan Wu, Wenyu Wu, Fuchun Zhang, Jie Ye, Xijun Ni, Jimin Sun, Scott V. Edwards, Jin Meng, Chris L. Organ
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0046445
Abstract: The timing of the origin and diversification of rodents remains controversial, due to conflicting results from molecular clocks and paleontological data. The fossil record tends to support an early Cenozoic origin of crown-group rodents. In contrast, most molecular studies place the origin and initial diversification of crown-Rodentia deep in the Cretaceous, although some molecular analyses have recovered estimated divergence times that are more compatible with the fossil record. Here we attempt to resolve this conflict by carrying out a molecular clock investigation based on a nine-gene sequence dataset and a novel set of seven fossil constraints, including two new rodent records (the earliest known representatives of Cardiocraniinae and Dipodinae). Our results indicate that rodents originated around 61.7–62.4 Ma, shortly after the Cretaceous/Paleogene (K/Pg) boundary, and diversified at the intraordinal level around 57.7–58.9 Ma. These estimates are broadly consistent with the paleontological record, but challenge previous molecular studies that place the origin and early diversification of rodents in the Cretaceous. This study demonstrates that, with reliable fossil constraints, the incompatibility between paleontological and molecular estimates of rodent divergence times can be eliminated using currently available tools and genetic markers. Similar conflicts between molecular and paleontological evidence bedevil attempts to establish the origination times of other placental groups. The example of the present study suggests that more reliable fossil calibration points may represent the key to resolving these controversies.
Supermatrix models, loop equations, and duality  [PDF]
Patrick Desrosiers,Bertrand Eynard
Physics , 2009, DOI: 10.1063/1.3430564
Abstract: We study integrals over Hermitian supermatrices of arbitrary size $p+q$, that are parametrized by an external field $X$ and a source $Y$, of respective size $m+n$ and $p+q$. We show that these integrals exhibit a simple topological expansion in powers of a formal parameter $\hbar$, which can be identified with $1/(p-q)$. The loop equation and the associated spectral curve are also obtained. The solutions to the loop equation are given in terms of the symplectic invariants introduced in arXiv:math-ph/0702045. The symmetry property of the latter objects allows us to prove a duality that relates supermatrix models in which the role of $X$ and $Y$ are interchanged.
Relationships of Cetacea (Artiodactyla) Among Mammals: Increased Taxon Sampling Alters Interpretations of Key Fossils and Character Evolution  [PDF]
Michelle Spaulding, Maureen A. O'Leary, John Gatesy
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0007062
Abstract: Background Integration of diverse data (molecules, fossils) provides the most robust test of the phylogeny of cetaceans. Positioning key fossils is critical for reconstructing the character change from life on land to life in the water. Methodology/Principal Findings We reexamine relationships of critical extinct taxa that impact our understanding of the origin of Cetacea. We do this in the context of the largest total evidence analysis of morphological and molecular information for Artiodactyla (661 phenotypic characters and 46,587 molecular characters, coded for 33 extant and 48 extinct taxa). We score morphological data for Carnivoramorpha, ?Creodonta, Lipotyphla, and the ?raoellid artiodactylan ?Indohyus and concentrate on determining which fossils are positioned along stem lineages to major artiodactylan crown clades. Shortest trees place Cetacea within Artiodactyla and close to ?Indohyus, with ?Mesonychia outside of Artiodactyla. The relationships of ?Mesonychia and ?Indohyus are highly unstable, however - in trees only two steps longer than minimum length, ?Mesonychia falls inside Artiodactyla and displaces ?Indohyus from a position close to Cetacea. Trees based only on data that fossilize continue to show the classic arrangement of relationships within Artiodactyla with Cetacea grouping outside the clade, a signal incongruent with the molecular data that dominate the total evidence result. Conclusions/Significance Integration of new fossil material of ?Indohyus impacts placement of another extinct clade ?Mesonychia, pushing it much farther down the tree. The phylogenetic position of ?Indohyus suggests that the cetacean stem lineage included herbivorous and carnivorous aquatic species. We also conclude that extinct members of Cetancodonta (whales + hippopotamids) shared a derived ability to hear underwater sounds, even though several cetancodontans lack a pachyostotic auditory bulla. We revise the taxonomy of living and extinct artiodactylans and propose explicit node and stem-based definitions for the ingroup.
Mega-phylogeny approach for comparative biology: an alternative to supertree and supermatrix approaches
Stephen A Smith, Jeremy M Beaulieu, Michael J Donoghue
BMC Evolutionary Biology , 2009, DOI: 10.1186/1471-2148-9-37
Abstract: Here we describe and demonstrate a modified supermatrix method termed mega-phylogeny that uses databased sequences as well as taxonomic hierarchies to make extremely large trees with denser matrices than supermatrices. The two major challenges facing large-scale supermatrix phylogenetics are assembling large data matrices from databases and reconstructing trees from those datasets. The mega-phylogeny approach addresses the former as the latter is accomplished by employing recently developed methods that have greatly reduced the run time of large phylogeny construction. We present an algorithm that requires relatively little human intervention. The implemented algorithm is demonstrated with a dataset and phylogeny for Asterales (within Campanulidae) containing 4954 species and 12,033 sites and an rbcL matrix for green plants (Viridiplantae) with 13,533 species and 1,401 sites.By examining much larger phylogenies, patterns emerge that were otherwise unseen. The phylogeny of Viridiplantae successfully reconstructs major relationships of vascular plants that previously required many more genes. These demonstrations underscore the importance of using large phylogenies to uncover important evolutionary patterns and we present a fast and simple method for constructing these phylogenies.All species on Earth – current estimates exceed 1.8 million – are related through common ancestors in the evolutionary Tree of Life. The construction of this phylogeny is a major endeavor for biology and largely now depends on the unprecedented growth of molecular sequence data available in public databases. Efforts focused on single clades, whole genome sequencing, genomic library construction (ESTs, BACs), and large collaborative efforts, such as NSF's Assembling the Tree of Life project, are contributing to the fast-paced growth of public databases, with more than 92 million sequences stored in the current release of GenBank (release 167). Current efforts to infer really large phylogeneti
Curved Superspaces and Local Supersymmetry in Supermatrix Model  [PDF]
Masanori Hanada,Hikaru Kawai,Yusuke Kimura
Physics , 2006, DOI: 10.1143/PTP.115.1003
Abstract: In a previous paper, we introduced a new interpretation of matrix models, in which any d-dimensional curved space can be realized in terms of d matrices, and the diffeomorphism and the local Lorentz symmetries are included in the ordinary unitary symmetry of the matrix model. Furthermore, we showed that the Einstein equation is naturally obtained, if we employ the standard form of the action, S=-tr([A_a,A_b][A^a,A^b])+.... In this paper, we extend this formalism to include supergravity. We show that the supercovariant derivatives on any d-dimensional curved space can be expressed in terms of d supermatrices, and the local supersymmetry can be regarded as a part of the superunitary symmetry. We further show that the Einstein and Rarita-Schwinger equations are compatible with the supermatrix generalization of the standard action.
Corner view on the crown domain  [PDF]
Bernhard Kroetz
Mathematics , 2007,
Abstract: In this paper I raise a question on the structure of the boundary of the crown domain.
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