2,809 research outputs found
Eigenvectors of tensors - A primer
We give an introduction to the theory and to some applications of
eigenvectors of tensors (in other words, invariant one-dimensional subspaces of
homogeneous polynomial maps), including a review of some concepts that are
useful for their discussion. The intent is to give practitioners an overview of
fundamental notions, results and techniques
Building the red sequence through gas-rich major mergers
Understanding the details of how the red sequence is built is a key question
in galaxy evolution. What are the relative roles of gas-rich vs. dry mergers,
major vs. minor mergers or galaxy mergers vs. gas accretion? In Wild et al.
2009 we compare hydrodynamic simulations with observations to show how gas-rich
major mergers result in galaxies with strong post-starburst spectral features,
a population of galaxies easily identified in the real Universe using optical
spectra. Using spectra from the VVDS deep survey with z~0.7, and a principal
component analysis technique to provide indices with high enough SNR, we find
that 40% of the mass flux onto the red-sequence could enter through a strong
post-starburst phase, and thus through gas-rich major mergers. The deeper
samples provided by next generation galaxy redshift surveys will allow us to
observe the primary physical processes responsible for the shut-down in
starformation and build-up of the red sequence.Comment: 4 pages, 7 figures, proceedings of IAU symposium 262 "Stellar
populations, planning for the next decade
Rational Conformal Field Theories With G_2 Holonomy
We study conformal field theories for strings propagating on compact,
seven-dimensional manifolds with G_2 holonomy. In particular, we describe the
construction of rational examples of such models. We argue that analogues of
Gepner models are to be constructed based not on N=1 minimal models, but on Z_2
orbifolds of N=2 models. In Z_2 orbifolds of Gepner models times a circle, it
turns out that unless all levels are even, there are no new Ramond ground
states from twisted sectors. In examples such as the quintic Calabi-Yau, this
reflects the fact that the classical geometric orbifold singularity can not be
resolved without violating G_2 holonomy. We also comment on supersymmetric
boundary states in such theories, which correspond to D-branes wrapping
supersymmetric cycles in the geometry.Comment: 20 pages, harvmac(b); v2: ref. adde
Long Range Structure of the Nucleon
The long range structure of the nucleon is discussed starting from the old
model of a quark bag with a pion cloud (``cloudy bag'') carrying on to the more
recent ideas of the parton model of the nucleon. On the basis of the most
recent measurements of the form factors at MAMI, JLab and MIT quantitative
results for nucleon charge densities are presented within both non-relativistic
and relativistic frameworks.Comment: 14 pages, 14 figure
On the unipotence of autoequivalences of toric complete intersection Calabi-Yau categories
We identify a class of autoequivalences of triangulated categories of
singularities associated with Calabi-Yau complete intersections in toric
varieties. Elements of this class satisfy relations that are directly linked to
the toric data.Comment: 17 page
Matrix Factorizations and Kauffman Homology
The topological string interpretation of homological knot invariants has led
to several insights into the structure of the theory in the case of sl(N). We
study possible extensions of the matrix factorization approach to knot homology
for other Lie groups and representations. In particular, we introduce a new
triply graded theory categorifying the Kauffman polynomial, test it, and
predict the Kauffman homology for several simple knots.Comment: 45 pages, harvma
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