142 research outputs found
Uniform symplicity of groups with proximal action
We prove that groups acting boundedly and order-primitively on linear orders
or acting extremly proximality on a Cantor set (the class including various
Higman-Thomson groups and Neretin groups of almost automorphisms of regular
trees, also called groups of spheromorphisms) are uniformly simple. Explicit
bounds are provided.Comment: 23 pages, appendix by Nir Lazarovich, corrected versio
In-medium antikaon and eta-meson interactions and bound states
The role played by subthreshold meson-baryon dynamics is demonstrated in
kaonic-atom, Kbar-nuclear and eta-nuclear bound-state calculations within
in-medium models of Kbar-N and eta-N interactions. New analyses of kaonic atom
data reveal appreciable multi-nucleon contributions. Calculations of
eta-nuclear bound states show, in particular, that the eta-N scattering length
is not a useful indicator of whether or not eta mesons bind in nuclei nor of
the widths anticipated for such states.Comment: invited talk at the Second International Symposium on Mesic Nuclei,
Cracow, Sept.22-24 2013, matches published versio
B(He) from short range effective field theory
We present an effective field theory (EFT) at leading order to describe light
single- hypernuclei. Owing to the weak binding and to the
short interaction range, meson exchange forces are approximated by
contact interactions within a pionless EFT where the only degrees of freedom
are baryons. At leading order, the -nuclear interaction contains two
2-body (singlet and triplet) and three 3-body interaction terms, a total of 5
terms associated with 5 coupling strengths or low energy constants (LECs). We
adopt the 2-body LECs from hyperon-nucleon scattering data and interaction
models that constrain the scattering lengths, while the 3-body LECs
are adjusted using both 3-body and 4-body hypernuclear binding energies. To
calculate the binding energies for A-body systems with A2, we expand the
wavefunctions using a correlated Gaussian basis. The stochastic variational
method is employed to select the non-linear parameters. The resulting
\nopieft~is then applied to calculate the separation energy in
He, where the adjusted 3-body interactions largely resolve the
known overbinding problem of He.Comment: HYP2018 conference proceedin
Onset of nuclear binding
Recent studies of nuclear quasibound states by the Jerusalem-Prague
Collaboration are reviewed, focusing on stochastic variational method self
consistent calculations of few-nucleon systems. These calculations
suggest that a minimum value Re fm (0.7 fm) is needed
to bind \eta\,^3He (\eta\,^4He).Comment: presented by A. Gal at EXA2017, Vienna, Sept. 2017; written up for
EPJ Web of Conference
It is all about where you start: Text-to-image generation with seed selection
Text-to-image diffusion models can synthesize a large variety of concepts in
new compositions and scenarios. However, they still struggle with generating
uncommon concepts, rare unusual combinations, or structured concepts like hand
palms. Their limitation is partly due to the long-tail nature of their training
data: web-crawled data sets are strongly unbalanced, causing models to
under-represent concepts from the tail of the distribution. Here we
characterize the effect of unbalanced training data on text-to-image models and
offer a remedy. We show that rare concepts can be correctly generated by
carefully selecting suitable generation seeds in the noise space, a technique
that we call SeedSelect. SeedSelect is efficient and does not require
retraining the diffusion model. We evaluate the benefit of SeedSelect on a
series of problems. First, in few-shot semantic data augmentation, where we
generate semantically correct images for few-shot and long-tail benchmarks. We
show classification improvement on all classes, both from the head and tail of
the training data of diffusion models. We further evaluate SeedSelect on
correcting images of hands, a well-known pitfall of current diffusion models,
and show that it improves hand generation substantially
In-medium antikaon interactions and bound states
Correct treatment of subthreshold Kbar-N dynamics is mandatory in kaonic-atom
and Kbar-nuclear bound-state calculations, as demonstrated by using in-medium
chirally-based models of Kbar-N interactions. Recent studies of kaonic-atom
data reveal appreciable multi-nucleon contributions. Kbar-nuclear widths larger
than 50 MeV are anticipated.Comment: Invited talk by A. Gal in MESON 2014, Cracow, May-June 2014, written
up for EPJ Web of Conferences, updating an earlier Conference Proceedings
(arXiv:1402.3778
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