214 research outputs found
Noncommutative Solitons
Solitonic objects play a central role in gauge and string theory (as, e.g.,
monopoles, black holes, D-branes, etc.). Certain string backgrounds produce a
noncommutative deformation of the low-energy effective field theory, which
allows for new types of solitonic solutions. I present the construction, moduli
spaces and dynamics of Moyal-deformed solitons, exemplified in the 2+1
dimensional Yang-Mills-Higgs theory and its Bogomolny system, which is
gauge-fixed to an integrable chiral sigma model (the Ward model).
Noncommutative solitons for various 1+1 dimensional integrable systems (such as
sine-Gordon) easily follow by dimensional and algebraic reduction.
Supersymmetric extensions exist as well and are related to twistor string
theory.Comment: 16 pages; talk given at the Third Mexican Meeting on Mathematical and
Experimental Physics at El Colegio Nacional, Mexico City, 10-14 September
200
Ученому секретарю Редколлегии журнала "Известия ТПУ" доценту С. Б. Могильницкому - 60 лет
Описан жизненный путь, личные качества, учебная и научная деятельность и достижения ученого секретаря Редколлегии журнала "Известия ТПУ", кандидата физико-математических наук, доцента Томского политехнического университета Сергея Борисовича Могильницког
The East Gotland Basin (Baltic Sea) as a candidate Global Boundary Stratotype Section and Point for the Anthropocene series
The short sediment core EMB201/7-4 retrieved from the East Gotland Basin, central Baltic Sea, is explored here as a candidate to host the stratigraphical basis for the Anthropocene series and its equivalent Anthropocene epoch, still to be formalized in the Geological Time Scale. The core has been accurately dated back to 1840 CE using a well-established event stratigraphy approach. A pronounced and significant change occurs at 26.5 cm (dated 1956 ± 4 CE) for a range of geochemical markers including 239+240Pu, 241Am, fly-ash particles, DDT (organochlorine insecticide), total organic carbon, and bulk organic carbon stable isotopes. This stratigraphic level, which corresponds to a change in both lithology and sediment colour related to early anthropogenic-triggered eutrophication of the central Baltic Sea, is proposed as a Global Boundary Stratotype Section and Point for the Anthropocene series
CP violation in sbottom decays
We study CP asymmetries in two-body decays of bottom squarks into charginos
and tops. These asymmetries probe the SUSY CP phases of the sbottom and the
chargino sector in the Minimal Supersymmetric Standard Model. We identify the
MSSM parameter space where the CP asymmetries are sizeable, and analyze the
feasibility of their observation at the LHC. As a result, potentially
detectable CP asymmetries in sbottom decays are found, which motivates further
detailed experimental studies for probing the SUSY CP phases.Comment: 29 pages, 7 figure
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Rarity of monodominance in hyperdiverse Amazonian forests.
Tropical forests are known for their high diversity. Yet, forest patches do occur in the tropics where a single tree species is dominant. Such "monodominant" forests are known from all of the main tropical regions. For Amazonia, we sampled the occurrence of monodominance in a massive, basin-wide database of forest-inventory plots from the Amazon Tree Diversity Network (ATDN). Utilizing a simple defining metric of at least half of the trees ≥ 10 cm diameter belonging to one species, we found only a few occurrences of monodominance in Amazonia, and the phenomenon was not significantly linked to previously hypothesized life history traits such wood density, seed mass, ectomycorrhizal associations, or Rhizobium nodulation. In our analysis, coppicing (the formation of sprouts at the base of the tree or on roots) was the only trait significantly linked to monodominance. While at specific locales coppicing or ectomycorrhizal associations may confer a considerable advantage to a tree species and lead to its monodominance, very few species have these traits. Mining of the ATDN dataset suggests that monodominance is quite rare in Amazonia, and may be linked primarily to edaphic factors
The relationship between spasticity in young children (18 months of age) with cerebral palsy and their gross motor function development
<p>Abstract</p> <p>Background</p> <p>It is thought that spasticity has an influence on the development of functional motor abilities among children with cerebral palsy (CP). The extent to which spasticity is associated with the change in motor abilities in young children with CP has not been established. The objective of this study is to evaluate the relationship of initial spasticity in young children with CP and their gross motor function development over one year.</p> <p>Methods</p> <p>Fifty children with CP aged 18 months, GMFCS-levels I-V participated in a longitudinal observational study. Change in gross motor functioning (GMFM-66) was measured over one year. The level of spasticity measured at the first assessment was determined with the Modified Tardieu Scale in three muscle groups of the lower extremity (adductor muscles, the hamstrings and the m. gastrocnemius). The Spasticity Total Score per child was calculated with a maximum score of 12 points.</p> <p>Results</p> <p>Spearman's Rho Correlation (-0.28) revealed a statistically significant relationship (p < 0.05) of small strength between the Spasticity Total Score and the change score of the GMFM-66.</p> <p>Conclusion</p> <p>Our findings indicate that when measured over one year, spasticity is marginally related to gross motor function development in infants with CP. The initial level of spasticity is only one of the many child, environmental and family factors that determines gross motor development of a young child with CP.</p
Mass Bounds on a Very Light Neutralino
Within the Minimal Supersymmetric Standard Model (MSSM) we systematically
investigate the bounds on the mass of the lightest neutralino. We allow for
non-universal gaugino masses and thus even consider massless neutralinos, while
assuming in general that R-parity is conserved. Our main focus are laboratory
constraints. We consider collider data, precision observables, and also rare
meson decays to very light neutralinos. We then discuss the astrophysical and
cosmological implications. We find that a massless neutralino is allowed by all
existing experimental data and astrophysical and cosmological observations.Comment: 36 pages, 13 figures, minor modification in astro-physical bounds.
EPJC versio
SUSY CP phases and asymmetries at colliders
In the Minimal Supersymmetric Standard Model, physical phases of complex
parameters lead to CP violation. We show how triple products of particle
momenta or spins can be used to construct asymmetries, that allow us to probe
these CP phases. To give specific examples, we discuss the production of
neutralinos at the International Linear Collider. For the Large Hadron
Collider, we discuss CP asymmetries in squark decays, and in the tri-lepton
signal. We find that the CP asymmetries can be as large as 60%.Comment: 9 pages, 6 figures, To appear in the proceedings of DISCRETE'08:
Symposium on Prospects in the Physics of Discrete Symmetries, Valencia,
Spain, 11-16 Dec 200
Probing SUSY CP Violation in Two-Body Stop Decays at the LHC
We study CP asymmetries in two-body decays of top squarks into neutralinos
and sleptons at the LHC. These asymmetries are used to probe the CP phases
possibly present in the stop and neutralino sector of the Minimal
Supersymmetric Standard Model. Taking into account bounds from experimental
electric dipole moment searches, we identify areas in the mSUGRA parameter
space where CP asymmetries can be sizeable and discuss the feasibility of their
observation at the LHC. As a result, potentially detectable CP asymmetries in
stop decays at the LHC are found, motivating further detailed experimental
studies for probing SUSY CP phases.Comment: 38 pages, 13 figures, error in Yukawa coupling corrected, revised
benchmark scenario and figures, JHEP versio
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