226 research outputs found
Lithology and palynology of cave floor sediment cores from Wakulla Spring, Wakulla County, Florida
Five short bottom sediment cores taken in Wakulla Spring Wakulla County, Florida, were described lithologically
and sampled for palynological study. Four of the cores were recoveredfrom sediments at the spring cave entrance
(130 feet water depth). One core was taken in a fossil vertebrate bone bed, 280 feet distance into the main spring
cave at a water depth of 240 feet. Sediments in the cores are composed of alternating intervals of quartz sand and
calcilitite, containing freshwater diatoms, freshwater mollusk shells and plant remains. The predominant pollen
present in all cores consists of a periporate variety typical of the herb families Chenopodiaceae and Amaranthaceae.
Arboreal flora, typical of the area surrounding the spring today, represent a very low percentage of thle pollen
assemblage in the cores. Clustered Chenopod-Amaranth type pollen observed in one core suggest minimal transport
prior to deposition, and indicate that the bottom sediments in the cave may be essentially In situ. An absence of
exotic flora suggests a Quaternary age for the sediments. (PDF contains 11 pages.
Possible Lattice Distortions in the Hubbard Model for Graphene
The Hubbard model on the honeycomb lattice is a well known model for
graphene. Equally well known is the Peierls type of instability of the lattice
bond lengths. In the context of these two approximations we ask and answer the
question of the possible lattice distortions for graphene in zero magnetic
field. The answer is that in the thermodynamic limit only periodic,
reflection-symmetric distortions are allowed and these have at most six atoms
per unit cell as compared to two atoms for the undistorted lattice.Comment: 5 pages, 3 figure
Selected Cenozoic Benthic Foraminifera from Florida : poster
(1 poster - no publication date on poster, but since early in series likely to be early 1990's)
Energy Cost to Make a Hole in the Fermi Sea
The change in energy of an ideal Fermi gas when a local one-body potential is
inserted into the system, or when the density is changed locally, are important
quantities in condensed matter physics. We show that they can be rigorously
bounded from below by a universal constant times the value given by the
semiclassical approximation.Comment: 4 pages, final version published in Phys. Rev. Let
Uniqueness and Nondegeneracy of Ground States for in
We prove uniqueness of ground state solutions for the
nonlinear equation in , where
and for and for . Here denotes the fractional Laplacian
in one dimension. In particular, we generalize (by completely different
techniques) the specific uniqueness result obtained by Amick and Toland for
and in [Acta Math., \textbf{167} (1991), 107--126]. As a
technical key result in this paper, we show that the associated linearized
operator is nondegenerate;
i.\,e., its kernel satisfies .
This result about proves a spectral assumption, which plays a central
role for the stability of solitary waves and blowup analysis for nonlinear
dispersive PDEs with fractional Laplacians, such as the generalized
Benjamin-Ono (BO) and Benjamin-Bona-Mahony (BBM) water wave equations.Comment: 45 page
Eigenvalue bounds for Schr\"odinger operators with a homogeneous magnetic field
We prove Lieb-Thirring inequalities for Schr\"odinger operators with a
homogeneous magnetic field in two and three space dimensions. The inequalities
bound sums of eigenvalues by a semi-classical approximation which depends on
the strength of the magnetic field, and hence quantifies the diamagnetic
behavior of the system. For a harmonic oscillator in a homogenous magnetic
field, we obtain the sharp constants in the inequalities.Comment: 12 page
Weakly coupled bound states of Pauli operators
We consider the two-dimensional Pauli operator perturbed by a weakly coupled,
attractive potential. We show that besides the eigenvalues arising from the
Aharonov-Casher zero modes there are two or one (depending on whether the flux
of the magnetic field is integer or not) additional eigenvalues for arbitrarily
small coupling and we calculate their asymptotics in the weak coupling limit.Comment: 19 page
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