13,953 research outputs found
Dewetting of a solid monolayer
We report on the dewetting of a monolayer on a solid substrate, where mass
transport occurs via surface diffusion. For a wide range of parameters, a
labyrinthine pattern of bilayer islands is formed. An irreversible regime and a
thermodynamic regime are identified. In both regimes, the velocity of a
dewetting front, the wavelength of the bilayer island pattern, and the rate of
nucleation of dewetted zones are obtained. We also point out the existence of a
scaling behavior, which is analyzed by means of a geometrical model.Comment: to be published in PhysRevLet
Little IIB Matrix Model
We study the zero-dimensional reduced model of D=6 pure super Yang-Mills
theory and argue that the large N limit describes the (2,0) Little String
Theory. The one-loop effective action shows that the force exerted between two
diagonal blocks of matrices behaves as 1/r^4, implying a six-dimensional
spacetime. We also observe that it is due to non-gravitational interactions. We
construct wave functions and vertex operators which realize the D=6, (2,0)
tensor representation. We also comment on other "little" analogues of the IIB
matrix model and Matrix Theory with less supercharges.Comment: 17 pages, references adde
Interaction induced dimerization in zigzag single wall carbon nanotubes
We derive a low-energy effective model of metallic zigzag carbon nanotubes at
half filling. We show that there are three important features characterizing
the low-energy properties of these systems: the long-range Coulomb interaction,
umklapp scattering and an explicit dimerization generated by interactions. The
ratio of the dimerization induced gap and the Mott gap induced by the umklapp
interactions is dependent on the radius of the nanotube and can drive the
system through a quantum phase transition with SU(2)_1 quantum symmetry. We
consider the physical properties of the phases on either side of this
transition which should be relevant for realistic nanotubes.Comment: 8 pages, 5 figure
Describing gluons at zero and finite temperature
Any description of gluons requires a well-defined gauge. This is complicated
non-perturbatively by Gribov copies. A possible method-independent gauge
definition to resolve this problem is presented and afterwards used to study
the properties of gluons at any temperature. It is found that only
chromo-electric properties reflect the phase transition. From these the
gauge-invariant phase transition temperature is determined for SU(2) and SU(3)
Yang-Mills theory independently.Comment: 3 pages, 1 figure. Talk given at "The 5-th International Conference
on Quarks and Nuclear Physics", Beijing, China, and at "Quarks, Hadrons, and
the Phase Diagram of QCD", St. Goar, Germany, both September 2009. Submitted
to the QNP proceeding
Polaron Induced Deformations in Carbon Nanotubes
We compute for the first time full elastic deformations, as well as length,
of self-trapped electronic states in carbon nanotubes of general radius and
chirality, within the unifying framework of a recently introduced two field
model for electromechanics of carbon nano-structures. We find that deformations
are highly non monotonic in the chiral angle, whereas the length of the polaron
is not. Applications include nano-mechanical devices as electrically or
optically driven nano-actuators.Comment: 4 Pages, 1 Figure Phys Rev B Brief Repor
Intersubband Edge Singularity in Metallic Nanotubes
Tunneling density of states of both the massless and massive (gapped)
particles in metallic carbon nanotubes is known to have anomalous energy
dependence. This is the result of coupling to multiple low-energy bosonic
excitation (plasmons). For both kinds of particles the ensuing effect is the
suppression of the density of states by electron-electron interactions. We
demonstrate that the optical absorption between gapless and gapped states is
affected by the many-body effects in the opposite way. The absorption
probability is enhanced compared with the non-interacting value and develops a
power-law frequency dependence with the exponent -0.2 for typical nanotubes.Comment: 4 pages, 1 figure (final version, discussion of Sommerfeld factor and
Ref. 11 added
Asymptotic behavior of age-structured and delayed Lotka-Volterra models
In this work we investigate some asymptotic properties of an age-structured
Lotka-Volterra model, where a specific choice of the functional parameters
allows us to formulate it as a delayed problem, for which we prove the
existence of a unique coexistence equilibrium and characterize the existence of
a periodic solution. We also exhibit a Lyapunov functional that enables us to
reduce the attractive set to either the nontrivial equilibrium or to a periodic
solution. We then prove the asymptotic stability of the nontrivial equilibrium
where, depending on the existence of the periodic trajectory, we make explicit
the basin of attraction of the equilibrium. Finally, we prove that these
results can be extended to the initial PDE problem.Comment: 29 page
Chiral symmetry analysis and rigid rotational invariance for the lattice dynamics of single-wall carbon nanotubes
In this paper, we provide a detailed expression of the vibrational potential
for the lattice dynamics of the single-wall carbon nanotubes (SWCNT) satisfying
the requirements of the exact rigid translational as well as rotational
symmetries, which is a nontrivial generalization of the valence force model for
the planar graphene sheet. With the model, the low frequency behavior of the
dispersion of the acoustic modes as well as the flexure mode can be precisely
calculated. Based upon a comprehensive chiral symmetry analysis, the calculated
mode frequencies (including all the Raman and infrared active modes),
velocities of acoustic modes and the polarization vectors are systematically
fitted in terms of the chiral angle and radius, where the restrictions of
various symmetry operations of the SWCNT are fulfilled
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