16 research outputs found
Boundary contributions to specific heat and susceptibility in the spin-1/2 XXZ chain
Exact low-temperature asymptotic behavior of boundary contribution to
specific heat and susceptibility in the one-dimensional spin-1/2 XXZ model with
exchange anisotropy 1/2 < \Delta \le 1 is analytically obtained using the
Abelian bosonization method. The boundary spin susceptibility is divergent in
the low-temperature limit. This singular behavior is caused by the first-order
contribution of a bulk leading irrelevant operator to boundary free energy. The
result is confirmed by numerical simulations of finite-size systems. The
anomalous boundary contributions in the spin isotropic case are universal.Comment: 6 pages, 3 figures; corrected typo
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Surface permeability of porous media particles and capillary transport
We have established previously, in a lead-in study, that the spreading of liquids in particulate
porous media at low saturation levels, characteristically less than 10% of the void space, has very
distinctive features in comparison to that at higher saturation levels. In particular, we have found
that the dispersion process can be accurately described by a special class of partial differential
equations, the super-fast non-linear diffusion equation. The results of mathematical modelling have
demonstrated very good agreement with experimental observations. However, any enhancement of
the accuracy and predictive power of the model, keeping in mind practical applications, requires the
knowledge of the effective surface permeability of the constituent particles, which defines the global,
macroscopic permeability of the particulate media. In the paper, we demonstrate how this quantity
can be determined through the solution of the Laplace-Beltrami Dirichlet problem, we study this
using the well-developed surface finite element method
Z_3 Quantum Criticality in a spin-1/2 chain model
The stability of the magnetization plateau phase of the XXZ spin-1/2
Heisenberg chain with competing interactions is investigated upon switching on
a staggered transverse magnetic field. Within a bosonization approach, it is
shown that the low-energy properties of the model are described by an effective
two-dimensional XY model in a three-fold symmetry-breaking field. A phase
transition in the three-state Potts universality class is expected separating
the plateau phase to a phase where the spins are polarized along the
staggered magnetic field. The Z critical properties of the transition are
determined within the bosonization approach.Comment: 5 pages, revised versio
Elliptic hypergeometry of supersymmetric dualities II. Orthogonal groups, knots, and vortices
We consider Seiberg electric-magnetic dualities for 4d SYM
theories with SO(N) gauge group. For all such known theories we construct
superconformal indices (SCIs) in terms of elliptic hypergeometric integrals.
Equalities of these indices for dual theories lead both to proven earlier
special function identities and new conjectural relations for integrals. In
particular, we describe a number of new elliptic beta integrals associated with
the s-confining theories with the spinor matter fields. Reductions of some
dualities from SP(2N) to SO(2N) or SO(2N+1) gauge groups are described.
Interrelation of SCIs and the Witten anomaly is briefly discussed. Possible
applications of the elliptic hypergeometric integrals to a two-parameter
deformation of 2d conformal field theory and related matrix models are
indicated. Connections of the reduced SCIs with the state integrals of the knot
theory, generalized AGT duality for (3+3)d theories, and a 2d vortex partition
function are described.Comment: Latex, 58 pages; paper shortened, to appear in Commun. Math. Phy
Red fluorescent protein with reversibly photoswitchable absorbance for photochromic FRET
SummaryWe have developed the first red fluorescent protein, named rsTagRFP, which possesses reversibly photoswitchable absorbance spectra. Illumination with blue and yellow light switches rsTagRFP into a red fluorescent state (ON state) or nonfluorescent state (OFF state), respectively. The ON and OFF states exhibit absorbance maxima at 567 and 440 nm, respectively. Due to the photoswitchable absorbance, rsTagRFP can be used as an acceptor for a photochromic Förster resonance energy transfer (pcFRET). The photochromic acceptor facilitates determination of a protein-protein interaction by providing an internal control for FRET. Using pcFRET with EYFP as a donor, we observed an interaction between epidermal growth factor receptor and growth factor receptor-binding protein 2 in live cells by detecting the modulation of both the fluorescence intensity and lifetime of the EYFP donor upon the ON-OFF photoswitching of the rsTagRFP acceptor
Bright monomeric red fluorescent protein with an extended fluorescence lifetime.
Fluorescent proteins have become extremely popular tools for in vivo imaging and especially for the study of localization, motility and interaction of proteins in living cells. Here we report TagRFP, a monomeric red fluorescent protein, which is characterized by high brightness, complete chromophore maturation, prolonged fluorescence lifetime and high pH-stability. These properties make TagRFP an excellent tag for protein localization studies and fluorescence resonance energy transfer (FRET) applications