4,420 research outputs found
About the magnetic fluctuation effect on the phase transition to superconducting state in Al
The free energy and the order parameter profile near the phase transition to
the superconducting state in bulk Al samples are calculated within a
mean-field-like approximation. The results are compared with those for thin
films.Comment: 11 pages, miktex, 2 figure
Solid-state diffusion in amorphous zirconolite
his research utilised Queen Mary's MidPlus computational facilities, supported by QMUL Research-IT and funded by EPSRC grant EP/K000128/1. We are grateful to E. Maddrell for discussions and to CSC for support
Masslessness in -dimensions
We determine the representations of the ``conformal'' group , the restriction of which on the ``Poincar\'e'' subgroup are unitary irreducible. We study their restrictions to the ``De
Sitter'' subgroups and (they remain
irreducible or decompose into a sum of two) and the contraction of the latter
to ``Poincar\'e''. Then we discuss the notion of masslessness in dimensions
and compare the situation for general with the well-known case of
4-dimensional space-time, showing the specificity of the latter.Comment: 34 pages, LaTeX2e, 1 figure. To be published in Reviews in Math. Phy
Free Field Dynamics in the Generalized AdS (Super)Space
Pure gauge representation for general vacuum background fields (Cartan forms)
in the generalized superspace identified with is found. This
allows us to formulate dynamics of free massless fields in the generalized
space-time and to find their (generalized) conformal and higher spin
field transformation laws. Generic solution of the field equations is also
constructed explicitly. The results are obtained with the aid of the star
product realization of ortosymplectic superalgebras.Comment: Some notes added, corrected typo
A Gradient Flow for Worldsheet Nonlinear Sigma Models
We discuss certain recent mathematical advances, mainly due to Perelman, in
the theory of Ricci flows and their relevance for renormalization group (RG)
flows. We consider nonlinear sigma models with closed target manifolds
supporting a Riemannian metric, dilaton, and 2-form B-field. By generalizing
recent mathematical results to incorporate the B-field and by decoupling the
dilaton, we are able to describe the 1-loop beta-functions of the metric and
B-field as the components of the gradient of a potential functional on the
space of coupling constants. We emphasize a special choice of diffeomorphism
gauge generated by the lowest eigenfunction of a certain Schrodinger operator
whose potential and kinetic terms evolve along the flow. With this choice, the
potential functional is the corresponding lowest eigenvalue, and gives the
order alpha' correction to the Weyl anomaly at fixed points of (g(t),B(t)).
Since the lowest eigenvalue is monotonic along the flow and reproduces the Weyl
anomaly at fixed points, it accords with the c-theorem for flows that remain
always in the first-order regime. We compute the Hessian of the lowest
eigenvalue functional and use it to discuss the linear stability of points
where the 1-loop beta-functions vanish, such as flat tori and K3 manifolds.Comment: Accepted version for publication. Citations added to Friedan and to
Fateev, Onofri, and Zamolodchikov. Introduction modified slightly to discuss
these citations. 25 pages, LaTe
Scalar-tensor black holes coupled to Born-Infeld nonlinear electrodynamics
The non-existence of asymptotically flat, neutral black holes and
asymptotically flat, charged black holes in the Maxwell electrodynamics, with
non-trivial scalar field has been proved for a large class of scalar-tensor
theories. The no-scalar-hair theorems, however, do not apply in the case of
non-linear electrodynamics. In the present work numerical solutions describing
charged black holes coupled to Born-Infeld type non-linear electrodynamics in
scalar-tensor theories of gravity with massless scalar field are found. The
causal structure and properties of the solutions are studied, and a comparison
between these solutions and the corresponding solutions in the General
Relativity is made. The presence of the scalar field leads to a much more
simple causal structure. The present class of black holes has a single,
non-degenerate horizon, i.e., its causal structure resembles that of the
Schwarzschild black hole.Comment: 12 pages, 4 figures, PR
Narrow structure in the coherent population trapping resonances in rubidium and Rayleigh scattering
The measurement of the coherent-population-trapping (CPT) resonances in
uncoated Rb vacuum cells has shown that the shape of the resonances is
different in different cells. In some cells the resonance has a complex shape -
a narrow Lorentzian structure, which is not power broadened, superimposed on
the power broadened CPT resonance. The results of the performed investigations
on the fluorescence angular distribution are in agreement with the assumption
that the narrow structure is a result of atom interaction with Rayleigh
scattering light. The results are interesting for indication of the vacuum
cleanness of the cells and building of magnetooptical sensors
In Vivo Imaging of Transplanted Islets with ^(64)Cu-DO3A-VS-Cys^(40)-Exendin-4 by Targeting GLP-1 Receptor
Glucagon-like peptide 1 receptor (GLP-1R) is highly expressed in pancreatic islets, especially on β-cells. Therefore, a properly labeled ligand that binds to GLP-1R could be used for in vivo pancreatic islet imaging. Because native GLP-1 is degraded rapidly by dipeptidyl peptidase-IV (DPP-IV), a more stable agonist of GLP-1 such as Exendin-4 is a preferred imaging agent. In this study, DO3A-VS-Cys^(40)-Exendin-4 was prepared through the conjugation of DO3A-VS with Cys^(40)-Exendin-4. The in vitro binding affinity of DO3A-VS-Cys^(40)-Exendin-4 was evaluated in INS-1 cells, which overexpress GLP-1R. After ^(64)Cu labeling, biodistribution studies and microPET imaging of ^(64)Cu-DO3A-VS-Cys^(40)-Exendin-4 were performed on both subcutaneous INS-1 tumors and islet transplantation models. The subcutaneous INS-1 tumor was clearly visualized with microPET imaging after the injection of ^(64)Cu-DO3A-VS-Cys^(40)-Exendin-4. GLP-1R positive organs, such as pancreas and lung, showed high uptake. Tumor uptake was saturable, reduced dramatically by a 20-fold excess of unlabeled Exendin-4. In the intraportal islet transplantation models, ^(64)Cu-DO3A-VS-Cys^(40)-Exendin-4 demonstrated almost two times higher uptake compared with normal mice. ^(64)Cu-DO3A-VS-Cys^(40)-Exendin-4 demonstrated persistent and specific uptake in the mouse pancreas, the subcutaneous insulinoma mouse model, and the intraportal human islet transplantation mouse model. This novel PET probe may be suitable for in vivo pancreatic islets imaging in the human
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