1,348 research outputs found

### A pair potential supporting a mixed mean-field / BCS- phase

We construct a Hamiltonian which in a scaling limit becomes equivalent to one
that can be diagonalized by a Bogoliubov transformation. There may appear
simultaneously a mean-field and a superconducting phase. They influence each
other in a complicated way. For instance, an attractive mean field may
stimulate the superconducting phase and a repulsive one may destroy it.Comment: 11 pages, 5 figures, LaTe

### Gravitational Field of a Spinning Cosmic String

We study the effect of internal space rotation on the gravitational
properties of infinite straight and stationary cosmic string. From the
approximate solution of Einsten equations for the spinning Q-lump string we
obtain long range gravitational accelleration resembling that of a rotating
massive cylindrical shell. We also compute the angular velocity of the inertial
frame dragging and the angle of light deflection by the Q-lump string. Matter
accretion on to spinning strings can play a role in galaxy formation when the
angular velocity times the string width is comparable to the speed of light.Comment: 14 page

### MEASURING GRAVITOMAGNETIC EFFECTS BY MEANS OF RING LASERS

Light is a good probe for general relativistic effects. Exploiting the asymmetry of the propagation in the vicinity of a central rotating mass it is possible to use a ring laser in order to measure the frame dragging of the reference frames by the gravitational field of the Earth (Lense-Thirring effect). I shall present the G-GranSasso experiment whose objective is precisely to measure the Lense-Thirring and the de Sitter effects in a terrestrial laboratory. The experimental apparatus will be made of a set of at least three, differently oriented, ring lasers rigidly attached to a central "monument". The signal will be in the form of the beat frequency produced in the annular cavity of each laser by the rotational anisotropy. The laboratory will be located underground in the Laboratori Nazionali del Gran Sasso facility, in Italy. The required sensitivity is just one order of magnitude below the performance of the best existing instruments and the new design will attain i

### High-$T_c$ superconductivity by phase cloning

We consider a BCS-type model in the spin formalism and argue that the
structure of the interaction provides a mechanism for control over directions
of the spin \vect S other than $S_z$, which is being controlled via the
conventional chemical potential. We also find the conditions for the appearance
of a high-$T_c$ superconducting phase.Comment: 11 pages, 5 figures v3: section 2 edite

### Second-quantization picture of the edge currents in the fractional quantum Hall effect

We study the quantum theory of two-dimensional electrons in a magnetic field
and an electric field generated by a homogeneous background. The dynamics
separates into a microscopic and macroscopic mode. The latter is a circular
Hall current which is described by a chiral quantum field theory. It is shown
how in this second quantized picture a Laughlin-type wave function emerges.Comment: 12 pages, 1 figure, LaTeX; comments on the particle density and the
charge added, the figure improve

### Analysis of the exactness of mean-field theory in long-range interacting systems

Relationships between general long-range interacting classical systems on a
lattice and the corresponding mean-field models (infinitely long-range
interacting models) are investigated. We study systems in arbitrary dimension d
for periodic boundary conditions and focus on the free energy for fixed value
of the total magnetization. As a result, it is shown that the equilibrium free
energy of the long-range interacting systems are exactly the same as that of
the corresponding mean-field models (exactness of the mean-field theory).
Moreover, the mean-field metastable states can be also preserved in general
long-range interacting systems. It is found that in the case that the
magnetization is conserved, the mean-field theory does not give correct
property in some parameter region.Comment: 4 pages, 5 figures; clarifications and discussion about boundary
effects is added; the title is change

### Do anyons solve Heisenberg's Urgleichung in one dimension

We construct solutions to the chiral Thirring model in the framework of
algebraic quantum field theory. We find that for all positive temperatures
there are fermionic solutions only if the coupling constant is $\lambda =
\sqrt{2(2n + 1)\pi}, n \in \bf N$.Comment: 19 pages LaTeX, to appear in Eur. Phys. J.

### Noncommutative Manifolds from the Higgs Sector of Coincident D-Branes

The Higgs sector of the low-energy physics of n of coincident D-branes
contains the necessary elements for constructing noncommutative manifolds. The
coordinates orthogonal to the coincident branes, as well as their conjugate
momenta, take values in the Lie algebra of the gauge group living inside the
brane stack. In the limit when n=\infty (and in the absence of orientifolds),
this is the unitary Lie algebra u(\infty). Placing a smooth manifold K
orthogonally to the stack of coincident D-branes one can construct a
noncommutative C*-algebra that provides a natural definition of a
noncommutative partner for the manifold K.Comment: 10 page

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