604 research outputs found
Quantum Loop Representation for Fermions coupled to Einstein-Maxwell field
Quantization of the system comprising gravitational, fermionic and
electromagnetic fields is developed in the loop representation. As a result we
obtain a natural unified quantum theory. Gravitational field is treated in the
framework of Ashtekar formalism; fermions are described by two Grassmann-valued
fields. We define a -algebra of configurational variables whose
generators are associated with oriented loops and curves; ``open'' states --
curves -- are necessary to embrace the fermionic degrees of freedom. Quantum
representation space is constructed as a space of cylindrical functionals on
the spectrum of this -algebra. Choosing the basis of ``loop'' states we
describe the representation space as the space of oriented loops and curves;
then configurational and momentum loop variables become in this basis the
operators of creation and annihilation of loops and curves. The important
difference of the representation constructed from the loop representation of
pure gravity is that the momentum loop operators act in our case simply by
joining loops in the only compatible with their orientaiton way, while in the
case of pure gravity this action is more complicated.Comment: 28 pages, REVTeX 3.0, 15 uuencoded ps-figures. The construction of
the representation has been changed so that the representation space became
irreducible. One part is removed because it developed into a separate paper;
some corrections adde
On Holomorphic Factorization in Asymptotically AdS 3D Gravity
This paper studies aspects of ``holography'' for Euclidean signature pure
gravity on asymptotically AdS 3-manifolds. This theory can be described as
SL(2,C) CS theory. However, not all configurations of CS theory correspond to
asymptotically AdS 3-manifolds. We show that configurations that do have the
metric interpretation are parameterized by the so-called projective structures
on the boundary. The corresponding asymptotic phase space is shown to be the
cotangent bundle over the Schottky space of the boundary. This singles out a
``gravitational'' sector of the SL(2,C) CS theory. It is over this sector that
the path integral has to be taken to obtain the gravity partition function. We
sketch an argument for holomorphic factorization of this partition function.Comment: 32+1 pages, no figures; (v2) one reference added, a statement
regarding priorities modified; (v3) presentational changes, an important sign
mistake correcte
Radiation of Quantized Black Hole
The maximum entropy of a quantized surface is demonstrated to be proportional
to the surface area in the classical limit. The general structure of the
horizon spectrum and the value of the Barbero-Immirzi parameter are found. The
discrete spectrum of thermal radiation of a black hole fits naturally the Wien
profile. The natural widths of the lines are very small as compared to the
distances between them. The total intensity of the thermal radiation is
calculated.Comment: 11 pages; few comments and a reference added; one more reference and
a comment on it added; a note added that the natural widths of the lines are
very small as compared to the distances between the
Field induced d_x^2-y^2+id_xy state in d-density-wave metals
We argue that the d_{xy} component of the order parameter can be generated to
form the d_x^2-y^2+id_xy-density wave state by the external magnetic field. The
driving force for this transition is the coupling of the magnetic field with
the orbital magnetism. The fully gapped particle spectrum and the magnetically
active collective mode of the condensate are discussed as a possible signature
of the d+id' density wave state.Comment: 5 pages, 2 color figure
Intrinsic tunneling spectra of Bi_2(Sr_{2-x}La_x)CuO_6
We have measured intrinsic-tunneling spectra of a single CuO-layer La-doped
Bi_2Sr_{2-x}La_xCuO_{6+\delta} (Bi2201-La_x). Despite a difference of a factor
of three in the optimal superconducting critical temperatures for
Bi2201-La_{0.4} and Bi2212 (32 and 95 K, respectively) and different spectral
energy scales, we find that the pseudogap vanishes at a similar characteristic
temperature T*\approx 230-300K for both compounds. We find also that in
Bi2201-La_x, PG humps are seen as sharp peaks and, in fact, even dominate the
intrinsic spectra.Comment: Submitted to Phys. Rev. Let
Lambda<0 Quantum Gravity in 2+1 Dimensions I: Quantum States and Stringy S-Matrix
We consider the theory of pure gravity in 2+1 dimensions, with negative
cosmological constant. The theory contains simple matter in the form of point
particles; the later are classically described as lines of conical
singularities. We propose a formalism in which quantum amplitudes for process
involving black holes and point particles are obtained as Liouville field
theory (LFT) correlation functions on Riemann surfaces X. Point particles are
described by LFT vertex operators, black holes (asymptotic regions) are in
correspondence with boundaries of X. We analyze two examples: the amplitude for
emission of a particle by the BTZ black hole, and the amplitude of black hole
creation by two point particles. We then define an inner product between
quantum states. The value of this inner product can be interpreted as the
amplitude for one set of point particles to go into another set producing black
holes. The full particle S-matrix is then given by the sum of all such
amplitudes. This S-matrix is that of a non-critical string theory, with the
world-sheet CFT being essentially the Liouville theory. Lambda<0 quantum
gravity in 2+1 dimensions is thus a string theory.Comment: v1: 22+1 pages, figures, v2: 25+1 pages, remarks on entropy and
unitarity adde
Coherent states, constraint classes, and area operators in the new spin-foam models
Recently, two new spin-foam models have appeared in the literature, both
motivated by a desire to modify the Barrett-Crane model in such a way that the
imposition of certain second class constraints, called cross-simplicity
constraints, are weakened. We refer to these two models as the FKLS model, and
the flipped model. Both of these models are based on a reformulation of the
cross-simplicity constraints. This paper has two main parts. First, we clarify
the structure of the reformulated cross-simplicity constraints and the nature
of their quantum imposition in the new models. In particular we show that in
the FKLS model, quantum cross-simplicity implies no restriction on states. The
deeper reason for this is that, with the symplectic structure relevant for
FKLS, the reformulated cross-simplicity constraints, in a certain relevant
sense, are now \emph{first class}, and this causes the coherent state method of
imposing the constraints, key in the FKLS model, to fail to give any
restriction on states. Nevertheless, the cross-simplicity can still be seen as
implemented via suppression of intertwiner degrees of freedom in the dynamical
propagation. In the second part of the paper, we investigate area spectra in
the models. The results of these two investigations will highlight how, in the
flipped model, the Hilbert space of states, as well as the spectra of area
operators exactly match those of loop quantum gravity, whereas in the FKLS (and
Barrett-Crane) models, the boundary Hilbert spaces and area spectra are
different.Comment: 21 pages; statements about gamma limits made more precise, and minor
phrasing change
In-plane Tunneling Spectrum into a [110]-Oriented High- Superconductor in the Pseudogap Regime
Both the differential tunneling conductance and the surface local density of
states (LDOS) of a [110]-oriented high-temperature superconductor in the
pseudogap (PG) regime are studied theoretically. As a competing candidate for
the mechanism of PG state, the charge-density wave (CDW), spin-density wave
(SDW), -density wave (DDW), and d-wave superconducting (DSC) orderings show
distinct features in the tunneling conductance. For the CDW, SDW, and DSC
orderings, the tunneling conductance approaches the surface LDOS as the barrier
potential is increased. For the DDW ordering, we show for the first time that
there exist midgap states at the [110] surface, manifesting themselves as a
sharp zero-energy peak in the LDOS, as in the case of DSC ordering. However,
due to the particle-hole pair nature of the DDW state, these states do not
carry current, and consequently the one-to-one correspondence between the
tunneling conductance and the surface LDOS is absent.Comment: 5 pages, 4 figures embedded in the tex
Quantitative trait loci and genes associated with salmonid alphavirus load in Atlantic salmon:implications for pancreas disease resistance and tolerance
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