2,581 research outputs found
Light-Cone Quantization of the Liouville Model
We present the quantization of the Liouville model defined in light-cone
coordinates in (1,1) signature space. We take advantage of the representation
of the Liouville field by the free field of the Backl\"{u}nd transformation and
adapt the approch by Braaten, Curtright and Thorn.
Quantum operators of the Liouville field ,
, , are constructed consistently in
terms of the free field. The Liouville model field theory space is found to be
restricted to the sector with field momentum , , which
is a closed subspace for the Liouville theory operator algebra.Comment: 16 p, EFI-92-6
Soliton quantization and internal symmetry
We apply the method of collective coordinate quantization to a model of
solitons in two spacetime dimensions with a global symmetry. In
particular we consider the dynamics of the charged states associated with
rotational excitations of the soliton in the internal space and their
interactions with the quanta of the background field (mesons). By solving a
system of coupled saddle-point equations we effectively sum all tree-graphs
contributing to the one-point Green's function of the meson field in the
background of a rotating soliton. We find that the resulting one-point function
evaluated between soliton states of definite charge exhibits a pole on
the meson mass shell and we extract the corresponding S-matrix element for the
decay of an excited state via the emission of a single meson using the standard
LSZ reduction formula. This S-matrix element has a natural interpretation in
terms of an effective Lagrangian for the charged soliton states with an
explicit Yukawa coupling to the meson field. We calculate the leading-order
semi-classical decay width of the excited soliton states discuss the
consequences of these results for the hadronic decay of the resonance
in the Skyrme model.Comment: 23 pages, LA-UR-93-299
Scattering Mechanism in Modulation-Doped Shallow Two-Dimensional Electron Gases
We report on a systematic investigation of the dominant scattering mechanism
in shallow two-dimensional electron gases (2DEGs) formed in modulation-doped
GaAs/Al_{x}Ga_{1-x}As heterostructures. The power-law exponent of the electron
mobility versus density, mu \propto n^{alpha}, is extracted as a function of
the 2DEG's depth. When shallower than 130 nm from the surface, the power-law
exponent of the 2DEG, as well as the mobility, drops from alpha \simeq 1.65
(130 nm deep) to alpha \simeq 1.3 (60 nm deep). Our results for shallow 2DEGs
are consistent with theoretical expectations for scattering by remote dopants,
in contrast to the mobility-limiting background charged impurities of deeper
heterostructures.Comment: 4 pages, 3 figures, modified version as accepted in AP
Power increases situated creativity
The present paper examined whether power was linked with situated creativity. We proposed that powerful (vs powerless) people engage in creative thought when creativity contributes to contextual goals but avoid creative thought when creativity impedes contextual goals. Extending the Situated Focus Theory of Power (Guinote, 2007a; 2010) to creativity, we suggested that powerful people are better able to achieve situational goals because they can flexibly focus on cues that indicate what is required for success in a given context. Across three experiments, we found that powerful (vs powerless) people engaged in more creative thinking when creativity facilitated contextual goals. This was not the case when creativity hindered contextual goals. Further, neither affect (Experiment 2) nor effort (Experiments 1 and 3) contributed to these effects. However, local processing undermined creativity for powerful people, indicating that processing style may contribute to the link between power and situated creativity. These findings suggest that powerful people flexibly vary creativity in line with the situation
A Note on Background (In)dependence
In general quantum systems there are two kinds of spacetime modes, those that
fluctuate and those that do not. Fluctuating modes have normalizable
wavefunctions. In the context of 2D gravity and ``non-critical'' string theory
these are called macroscopic states. The theory is independent of the initial
Euclidean background values of these modes. Non-fluctuating modes have
non-normalizable wavefunctions and correspond to microscopic states. The theory
depends on the background value of these non-fluctuating modes, at least to all
orders in perturbation theory. They are superselection parameters and should
not be minimized over. Such superselection parameters are well known in field
theory. Examples in string theory include the couplings (including the
cosmological constant) in the matrix models and the mass of the two-dimensional
Euclidean black hole. We use our analysis to argue for the finiteness of the
string perturbation expansion around these backgrounds.Comment: 16 page
Quantum Hamilton-Jacobi equation
The nontrivial transformation of the phase space path integral measure under
certain discretized analogues of canonical transformations is computed. This
Jacobian is used to derive a quantum analogue of the Hamilton-Jacobi equation
for the generating function of a canonical transformation that maps any quantum
system to a system with a vanishing Hamiltonian. A formal perturbative solution
of the quantum Hamilton-Jacobi equation is given.Comment: 4 pages, RevTe
Free fields via canonical transformations of matter-coupled 2D dilaton gravity models
It is shown that the 1+1-dimensional matter-coupled Jackiw-Teitelboim model
and the model with an exponential potential can be converted by means of
appropriate canonical transformations into a bosonic string theory propagating
on a flat target space with an indefinite signature. This makes it possible to
consistently quantize these models in the functional Schroedinger
representation thus generalizing recent results on CGHS theory.Comment: 15 pages, Late
Correlation functions in super Liouville theory
We calculate three- and four-point functions in super Liouville theory
coupled to super Coulomb gas on world sheets with spherical topology. We first
integrate over the zero mode and assume that a parameter takes an integer
value. After calculating the amplitudes, we formally continue the parameter to
an arbitrary real number. Remarkably the result is completely parallel to the
bosonic case, the amplitudes being of the same form as those of the bosonic
case.Comment: 11 page
Domain Walls in a FRW Universe
We solve the equations of motion for a scalar field with domain wall boundary
conditions in a Friedmann-Robertson-Walker (FRW) spacetime. We find (in
agreement with Basu and Vilenkin) that no domain wall solutions exist in de
Sitter spacetime for h = H/m >= 1/2, where H is the Hubble parameter and m is
the scalar mass. In the general FRW case we develop a systematic perturbative
expansion in h to arrive at an approximate solution to the field equations. We
calculate the energy momentum tensor of the domain wall configuration, and show
that the energy density can become negative at the core of the defect for some
values of the non-minimal coupling parameter xi. We develop a translationally
invariant theory for fluctuations of the wall, obtain the effective Lagrangian
for these fluctuations, and quantize them using the Bunch-Davies vacuum in the
de Sitter case. Unlike previous analyses, we find that the fluctuations act as
zero-mass (as opposed to tachyonic) modes. This allows us to calculate the
distortion and the normal-normal correlators for the surface. The normal-normal
correlator decreases logarithmically with the distance between points for large
times and distances, indicating that the interface becomes rougher than in
Minkowski spacetime.Comment: 23 pages, LaTeX, 7 figures using epsf.tex. Now auto-generates P
On anomalies in classical dynamical systems
The definition of "classical anomaly" is introduced. It describes the
situation in which a purely classical dynamical system which presents both a
lagrangian and a hamiltonian formulation admits symmetries of the action for
which the Noether conserved charges, endorsed with the Poisson bracket
structure, close an algebra which is just the centrally extended version of the
original symmetry algebra. The consistency conditions for this to occur are
derived. Explicit examples are given based on simple two-dimensional models.
Applications of the above scheme and lines of further investigations are
suggested.Comment: arXiv version is already officia
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