138 research outputs found
Generalized Supersymmetric Quantum Mechanics and Reflectionless Fermion Bags in 1+1 Dimensions
We study static fermion bags in the 1+1 dimensional Gross-Neveu and
Nambu-Jona-Lasinio models. It has been known, from the work of Dashen,
Hasslacher and Neveu (DHN), followed by Shei's work, in the 1970's, that the
self-consistent static fermion bags in these models are reflectionless. The
works of DHN and of Shei were based on inverse scattering theory. Several years
ago, we offered an alternative argument to establish the reflectionless nature
of these fermion bags, which was based on analysis of the spatial asymptotic
behavior of the resolvent of the Dirac operator in the background of a static
bag, subjected to the appropriate boundary conditions. We also calculated the
masses of fermion bags based on the resolvent and the Gelfand-Dikii identity.
Based on arguments taken from a certain generalized one dimensional
supersymmetric quantum mechanics, which underlies the spectral theory of these
Dirac operators, we now realize that our analysis of the asymptotic behavior of
the resolvent was incomplete. We offer here a critique of our asymptotic
argument.Comment: 33 pages, 2 figure
Dynamical Generation of Extended Objects in a Dimensional Chiral Field Theory: Non-Perturbative Dirac Operator Resolvent Analysis
We analyze the dimensional Nambu-Jona-Lasinio model non-perturbatively.
In addition to its simple ground state saddle points, the effective action of
this model has a rich collection of non-trivial saddle points in which the
composite fields \sigx=\lag\bar\psi\psi\rag and \pix=\lag\bar\psi
i\gam_5\psi\rag form static space dependent configurations because of
non-trivial dynamics. These configurations may be viewed as one dimensional
chiral bags that trap the original fermions (``quarks") into stable extended
entities (``hadrons"). We provide explicit expressions for the profiles of
these objects and calculate their masses. Our analysis of these saddle points
is based on an explicit representation we find for the diagonal resolvent of
the Dirac operator in a \{\sigx, \pix\} background which produces a
prescribed number of bound states. We analyse in detail the cases of a single
as well as two bound states. We find that bags that trap fermions are the
most stable ones, because they release all the fermion rest mass as binding
energy and become massless. Our explicit construction of the diagonal resolvent
is based on elementary Sturm-Liouville theory and simple dimensional analysis
and does not depend on the large approximation. These facts make it, in our
view, simpler and more direct than the calculations previously done by Shei,
using the inverse scattering method following Dashen, Hasslacher, and Neveu.
Our method of finding such non-trivial static configurations may be applied to
other dimensional field theories
Does the complex deformation of the Riemann equation exhibit shocks?
The Riemann equation , which describes a one-dimensional
accelerationless perfect fluid, possesses solutions that typically develop
shocks in a finite time. This equation is \cP\cT symmetric. A one-parameter
\cP\cT-invariant complex deformation of this equation,
( real), is solved exactly using the
method of characteristic strips, and it is shown that for real initial
conditions, shocks cannot develop unless is an odd integer.Comment: latex, 8 page
On Kinks and Bound States in the Gross-Neveu Model
We investigate static space dependent \sigx=\lag\bar\psi\psi\rag saddle
point configurations in the two dimensional Gross-Neveu model in the large N
limit. We solve the saddle point condition for \sigx explicitly by employing
supersymmetric quantum mechanics and using simple properties of the diagonal
resolvent of one dimensional Schr\"odinger operators rather than inverse
scattering techniques. The resulting solutions in the sector of unbroken
supersymmetry are the Callan-Coleman-Gross-Zee kink configurations. We thus
provide a direct and clean construction of these kinks. In the sector of broken
supersymmetry we derive the DHN saddle point configurations. Our method of
finding such non-trivial static configurations may be applied also in other two
dimensional field theories.Comment: Revised version. A new section added with derivation of the DHN
static configurations in the sector of broken supersymmetry. Some references
added as well. 25 pp, latex, e-mail [email protected]
Renormalizing Rectangles and Other Topics in Random Matrix Theory
We consider random Hermitian matrices made of complex or real
rectangular blocks, where the blocks are drawn from various ensembles. These
matrices have pairs of opposite real nonvanishing eigenvalues, as well as
zero eigenvalues (for .) These zero eigenvalues are ``kinematical"
in the sense that they are independent of randomness. We study the eigenvalue
distribution of these matrices to leading order in the large limit, in
which the ``rectangularity" is held fixed. We apply a variety of
methods in our study. We study Gaussian ensembles by a simple diagrammatic
method, by the Dyson gas approach, and by a generalization of the Kazakov
method. These methods make use of the invariance of such ensembles under the
action of symmetry groups. The more complicated Wigner ensemble, which does not
enjoy such symmetry properties, is studied by large renormalization
techniques. In addition to the kinematical -function spike in the
eigenvalue density which corresponds to zero eigenvalues, we find for both
types of ensembles that if is held fixed as , the
non-zero eigenvalues give rise to two separated lobes that are located
symmetrically with respect to the origin. This separation arises because the
non-zero eigenvalues are repelled macroscopically from the origin. Finally, we
study the oscillatory behavior of the eigenvalue distribution near the
endpoints of the lobes, a behavior governed by Airy functions. As the lobes come closer, and the Airy oscillatory behavior near the endpoints
that are close to zero breaks down. We interpret this breakdown as a signal
that drives a cross over to the oscillation governed by Bessel
functions near the origin for matrices made of square blocks.Comment: LateX, 34 pages, 3 ps figure
"Single Ring Theorem" and the Disk-Annulus Phase Transition
Recently, an analytic method was developed to study in the large limit
non-hermitean random matrices that are drawn from a large class of circularly
symmetric non-Gaussian probability distributions, thus extending the existing
Gaussian non-hermitean literature. One obtains an explicit algebraic equation
for the integrated density of eigenvalues from which the Green's function and
averaged density of eigenvalues could be calculated in a simple manner. Thus,
that formalism may be thought of as the non-hermitean analog of the method due
to Br\'ezin, Itzykson, Parisi and Zuber for analyzing hermitean non-Gaussian
random matrices. A somewhat surprising result is the so called "Single Ring"
theorem, namely, that the domain of the eigenvalue distribution in the complex
plane is either a disk or an annulus. In this paper we extend previous results
and provide simple new explicit expressions for the radii of the eigenvalue
distiobution and for the value of the eigenvalue density at the edges of the
eigenvalue distribution of the non-hermitean matrix in terms of moments of the
eigenvalue distribution of the associated hermitean matrix. We then present
several numerical verifications of the previously obtained analytic results for
the quartic ensemble and its phase transition from a disk shaped eigenvalue
distribution to an annular distribution. Finally, we demonstrate numerically
the "Single Ring" theorem for the sextic potential, namely, the potential of
lowest degree for which the "Single Ring" theorem has non-trivial consequences.Comment: latex, 5 eps figures, 41 page
Non-Hermitean Random Matrix Theory: method of hermitization
We consider random non-hermitean matrices in the large limit. The power
of analytic function theory cannot be brought to bear directly to analyze
non-hermitean random matrices, in contrast to hermitean random matrices. To
overcome this difficulty, we show that associated to each ensemble of
non-hermitean matrices there is an auxiliary ensemble of random hermitean
matrices which can be analyzed by the usual methods. We then extract the
Green's function and the density of eigenvalues of the non-hermitean ensemble
from those of the auxiliary ensemble. We apply this "method of hermitization"
to several examples, and discuss a number of related issues.Comment: 46 pages, 3 ps figures, LaTe
Non-Gaussian Non-Hermitean Random Matrix Theory: phase transitions and addition formalism
We apply the recently introduced method of hermitization to study in the
large limit non-hermitean random matrices that are drawn from a large class
of circularly symmetric non-Gaussian probability distributions, thus extending
the recent Gaussian non-hermitean literature. We develop the general formalism
for calculating the Green's function and averaged density of eigenvalues, which
may be thought of as the non-hermitean analog of the method due to Br\`ezin,
Itzykson, Parisi and Zuber for analyzing hermitean non-Gaussian random
matrices. We obtain an explicit algebraic equation for the integrated density
of eigenvalues. A somewhat surprising result of that equation is that the shape
of the eigenvalue distribution in the complex plane is either a disk or an
annulus. As a concrete example, we analyze the quartic ensemble and study the
phase transition from a disk shaped eigenvalue distribution to an annular
distribution. Finally, we apply the method of hermitization to develop the
addition formalism for free non-hermitean random variables. We use this
formalism to state and prove a non-abelian non-hermitean version of the central
limit theorem.Comment: 40 pages, no figures, LaTex. Section 5 has been correcte
The Response to a Perturbation in the Reflection Amplitude
We apply inverse scattering theory to calculate the functional derivative of
the potential and wave function of a one-dimensional
Schr\"odinger operator with respect to the reflection amplitude .Comment: 16 pages, no figure
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