216 research outputs found
Gauge-Invariant Coordinates on Gauge-Theory Orbit Space
A gauge-invariant field is found which describes physical configurations,
i.e. gauge orbits, of non-Abelian gauge theories. This is accomplished with
non-Abelian generalizations of the Poincare'-Hodge formula for one-forms. In a
particular sense, the new field is dual to the gauge field. Using this field as
a coordinate, the metric and intrinsic curvature are discussed for Yang-Mills
orbit space for the (2+1)- and (3+1)-dimensional cases. The sectional, Ricci
and scalar curvatures are all formally non-negative. An expression for the new
field in terms of the Yang-Mills connection is found in 2+1 dimensions. The
measure on Schroedinger wave functionals is found in both 2+1 and 3+1
dimensions; in the former case, it resembles Karabali, Kim and Nair's measure.
We briefly discuss the form of the Hamiltonian in terms of the dual field and
comment on how this is relevant to the mass gap for both the (2+1)- and
(3+1)-dimensional cases.Comment: Typos corrected, more about the non-Abelian decomposition and inner
products, more discussion of the mass gap in 3+1 dimensions. Now 23 page
Beyond the String Genus
In an earlier work we used a path integral analysis to propose a higher genus
generalization of the elliptic genus. We found a cobordism invariant
parametrized by Teichmuller space. Here we simplify the formula and study the
behavior of our invariant under the action of the mapping class group of the
Riemann surface. We find that our invariant is a modular function with
multiplier just as in genus one.Comment: 40 pages, 1 figur
The supersymmetric sigma model and the geometry of the Weyl-Kac character formula
Field theoretic and geometric ideas are used to construct a chiral
supersymmetric field theory whose ground state is a specified irreducible
representation of a centrally extended loop group. The character index of the
associated supercharge (an appropriate Dirac operator on ) is the
Weyl-K\v{a}c character formula which we compute explicitly by the steepest
descent approximation.Comment: 40 page
The fundamental gap of simplices
The fundamental gap conjecture was recently proven by Andrews and
Clutterbuck: for any convex domain in normalized to have unit diameter,
the difference between the first two Dirichlet eigenvalues of the Laplacian is
bounded below by that of the interval. In this work, we focus on the moduli
spaces of simplices in all dimensions, and later specialize to the moduli space
of Euclidean triangles. Our first theorem is a compactness result for the gap
function on the moduli space of simplices in any dimension. Our second main
result verifies a recent conjecture of Antunes-Freitas: for any Euclidean
triangle normalized to have unit diameter, the fundamental gap is uniquely
minimized by the equilateral triangle.Comment: Final version, Journal ref adde
A study of the zero modes of the Faddeev-Popov operator in Euclidean Yang-Mills theories in the Landau gauge in d=2,3,4 dimensions
Examples of normalizable zero modes of the Faddeev-Popov operator in SU(2)
Euclidean Yang-Mills theories in the Landau gauge are constructed in d=2,3,4
dimensions.Comment: 18 pages. Text modifications. References added. Version accepted for
publication in the EPJ
Gauge equivalence in QCD: the Weyl and Coulomb gauges
The Weyl-gauge ( QCD Hamiltonian is unitarily transformed to a
representation in which it is expressed entirely in terms of gauge-invariant
quark and gluon fields. In a subspace of gauge-invariant states we have
constructed that implement the non-Abelian Gauss's law, this unitarily
transformed Weyl-gauge Hamiltonian can be further transformed and, under
appropriate circumstances, can be identified with the QCD Hamiltonian in the
Coulomb gauge. We demonstrate an isomorphism that materially facilitates the
application of this Hamiltonian to a variety of physical processes, including
the evaluation of -matrix elements. This isomorphism relates the
gauge-invariant representation of the Hamiltonian and the required set of
gauge-invariant states to a Hamiltonian of the same functional form but
dependent on ordinary unconstrained Weyl-gauge fields operating within a space
of ``standard'' perturbative states. The fact that the gauge-invariant
chromoelectric field is not hermitian has important implications for the
functional form of the Hamiltonian finally obtained. When this nonhermiticity
is taken into account, the ``extra'' vertices in Christ and Lee's Coulomb-gauge
Hamiltonian are natural outgrowths of the formalism. When this nonhermiticity
is neglected, the Hamiltonian used in the earlier work of Gribov and others
results.Comment: 25 page
Gauge Orbit Types for Theories with Classical Compact Gauge Group
We determine the orbit types of the action of the group of local gauge
transformations on the space of connections in a principal bundle with
structure group O(n), SO(n) or over a closed, simply connected manifold
of dimension 4. Complemented with earlier results on U(n) and SU(n) this
completes the classification of the orbit types for all classical compact gauge
groups over such space-time manifolds. On the way we derive the classification
of principal bundles with structure group SO(n) over these manifolds and the
Howe subgroups of SO(n).Comment: 57 page
Analytic and Reidemeister torsion for representations in finite type Hilbert modules
For a closed Riemannian manifold we extend the definition of analytic and
Reidemeister torsion associated to an orthogonal representation of fundamental
group on a Hilbert module of finite type over a finite von Neumann algebra. If
the representation is of determinant class we prove, generalizing the
Cheeger-M\"uller theorem, that the analytic and Reidemeister torsion are equal.
In particular, this proves the conjecture that for closed Riemannian manifolds
with positive Novikov-Shubin invariants, the L2 analytic and Reidemeister
torsions are equal.Comment: 78 pages, AMSTe
Towards Solving QCD - The Transverse Zero Modes in Light-Cone Quantization
We formulate QCD in (d+1) dimensions using Dirac's front form with periodic
boundary conditions, that is, within Discretized Light-Cone Quantization. The
formalism is worked out in detail for SU(2) pure glue theory in (2+1)
dimensions which is approximated by restriction to the lowest {\it transverse}
momentum gluons. The dimensionally-reduced theory turns out to be SU(2) gauge
theory coupled to adjoint scalar matter in (1+1) dimensions. The scalar field
is the remnant of the transverse gluon. This field has modes of both non-zero
and zero {\it longitudinal} momentum. We categorize the types of zero modes
that occur into three classes, dynamical, topological, and constrained, each
well known in separate contexts. The equation for the constrained mode is
explicitly worked out. The Gauss law is rather simply resolved to extract
physical, namely color singlet states. The topological gauge mode is treated
according to two alternative scenarios related to the In the one, a spectrum is
found consistent with pure SU(2) gluons in (1+1) dimensions. In the other, the
gauge mode excitations are estimated and their role in the spectrum with
genuine Fock excitations is explored. A color singlet state is given which
satisfies Gauss' law. Its invariant mass is estimated and discussed in the
physical limit.Comment: LaTex document, 26 pages, one figure (obtainable by contacting
authors). To appear in Physical. Review
Accessing directly the properties of fundamental scalars in the confinement and Higgs phase
The properties of elementary particles are encoded in their respective
propagators and interaction vertices. For a SU(2) gauge theory coupled to a
doublet of fundamental complex scalars these propagators are determined in both
the Higgs phase and the confinement phase and compared to the Yang-Mills case,
using lattice gauge theory. Since the propagators are gauge-dependent, this is
done in the Landau limit of 't Hooft gauge, permitting to also determine the
ghost propagator. It is found that neither the gauge boson nor the scalar
differ qualitatively in the different cases. In particular, the gauge boson
acquires a screening mass, and the scalar's screening mass is larger than the
renormalized mass. Only the ghost propagator shows a significant change.
Furthermore, indications are found that the consequences of the residual
non-perturbative gauge freedom due to Gribov copies could be different in the
confinement and the Higgs phase.Comment: 11 pages, 6 figures, 1 table; v2: one minor error corrected; v3: one
appendix on systematic uncertainties added and some minor changes, version to
appear in EPJ
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