32 research outputs found
Screening in two-dimensional gauge theories
We analyze the problem of screening in 1+1 dimensional gauge theories. Using
QED2 as a warm-up for the non-abelian models we show the mechanism of the
string breaking, in particular the vanishing overlap of the Wilson loops to the
broken-string ground state that has been conjectured in higher-dimensional
analyses. We attempt to extend our analysis to non-integer charges in the
quenched and unquenched cases, in pursuit of the numerical check of a renowned
result for the string tension between arbitrarily-charged fermions in the
massive Schwinger model.Comment: 7 pages, 4 figures, proceedings of the XXX International Symposium on
Lattice Field Theory, Cairns, Australi
Preliminary study of two-dimensional SU(N) Yang-Mills theory with adjoint matter by Hybrid Monte Carlo approach
Two-dimensional non-abelian quantum field models provide a useful laboratory
for analytic and numerical investigations of quantum theories with gauge
symmetry. They can exhibit various features, such as charge confinement, which
are known from D=4 theories like QCD. Several analytic predictions concerning
the spectra of two-dimensional systems with adjoint matter were postulated and
numerical results were obtained using Discrete Light Cone Quantization
techniques, however none of them has been checked via Monte Carlo simulations.
In this Letter we present two such models which are particularly interesting
from the physical point of view and discuss first numerical results.Comment: 7 pages, proceedings of The XXIX International Symposium on Lattice
Field Theory, Squaw Valley, Lake Tahoe, Californi
Wilson loops with arbitrary charges
We discuss how to implement, in lattice gauge theories, external charges
which are not commensurate with an elementary gauge coupling. It is shown that
an arbitrary, real power of a standard Wilson loop (or Polyakov line) can be
defined and consistently computed in lattice formulation of non-abelian, two
dimensional gauge theories. However, such an observable can excite quantum
states with integer fluxes only. Since the non-integer fluxes are not in the
spectrum of the theory they cannot be created, no matter which observable is
chosen. Also the continuum limit of above averages does not exist unless the
powers in question are in fact integer. On the other hand, a new continuum
limit exists, which is rather intuitive, and where above observables make
perfect sense and lead to the string tension proportional to the square of
arbitrary (non necessary commensurate with gauge coupling) charge.Comment: 9 pages, 3 figure
HQET form factors for decays beyond leading order
We compute semi-leptonic decay form factors using Heavy Quark Effective
Theory on the lattice. To obtain good control of the expansion, one has
to take into account not only the leading static order but also the terms
arising at : kinetic, spin and current insertions. We show results
for these terms calculated through the ratio method, using our prior results
for the static order. After combining them with non-perturbative HQET
parameters they can be continuum-extrapolated to give the QCD form factor
correct up to corrections and without
corrections.Comment: 7 pages, 4 figures. Proceedings of the 35th International Symposium
on Lattice Field Theory, 18-24 June 2017, Granada, Spain; v2: small
corrections, published versio
Glueball masses in 2+1 dimensional SU(N) gauge theories with twisted boundary conditions
We analyze 2+1 dimensional Yang-Mills theory regularized on a lattice with
twisted boundary conditions in the spatial directions. In previous work it was
shown that the observables in the non-zero electric flux sectors obey the
so-called -scaling, i.e. depend only on the dimensionless variable and the angle given by the parameters of the twist (
being the length of the spatial torus and the inverse 't Hooft coupling).
It is conjectured that this scaling is obeyed by all physical quantities. In
this work we extend the previous analyses to the zero electric flux (glueball)
sector. We study the mass of the lightest scalar glueball in two theories with
different but matching and in a wide range of couplings
from the perturbative small-volume regime to the non-perturbative one. We find
that the results are consistent with the -scaling hypothesis.Comment: 7 pages, contribution to the 32nd International Symposium on Lattice
Field Theory, 23-28 June, 2014. Columbia University New York, NY; v2:
references added, minor changes; PoS(LATTICE2014)05
First passage times for subordinate Brownian motions
Let X_t be a subordinate Brownian motion, and suppose that the Levy measure
of the underlying subordinator has completely monotone density. Under very mild
conditions, we find integral formulae for the tail distribution P(\tau_x > t)
of first passage times \tau_x through a barrier at x > 0, and its derivatives
in t. As a corollary, we examine the asymptotic behaviour of P(\tau_x > t) and
its t-derivatives, either as t goes to infinity or x goes to 0.Comment: 24 pages, 1 figur