7,552 research outputs found
Method and device for the detection of phenol and related compounds
A method is described which permits the selective oxidation and potentiometric detection of phenol and related compounds in an electrochemical cell. An anode coated with a gel immobilized oxidative enzyme and a cathode are each placed in an electrolyte solution. The potential of the cell is measured by a potentiometer connected to the electrodes
Phase structure of an Abelian two-Higgs model and high temperature superconductors
We study the phase structure of a three dimensional Abelian Higgs model with
singly- and doubly-charged scalar fields coupled to a compact Abelian gauge
field. The model is pretending to describe systems of strongly correlated
electrons such as high-Tc superconductivity in overdoped regime and exotic
phases supporting excitations with fractionalized quantum numbers. We identify
the Fermi liquid, the spin gap, the superconductor and the strange metallic
phases in which densities and properties of holon and spinon vortices and
monopoles are explored. The phase diagram in the 3D coupling space is
predicted. We show that at sufficiently strong gauge coupling the spinon-pair
and holon condensation transitions merge together and become, unexpectedly,
first order.Comment: 5 pages, 9 figures, RevTeX
Improving the lattice axial vector current
For Wilson and clover fermions traditional formulations of the axial vector
current do not respect the continuum Ward identity which relates the divergence
of that current to the pseudoscalar density. Here we propose to use a
point-split or one-link axial vector current whose divergence exactly satisfies
a lattice Ward identity, involving the pseudoscalar density and a number of
irrelevant operators. We check in one-loop lattice perturbation theory with
SLiNC fermion and gauge plaquette action that this is indeed the case including
order effects. Including these operators the axial Ward identity remains
renormalisation invariant. First preliminary results of a nonperturbative check
of the Ward identity are also presented.Comment: 7 pages, 3 figures, Proceedings of the 33rd International Symposium
on Lattice Field Theory, 14-18 July 2015, Kobe, Japa
Renormalization of local quark-bilinear operators for Nf=3 flavors of SLiNC fermions
The renormalization factors of local quark-bilinear operators are computed
non-perturbatively for flavors of SLiNC fermions, with emphasis on the
various procedures for the chiral and continuum extrapolations. The simulations
are performed at a lattice spacing fm, and for five values of the
pion mass in the range of 290-465 MeV, allowing a safe and stable chiral
extrapolation. Emphasis is given in the subtraction of the well-known pion pole
which affects the renormalization factor of the pseudoscalar current. We also
compute the inverse propagator and the Green's functions of the local bilinears
to one loop in perturbation theory. We investigate lattice artifacts by
computing them perturbatively to second order as well as to all orders in the
lattice spacing. The renormalization conditions are defined in the RI-MOM
scheme, for both the perturbative and non-perturbative results. The
renormalization factors, obtained at different values of the renormalization
scale, are translated to the scheme and are evolved
perturbatively to 2 GeV. Any residual dependence on the initial renormalization
scale is eliminated by an extrapolation to the continuum limit. We also study
the various sources of systematic errors.
Particular care is taken in correcting the non-perturbative estimates by
subtracting lattice artifacts computed to one loop perturbation theory using
the same action. We test two different methods, by subtracting either the
contributions, or the complete (all orders in )
one-loop lattice artifacts.Comment: 33 pages, 27 figures, 6 table
The electric dipole moment of the neutron from 2+1 flavor lattice QCD
We compute the electric dipole moment d_n of the neutron from a fully
dynamical simulation of lattice QCD with 2+1 flavors of clover fermions and
nonvanishing theta term. The latter is rotated into the pseudoscalar density in
the fermionic action using the axial anomaly. To make the action real, the
vacuum angle theta is taken to be purely imaginary. The physical value of d_n
is obtained by analytic continuation. We find d_n = -3.8(2)(9) x 10^{-16}
[theta e cm], which, when combined with the experimental limit on d_n, leads to
the upper bound theta < 7.6 x 10^{-11}.Comment: 12 pages, 8 figures, matches PRL published versio
Toward a systematic 1/d expansion: Two particle properties
We present a procedure to calculate 1/d corrections to the two-particle
properties around the infinite dimensional dynamical mean field limit. Our
method is based on a modified version of the scheme of Ref.
onlinecite{SchillerIngersent}}. To test our method we study the Hubbard model
at half filling within the fluctuation exchange approximation (FLEX), a
selfconsistent generalization of iterative perturbation theory. Apart from the
inherent unstabilities of FLEX, our method is stable and results in causal
solutions. We find that 1/d corrections to the local approximation are
relatively small in the Hubbard model.Comment: 4 pages, 4 eps figures, REVTe
Determining the scale in Lattice QCD
We discuss scale setting in the context of 2+1 dynamical fermion simulations
where we approach the physical point in the quark mass plane keeping the
average quark mass constant. We have simulations at four beta values, and after
determining the paths and lattice spacings, we give an estimation of the
phenomenological values of various Wilson flow scales.Comment: 7 pages; talk presented at Lattice 2015, the 33rd International
Symposium on Lattice Field Theory 4 -18 July 2015 at Kobe International
Conference Center, Kobe, Japan; PoS(LATTICE2015)26
Wilson flow and scale setting from lattice QCD
We give a determination of the phenomenological value of the Wilson (or
gradient) flow scales t0 and w0 for 2+1 flavours of dynamical quarks. The
simulations are performed keeping the average quark mass constant, which allows
the approach to the physical point to be made in a controlled manner. O(a)
improved clover fermions are used and together with four lattice spacings this
allows the continuum extrapolation to be taken.Comment: 24 pages, 11 figure
The operator product expansion on the lattice
We investigate the Operator Product Expansion (OPE) on the lattice by
directly measuring the product (where J is the vector current) and
comparing it with the expectation values of bilinear operators. This will
determine the Wilson coefficients in the OPE from lattice data, and so give an
alternative to the conventional methods of renormalising lattice structure
function calculations. It could also give us access to higher twist quantities
such as the longitudinal structure function F_L = F_2 - 2 x F_1. We use overlap
fermions because of their improved chiral properties, which reduces the number
of possible operator mixing coefficients.Comment: 7 pages, 4 postscript figures. Contribution to Lattice 2007,
Regensbur
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