208 research outputs found
Loop groups, anyons and the Calogero-Sutherland model
The positive energy representations of the loop group of U(1) are used to
construct a boson-anyon correspondence. We compute all the correlation
functions of our anyon fields and study an anyonic W-algebra of unbounded
operators with a common dense domain. This algebra contains an operator with
peculiar exchange relations with the anyon fields. This operator can be
interpreted as a second quantised Calogero-Sutherland (CS) Hamiltonian and may
be used to solve the CS model. In particular, we inductively construct all
eigenfunctions of the CS model from anyon correlation functions, for all
particle numbers and positive couplings.Comment: 34 pages, Late
The oscillation valve in the transmission and reception of radio messages
This item was digitized by the Internet Archive. Thesis (M.A.)--Boston Universityhttps://archive.org/details/theoscillationva00ken
Ionic Liquid Based Polymer Gel Electrolytes for Use with Germanium Thin Film Anodes in Lithium Ion Batteries
Thermally stable, flexible polymer gel electrolytes with high ionic conductivity are prepared by mixing the ionic liquid 1âbutylâ1âmethylpyrrolidinium bis(trifluoromethylsulfonyl)imide (C4mpyrTFSI), LiTFSI and poly(vinylidene difluorideâcoâhexafluoropropylene (PVDFâHFP). FTâIR and Raman spectroscopy show that an amorphous film is obtained for high (60â%) C4mpyrTFSI contents. Thermogravimetric analysis (TGA) confirms that the polymer gels are stable below âŒ300â°C in both nitrogen and air environments. Ionic conductivity of 1.9Ă10â3â
Sâcmâ2 at room temperature is achieved for the 60â% ionic liquid loaded gel. Germanium (Ge) anodes maintain a coulombic efficiency above 95â% after 90 cycles in potential cycling tests with the 60â% C4mpyrTFSI polymer gel
Gribov ambiguity and non-trivial vacuum structure of gauge theories on a cylinder
Using the hamiltonian framework, we analyze the Gribov problem for U(N) and
SU(N) gauge theories on a cylinder (= (1+1) dimensional spacetime with compact
space S^1). The space of gauge orbits is found to be an orbifold. We show by
explicit construction that a proper treatment of the Gribov ambiguity leads to
a highly non-trivial structure of all physical states in these quantum field
theory models. The especially interesting example of massless QCD is discussed
in more detail: There, some of the special static gauge transformations which
are responsible for the Gribov ambiguity also lead to a spectral flow, and this
implies a chiral condensate in all physical states. We also show that the
latter is closely related to the Schwinger term and the chiral anomaly.Comment: 13 pages, a few typos and signs corrected, reference adde
Very Large Array Observations of Ammonia in Infrared-Dark Clouds II: Internal Kinematics
Infrared-dark clouds (IRDCs) are believed to be the birthplaces of rich
clusters and thus contain the earliest phases of high-mass star formation. We
use the Green Bank Telescope (GBT) and Very Large Array (VLA) maps of ammonia
(NH3) in six IRDCs to measure their column density and temperature structure
(Paper 1), and here, we investigate the kinematic structure and energy content.
We find that IRDCs overall display organized velocity fields, with only
localized disruptions due to embedded star formation. The local effects seen in
NH3 emission are not high velocity outflows but rather moderate (few km/s)
increases in the line width that exhibit maxima near or coincident with the
mid-infrared emission tracing protostars. These line width enhancements could
be the result of infall or (hidden in NH3 emission) outflow. Not only is the
kinetic energy content insufficient to support the IRDCs against collapse, but
also the spatial energy distribution is inconsistent with a scenario of
turbulent cloud support. We conclude that the velocity signatures of the IRDCs
in our sample are due to active collapse and fragmentation, in some cases
augmented by local feedback from stars.Comment: 15 pages, 12 figures, accepted for publication in Ap
Chiral Schwinger models without gauge anomalies
We find a large class of quantum gauge models with massless fermions where
the coupling to the gauge fields is not chirally symmetric and which
nevertheless do not suffer from gauge anomalies. To be specific we study two
dimensional Abelian models in the Hamiltonian framework which can be
constructed and solved by standard techniques. The general model describes
\Np photon fields and \Nf flavors of Dirac fermions with 2\Nf\Np
different coupling constants i.e. the chiral component of each fermion can be
coupled to the gauge fields differently. We construct these models and find
conditions so that no gauge anomaly appears. If these conditions hold it is
possible to construct and solve the model explicitly, so that gauge- and
Lorentz invariance are manifest.Comment: 18 page
QCD(1+1) with massless quarks and gauge covariant Sugawara construction
We use the Hamiltonian framework to study massless QCD, i.e.\
Yang-Mills gauge theories with massless Dirac fermions on a cylinder (= (1+1)
dimensional spacetime ) and make explicite the full,
non-perturbative structure of these quantum field theory models. We consider
fermion flavors and gauge group either \U(N_C), \SU(N_C) or another
Lie subgroup of \U(N_C). In this approach, anomalies are traced back to
kinematical requirements such as positivity of the Hamiltonian, gauge
invariance, and the condition that all observables are represented by
well-defined operators on a Hilbert space. We also give equal time commutators
of the energy momentum tensor and find a gauge-covariant form of the (affine-)
Sugawara construction. This allows us to represent massless QCD as a
gauge theory of Kac-Moody currents and prove its equivalence to a gauged
Wess-Zumino-Witten model with a dynamical Yang-Mills field.Comment: 11 pages, ESI 110 Minor changes (including title); version to appear
in Phys. Lett.
Exact solution of a 2D interacting fermion model
We study an exactly solvable quantum field theory (QFT) model describing
interacting fermions in 2+1 dimensions. This model is motivated by physical
arguments suggesting that it provides an effective description of spinless
fermions on a square lattice with local hopping and density-density
interactions if, close to half filling, the system develops a partial energy
gap. The necessary regularization of the QFT model is based on this proposed
relation to lattice fermions. We use bosonization methods to diagonalize the
Hamiltonian and to compute all correlation functions. We also discuss how,
after appropriate multiplicative renormalizations, all short- and long distance
cutoffs can be removed. In particular, we prove that the renormalized two-point
functions have algebraic decay with non-trivial exponents depending on the
interaction strengths, which is a hallmark of Luttinger-liquid behavior.Comment: 59 pages, 3 figures, v2: further references added; additional
subsections elaborating mathematical details; additional appendix with
details on the relation to lattice fermion
Ionic liquid based polymer gel electrolytes for use with germanium thin film anodes in lithium ion batteries
Thermally stable, flexible polymer gel electrolytes with high ionic conductivity are prepared by mixing the ionic liquid 1âbutylâ1âmethylpyrrolidinium bis(trifluoromethylsulfonyl)imide (C4mpyrTFSI), LiTFSI and poly(vinylidene difluorideâcoâhexafluoropropylene (PVDFâHFP). FTâIR and Raman spectroscopy show that an amorphous film is obtained for high (60â%) C4mpyrTFSI contents. Thermogravimetric analysis (TGA) confirms that the polymer gels are stable below âŒ300â°C in both nitrogen and air environments. Ionic conductivity of 1.9Ă10â3 Sâcmâ2 at room temperature is achieved for the 60â% ionic liquid loaded gel. Germanium (Ge) anodes maintain a coulombic efficiency above 95â% after 90 cycles in potential cycling tests with the 60â% C4mpyrTFSI polymer gel
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