439 research outputs found
Partially gapped fermions in 2D
We compute mean field phase diagrams of two closely related interacting
fermion models in two spatial dimensions (2D). The first is the so-called 2D
t-t'-V model describing spinless fermions on a square lattice with local
hopping and density-density interactions. The second is the so-called 2D
Luttinger model that provides an effective description of the 2D t-t'-V model
and in which parts of the fermion degrees of freedom are treated exactly by
bosonization. In mean field theory, both models have a charge-density-wave
(CDW) instability making them gapped at half-filling. The 2D t-t'-V model has a
significant parameter regime away from half-filling where neither the CDW nor
the normal state are thermodynamically stable. We show that the 2D Luttinger
model allows to obtain more detailed information about this mixed region. In
particular, we find in the 2D Luttinger model a partially gapped phase that, as
we argue, can be described by an exactly solvable model.Comment: v1: 36 pages, 10 figures, v2: minor corrections; equation references
to arXiv:0903.0055 updated
Renormalization of Non-Commutative Phi^4_4 Field Theory in x Space
In this paper we provide a new proof that the Grosse-Wulkenhaar
non-commutative scalar Phi^4_4 theory is renormalizable to all orders in
perturbation theory, and extend it to more general models with covariant
derivatives. Our proof relies solely on a multiscale analysis in x space. We
think this proof is simpler and could be more adapted to the future study of
these theories (in particular at the non-perturbative or constructive level).Comment: 32 pages, v2: correction of lemmas 3.1 and 3.2 with no consequence on
the main resul
Singular factorizations, self-adjoint extensions, and applications to quantum many-body physics
We study self-adjoint operators defined by factorizing second order
differential operators in first order ones. We discuss examples where such
factorizations introduce singular interactions into simple quantum mechanical
models like the harmonic oscillator or the free particle on the circle. The
generalization of these examples to the many-body case yields quantum models of
distinguishable and interacting particles in one dimensions which can be solved
explicitly and by simple means. Our considerations lead us to a simple method
to construct exactly solvable quantum many-body systems of Calogero-Sutherland
type.Comment: 17 pages, LaTe
Transmission Lines in CMOS: An Explorative Study
On-chip transmission line modelling and design become increasingly important as frequencies are continuously going up. This paper explores possibilities to implement transmission lines on CMOS ICs via coupled coplanar strips. EM-field simulations with SONNET are used to estimate important transmission line properties like characteristic impedance, propagation velocity and loss in a 0.18 micron CMOS Technology. Both metal losses and substrate losses are modeled. Special attention is paid to the effect of the Silicon substrate, in particular to the so called “slow-wave mode” that can occur in the Si-SiO2 system
Leading Large N Modification of QCD_2 on a Cylinder by Dynamical Fermions
We consider 2-dimensional QCD on a cylinder, where space is a circle. We find
the ground state of the system in case of massless quarks in a expansion.
We find that coupling to fermions nontrivially modifies the large saddle
point of the gauge theory due to the phenomenon of `decompactification' of
eigenvalues of the gauge field. We calculate the vacuum energy and the vacuum
expectation value of the Wilson loop operator both of which show a nontrivial
dependence on the number of quarks flavours at the leading order in .Comment: 24 pages, TIFR-TH-94/3
Vanishing of Beta Function of Non Commutative Theory to all orders
The simplest non commutative renormalizable field theory, the model
on four dimensional Moyal space with harmonic potential is asymptotically safe
up to three loops, as shown by H. Grosse and R. Wulkenhaar, M. Disertori and V.
Rivasseau. We extend this result to all orders.Comment: 12 pages, 3 figure
BRST symmetry of SU(2) Yang-Mills theory in Cho--Faddeev--Niemi decomposition
We determine the nilpotent BRST and anti-BRST transformations for the
Cho--Faddeev-Niemi variables for the SU(2) Yang-Mills theory based on the new
interpretation given in the previous paper of the Cho--Faddeev-Niemi
decomposition. This gives a firm ground for performing the BRST quantization of
the Yang--Mills theory written in terms of the Cho--Faddeev-Niemi variables. We
propose also a modified version of the new Maximal Abelian gauge which could
play an important role in the reduction to the original Yang-Mills theory.Comment: 11 pages, no figure; Introduction improved, 3 references adde
Parametric Representation of Noncommutative Field Theory
In this paper we investigate the Schwinger parametric representation for the
Feynman amplitudes of the recently discovered renormalizable quantum
field theory on the Moyal non commutative space. This
representation involves new {\it hyperbolic} polynomials which are the
non-commutative analogs of the usual "Kirchoff" or "Symanzik" polynomials of
commutative field theory, but contain richer topological information.Comment: 31 pages,10 figure
Toroidal Soliton Solutions in O(3)^N Nonlinear Sigma Model
A set of N three component unit scalar fields in (3+1) Minkowski space-time
is investigated. The highly nonlinear coupling between them is chosen to omit
the scaling instabilities. The multi-soliton static configurations with
arbitrary Hopf numbers are found. Moreover, the generalized version of the
Vakulenko-Kapitansky inequality is obtained. The possibility of attractive,
repulsing and noninteracting channels is discussed.Comment: to be published in Mod. Phys. Lett.
Abelian Decomposition of Sp(2N) Yang-Mills Theory
In the previous paper, we generalized the method of Abelian decomposition to
the case of SO(N) Yang-Mills theory. This method that was proposed by Faddeev
and Niemi introduces a set of variables for describing the infrared limit of a
Yang-Mills theory. Here, we extend the decomposition method further to the
general case of four-dimensional Sp(2N) Yang-Mills theory. We find that the
Sp(2N) connection decomposes according to irreducible representations of SO(N).Comment: latex, 8 page
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