179 research outputs found
Modified convex hull pricing for fixed load power markets
We consider fixed load power market with non-convexities originating from
start-up and no-load costs of generators. The convex hull (minimal uplift)
pricing method results in power prices minimizing the total uplift payments to
generators, which compensate their potential profits lost by accepting
centralized dispatch solution, treating as foregone all opportunities to supply
any other output volume allowed by generator internal constraints. For each
generator we define a set of output volumes, which are economically and
technologically feasible in the absence of centralized dispatch, and propose to
exclude output volumes outside the set from lost profit calculations. New
pricing method results in generally different set of market prices and lower
(or equal) total uplift payment compared to convex hull pricing algorithm.Comment: v.3 (section on comparison with convex hull pricing extended,
references added
Construction of Lagrangian local symmetries for general quadratic theory
We propose a procedure which allows one to construct local symmetry
generators of general quadratic Lagrangian theory. Manifest recurrence
relations for generators in terms of so-called structure matrices of the Dirac
formalism are obtained. The procedure fulfilled in terms of initial variables
of the theory, and do not implies either separation of constraints on first and
second class subsets or any other choice of basis for constraints
Improved extended Hamiltonian and search for local symmetries
We analyze a structure of the singular Lagrangian with first and second
class constraints of an arbitrary stage. We show that there exist an equivalent
Lagrangian (called the extended Lagrangian ) that generates all the
original constraints on second stage of the Dirac-Bergmann procedure. The
extended Lagrangian is obtained in closed form through the initial one. The
formalism implies an extension of the original configuration space by auxiliary
variables. Some of them are identified with gauge fields supplying local
symmetries of . As an application of the formalism, we found closed
expression for the gauge generators of through the first class
constraints. It turns out to be much more easy task as those for . All the
first class constraints of turn out to be the gauge symmetry generators of
. By this way, local symmetries of with higher order derivatives
of the local parameters decompose into a sum of the gauge symmetries of . It proves the Dirac conjecture in the Lagrangian framework
Monopole operators in three-dimensional N=4 SYM and mirror symmetry
We study non-abelian monopole operators in the infrared limit of
three-dimensional SU(N_c) and N=4 SU(2) gauge theories. Using large N_f
expansion and operator-state isomorphism of the resulting superconformal field
theories, we construct monopole operators which are (anti-)chiral primaries and
compute their charges under the global symmetries. Predictions of
three-dimensional mirror symmetry for the quantum numbers of these monopole
operators are verified.Comment: 23 pages, LaTex; v2: section 3.4 modified, section 3.5 extended,
references adde
Generalization of the Extended Lagrangian Formalism on a Field Theory and Applications
Formalism of extended Lagrangian represent a systematic procedure to look for
the local symmetries of a given Lagrangian action. In this work, the formalism
is discussed and applied to a field theory. We describe it in detail for a
field theory with first-class constraints present in the Hamiltonian
formulation. The method is illustrated on examples of electrodynamics,
Yang-Mills field and non-linear sigma model.Comment: 17 pages, to be published in Phys. Rev.
Monopole Quantum Numbers in the Staggered Flux Spin Liquid
Algebraic spin liquids, which are exotic gapless spin states preserving all
microscopic symmetries, have been widely studied due to potential realizations
in frustrated quantum magnets and the cuprates. At low energies, such putative
phases are described by quantum electrodynamics in 2+1 dimensions. While
significant progress has been made in understanding this nontrivial interacting
field theory and the associated spin physics, one important issue which has
proved elusive is the quantum numbers carried by so-called monopole operators.
Here we address this issue in the ``staggered-flux'' spin liquid which may be
relevant to the pseudogap regime in high-T_c. Employing general analytical
arguments supported by simple numerics, we argue that proximate phases encoded
in the monopole operators include the familiar Neel and valence bond solid
orders, as well as other symmetry-breaking orders closely related to those
previously explored in the monopole-free sector of the theory. Surprisingly, we
also find that one monopole operator carries trivial quantum numbers, and
briefly discuss its possible implications.Comment: 9 pages, 0 figures; minor clarification
Algebraic spin liquid as the mother of many competing orders
We study the properties of a class of two-dimensional interacting critical
states -- dubbed algebraic spin liquids -- that can arise in two-dimensional
quantum magnets. A particular example that we focus on is the staggered flux
spin liquid, which plays a key role in some theories of underdoped cuprate
superconductors. We show that the low-energy theory of such states has much
higher symmetry than the underlying microscopic spin system. This symmetry has
remarkable consequences, leading in particular to the unification of a number
of seemingly unrelated competing orders. The correlations of these orders --
including, in the staggered flux state, the Neel vector and the order parameter
for the columnar and box valence-bond solid states -- all exhibit the SAME slow
power-law decay. Implications for experiments in the pseudogap regime of the
cuprates and for numerical calculations on model systems are discussed.Comment: Minor changes; final published version. 17 pages, 3 figure
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