24,542 research outputs found
BRST Analysis of the Supersymmetric Higher Spin Field Models
We develop the BRST approach for all massless integer and half-integer higher
spins in 4D Minkowski space, using the two component spinor nota- tion and
develop the Lagrangian formulation for supersymmetric higher spin models. It is
shown that the problem of second class constraints disappears and the BRST
procedure becomes much more simple than in tensorial nota- tion. Furthermore,
we demonstrate that the BRST procedure automatically provides extra auxiliary
components that belong in the set of supersymmetry auxiliary components.
Finally, we demonstrate how supersymmetry transfo- rmations are realized in
such an approach. As a result, we conclude that the BRST approach to higher
spin supersymmetric theories allows to derive both the Lagrangian and the
supersymmetry transformations. Although most part of the work is devoted to
massless component supersymmetric models, we also discuss generalization for
massive component supersymmetric models and for superfield models
The resource theory of quantum reference frames: manipulations and monotones
Every restriction on quantum operations defines a resource theory,
determining how quantum states that cannot be prepared under the restriction
may be manipulated and used to circumvent the restriction. A superselection
rule is a restriction that arises through the lack of a classical reference
frame and the states that circumvent it (the resource) are quantum reference
frames. We consider the resource theories that arise from three types of
superselection rule, associated respectively with lacking: (i) a phase
reference, (ii) a frame for chirality, and (iii) a frame for spatial
orientation. Focussing on pure unipartite quantum states (and in some cases
restricting our attention even further to subsets of these), we explore
single-copy and asymptotic manipulations. In particular, we identify the
necessary and sufficient conditions for a deterministic transformation between
two resource states to be possible and, when these conditions are not met, the
maximum probability with which the transformation can be achieved. We also
determine when a particular transformation can be achieved reversibly in the
limit of arbitrarily many copies and find the maximum rate of conversion. A
comparison of the three resource theories demonstrates that the extent to which
resources can be interconverted decreases as the strength of the restriction
increases. Along the way, we introduce several measures of frameness and prove
that these are monotonically nonincreasing under various classes of operations
that are permitted by the superselection rule.Comment: 37 pages, 4 figures, Published Versio
Constrained BRST- BFV Lagrangian formulations for Higher Spin Fields in Minkowski Spaces
BRST-BFV method for constrained Lagrangian formulations (LFs) for
(ir)reducible half-integer HS Poincare group representations in Minkowski space
is suggested. The procedure is derived by 2 ways: from the unconstrained
BRST-BFV method for mixed-symmetry HS fermionic fields subject to an arbitrary
Young tableaux with k rows (suggested in arXiv:1211.1273[hep-th]) by extracting
the second-class constraints, , from a total superalgebra of constraints, second, in
self-consistent way by means of finding BRST-extended initial off-shell
algebraic constraints, . In both cases, the latter constraints
supercommute on the constraint surface with constrained BRST and spin
operators . The closedness of the superalgebra guarantees that the final gauge-invariant LF is compatible with
off-shell constraints imposed on field and gauge parameter
vectors of Hilbert space not depending from the ghosts and conversion auxiliary
oscillators related to , in comparison with vectors for
unconstrained BRST-BFV LF. The suggested constrained BRST-BFV approach is valid
for both massive HS fields and integer HS fields in the second-order
formulation. It is shown that the respective constrained and unconstrained LFs
for (half)-integer HS fields with a given spin are equivalent. The constrained
Lagrangians in ghost-independent and component (for initial spin-tensor field)
are obtained and shown to coincide with Fang-Fronsdal formulation for
constrained totally-symmetric HS field. The triplet and unconstrained quartet
LFs for the latter field and gauge-invariant constrained Lagrangians for a
massive field of spin n+1/2 are derived. A concept of BRST-invariant
second-class constraints for a general dynamical system with mixed-class
constraints is suggested.Comment: 55 pages, typos corrected, published version; footnote 1 added, typo
in (3.15) correcte
The resource theory of informational nonequilibrium in thermodynamics
We review recent work on the foundations of thermodynamics in the light of
quantum information theory. We adopt a resource-theoretic perspective, wherein
thermodynamics is formulated as a theory of what agents can achieve under a
particular restriction, namely, that the only state preparations and
transformations that they can implement for free are those that are thermal at
some fixed temperature. States that are out of thermal equilibrium are the
resources. We consider the special case of this theory wherein all systems have
trivial Hamiltonians (that is, all of their energy levels are degenerate). In
this case, the only free operations are those that add noise to the system (or
implement a reversible evolution) and the only nonequilibrium states are states
of informational nonequilibrium, that is, states that deviate from the
maximally mixed state. The degree of this deviation we call the state's
nonuniformity; it is the resource of interest here, the fuel that is consumed,
for instance, in an erasure operation. We consider the different types of state
conversion: exact and approximate, single-shot and asymptotic, catalytic and
noncatalytic. In each case, we present the necessary and sufficient conditions
for the conversion to be possible for any pair of states, emphasizing a
geometrical representation of the conditions in terms of Lorenz curves. We also
review the problem of quantifying the nonuniformity of a state, in particular
through the use of generalized entropies. Quantum state conversion problems in
this resource theory can be shown to be always reducible to their classical
counterparts, so that there are no inherently quantum-mechanical features
arising in such problems. This body of work also demonstrates that the standard
formulation of the second law of thermodynamics is inadequate as a criterion
for deciding whether or not a given state transition is possible.Comment: 51 pages, 9 figures, Revised Versio
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