454 research outputs found
Localization and symmetries
The violation of the Noether relation between symmetries and charges is
reduced to the time dependence of the charge associated to a conserved current.
For the U(1) gauge symmetry a non-perturbative control of the charge
commutators is obtained by an analysis of the Coulomb charged fields. From
this, in the unbroken case we obtain a correct expression for the electric
charge on the Coulomb states, its superselection and the presence of massless
vector bosons; in the broken case, we obtain a general non-perturbative version
of the Higgs phenomenon, i.e. the absence of massless Goldstone bosons and of
massless vector bosons. The conservation of the (gauge dependent) current
associated to the U(1) axial symmetry in QCD is shown to be compatible with the
time dependence of the corresponding charge commutators and a non-vanishing
eta' mass, as a consequence of the non locality of the (conserved) current.Comment: Invited contribution to ``The Quantum Universe'', dedicated to G.
Ghirardi for his 70th birthda
No Eigenvalue in Finite Quantum Electrodynamics
We re-examine Quantum Electrodynamics (QED) with massless electron as a
finite quantum field theory as advocated by Gell-Mann-Low, Baker-Johnson,
Adler, Jackiw and others. We analyze the Dyson-Schwinger equation satisfied by
the massless electron in finite QED and conclude that the theory admits no
nontrivial eigenvalue for the fine structure constant.Comment: 13 pages, Late
Spectral stochastic processes arising in quantum mechanical models with a non-L2 ground state
A functional integral representation is given for a large class of quantum
mechanical models with a non--L2 ground state. As a prototype the particle in a
periodic potential is discussed: a unique ground state is shown to exist as a
state on the Weyl algebra, and a functional measure (spectral stochastic
process) is constructed on trajectories taking values in the spectrum of the
maximal abelian subalgebra of the Weyl algebra isomorphic to the algebra of
almost periodic functions. The thermodynamical limit of the finite volume
functional integrals for such models is discussed, and the superselection
sectors associated to an observable subalgebra of the Weyl algebra are
described in terms of boundary conditions and/or topological terms in the
finite volume measures.Comment: 15 pages, Plain Te
Remarks on some new models of interacting quantum fields with indefinite metric
We study quantum field models in indefinite metric. We introduce the modified
Wightman axioms of Morchio and Strocchi as a general framework of indefinite
metric quantum field theory (QFT) and present concrete interacting relativistic
models obtained by analytical continuation from some stochastic processes with
Euclidean invariance. As a first step towards scattering theory in indefinite
metric QFT, we give a proof of the spectral condition on the translation group
for the relativistic models.Comment: 13 page
Massless scalar field in two-dimensional de Sitter universe
We study the massless minimally coupled scalar field on a two--dimensional de
Sitter space-time in the setting of axiomatic quantum field theory. We
construct the invariant Wightman distribution obtained as the renormalized
zero--mass limit of the massive one. Insisting on gauge invariance of the model
we construct a vacuum state and a Hilbert space of physical states which are
invariant under the action of the whole de Sitter group. We also present the
integral expression of the conserved charge which generates the gauge
invariance and propose a definition of dual field.Comment: 13 page
Topological mass mechanism and exact fields mapping
We present a class of mappings between models with topological mass mechanism
and purely topological models in arbitrary dimensions. These mappings are
established by directly mapping the fields of one model in terms of the fields
of the other model in closed expressions. These expressions provide the
mappings of their actions as well as the mappings of their propagators. For a
general class of models in which the topological model becomes the BF model the
mappings present arbitrary functions which otherwise are absent for
Chern-Simons like actions. This work generalizes the results of [1] for
arbitrary dimensions.Comment: 11 page
Mathematical structure of the temporal gauge
The mathematical structure of the temporal gauge of QED is critically
examined in both the alternative formulations characterized by either
positivity or regularity of the Weyl algebra. The conflict between time
translation invariance and Gauss law constraint is shown to lead to peculiar
features. In the positive case only the correlations of exponentials of fields
exist (non regularity), the space translations are not strongly continuous, so
that their generators do not exist, a theta vacuum degeneracy occurs,
associated to a spontaneous symmetry breaking. In the indefinite case the
spectral condition only holds in terms of positivity of the energy, gauge
invariant theta-vacua exist on the observables, with no extension to time
translation invariant states on the field algebra, the vacuum is faithful on
the longitudinal algebra and a KMS structure emerges. Functional integral
representations are derived in both cases, with the alternative between ergodic
measures on real random fields or complex Gaussian random fields.Comment: Late
Supersymmetric Distributions, Hilbert Spaces of Supersymmetric Functions and Quantum Fields
The recently investigated Hilbert-Krein and other positivity structures of
the superspace are considered in the framework of superdistributions. These
tools are applied to problems raised by the rigorous supersymmetric quantum
field theory.Comment: 24 page
From combinations to single-molecule polypharmacology—cromolyn-ibuprofen conjugates for alzheimer’s disease
Despite Alzheimer’s disease (AD) incidence being projected to increase worldwide, the drugs currently on the market can only mitigate symptoms. Considering the failures of the classical paradigm “one target-one drug-one disease” in delivering effective medications for AD, polypharmacology appears to be a most viable therapeutic strategy. Polypharmacology can involve combinations of multiple drugs and/or single chemical entities modulating multiple targets. Taking inspiration from an ongoing clinical trial, this work aims to convert a promising cromolyn–ibuprofen drug combination into single-molecule “codrugs.” Such codrugs should be able to similarly modulate neuroinflammatory and amyloid pathways, while showing peculiar pros and cons. By exploiting a linking strategy, we designed and synthesized a small set of cromolyn–ibuprofen conjugates (4–6). Preliminary plasma stability and neurotoxicity assays allowed us to select diamide 5 and ethanolamide 6 as promising compounds for further studies. We investigated their immunomodulatory profile in immortalized microglia cells, in vitro anti-aggregating activity towards Aβ42-amyloid self-aggregation, and their cellular neuroprotective effect against Aβ42-induced neurotoxicity. The fact that 6 effectively reduced Aβ-induced neuronal death, prompted its investigation into an in vivo model. Notably, 6 was demonstrated to significantly increase the longevity of Aβ42-expressing Drosophila and to improve fly locomotor performance
- …