7,653 research outputs found
Associated neutralino-neutralino-photon production at NLC
We study the potential of an linear collider to search for
neutralino-neutralino-photon production. Our analysis shows that this signal is
not viable under realistic expectations for electron beam polarization due to
large Standard Model backgrounds. Such a search would be possible only if beam
polarizations of near 100% could be achieved.Comment: 3 pages, 6 figures, uses RevTeX4. Contribution to Snowmass 200
Self-protection and insurance with interdependencies
We study optimal investment in self-protection of insured individuals when they face interdependencies in the form of potential contamination from others. If individuals cannot coordinate their actions, then the positive externality of investing in self-protection implies that, in equilibrium, individuals underinvest in self-protection. Limiting insurance coverage through deductibles or selling “at-fault” insurance can partially internalize this externality and thereby improve individual and social welfare. JEL Classification: C72, D62, D8
Local tomography and the Jordan structure of quantum theory
Using a result of H. Hanche-Olsen, we show that (subject to fairly natural
constraints on what constitutes a system, and on what constitutes a composite
system), orthodox finite-dimensional complex quantum mechanics with
superselection rules is the only non-signaling probabilistic theory in which
(i) individual systems are Jordan algebras (equivalently, their cones of
unnormalized states are homogeneous and self-dual), (ii) composites are locally
tomographic (meaning that states are determined by the joint probabilities they
assign to measurement outcomes on the component systems) and (iii) at least one
system has the structure of a qubit. Using this result, we also characterize
finite dimensional quantum theory among probabilistic theories having the
structure of a dagger-monoidal category
Self-Protection and Insurance with Interdependencies
We study optimal investment in self-protection of insured individuals when they face interdependencies in the form of potential contamination from others. If individuals cannot coordinate their actions, then the positive externality of investing in self-protection implies that, in equilibrium, individuals underinvest in self-protection. Limiting insurance coverage through deductibles can partially internalize this externality and thereby improve individual and social welfare.
Relic density of neutralinos in minimal supergravity
We evaluate the relic density of neutralinos in the minimal supergravity
(mSUGRA) model. All 2->2 neutralino annihilation diagrams, as well as all
initial states involving sleptons, charginos, neutralinos and third generation
squarks are included. Relativistic thermal averaging of the velocity times
cross sections is performed. We find that co-annihilation effects are only
important on the edges of the model parameter space, where some amount of
fine-tuning is necessary to obtain a reasonable relic density. Alternatively,
at high tan(beta), annihilation through the broad Higgs resonances gives rise
to an acceptable neutralino relic density over broad regions of parameter space
where little or no fine-tuning is needed.Comment: LaTeX, 10 pages. Talk given by Alexander Belyaev at SUSY'02, "The
10th International Conference on Supersymmetry and Unification of Fundamental
Interactions", DESY, Hamburg, Germany, 17-23 June 200
Symmetry, Compact Closure and Dagger Compactness for Categories of Convex Operational Models
In the categorical approach to the foundations of quantum theory, one begins
with a symmetric monoidal category, the objects of which represent physical
systems, and the morphisms of which represent physical processes. Usually, this
category is taken to be at least compact closed, and more often, dagger
compact, enforcing a certain self-duality, whereby preparation processes
(roughly, states) are inter-convertible with processes of registration
(roughly, measurement outcomes). This is in contrast to the more concrete
"operational" approach, in which the states and measurement outcomes associated
with a physical system are represented in terms of what we here call a "convex
operational model": a certain dual pair of ordered linear spaces -- generally,
{\em not} isomorphic to one another. On the other hand, state spaces for which
there is such an isomorphism, which we term {\em weakly self-dual}, play an
important role in reconstructions of various quantum-information theoretic
protocols, including teleportation and ensemble steering. In this paper, we
characterize compact closure of symmetric monoidal categories of convex
operational models in two ways: as a statement about the existence of
teleportation protocols, and as the principle that every process allowed by
that theory can be realized as an instance of a remote evaluation protocol ---
hence, as a form of classical probabilistic conditioning. In a large class of
cases, which includes both the classical and quantum cases, the relevant
compact closed categories are degenerate, in the weak sense that every object
is its own dual. We characterize the dagger-compactness of such a category
(with respect to the natural adjoint) in terms of the existence, for each
system, of a {\em symmetric} bipartite state, the associated conditioning map
of which is an isomorphism
Some Nearly Quantum Theories
We consider possible non-signaling composites of probabilistic models based
on euclidean Jordan algebras. Subject to some reasonable constraints, we show
that no such composite exists having the exceptional Jordan algebra as a direct
summand. We then construct several dagger compact categories of such
Jordan-algebraic models. One of these neatly unifies real, complex and
quaternionic mixed-state quantum mechanics, with the exception of the
quaternionic "bit". Another is similar, except in that (i) it excludes the
quaternionic bit, and (ii) the composite of two complex quantum systems comes
with an extra classical bit. In both of these categories, states are morphisms
from systems to the tensor unit, which helps give the categorical structure a
clear operational interpretation. A no-go result shows that the first of these
categories, at least, cannot be extended to include spin factors other than the
(real, complex, and quaternionic) quantum bits, while preserving the
representation of states as morphisms. The same is true for attempts to extend
the second category to even-dimensional spin-factors. Interesting phenomena
exhibited by some composites in these categories include failure of local
tomography, supermultiplicativity of the maximal number of mutually
distinguishable states, and mixed states whose marginals are pure.Comment: In Proceedings QPL 2015, arXiv:1511.0118
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