7,250 research outputs found

    Associated neutralino-neutralino-photon production at NLC

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    We study the potential of an e+ee^+e^- 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

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    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

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    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

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    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

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    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

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    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
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