40,059 research outputs found
Choosing Your Nonmonotonic Logic: A Shopper’s Guide
The paper presents an exhaustive menu of nonmonotonic logics. The options are individuated in terms of the principles they reject. I locate, e.g., cumulative logics and relevance logics on this menu. I highlight some frequently neglected options, and I argue that these neglected options are particularly attractive for inferentialists
GAMMA: A Mathematica package for performing gamma-matrix algebra and Fierz transformations in arbitrary dimensions
We have developed a Mathematica package capable of performing gamma-matrix
algebra in arbitrary (integer) dimensions. As an application we can compute
Fierz transformations.Comment: 12 pages, LaTeX, v2: some clarifications added, updated package
availabl
Extended supersymmetry of semichiral sigma model in 4D
Briefly: Using a novel superspace formulation of semichiral sigma
models with target space, we investigate if an extended supersymmetry in
terms of semichirals is compatible with having a target space with
torsion.
In more detail: Semichiral sigma models have supersymmetry and
Generalized K\"ahler target space geometry by construction. They can also
support supersymmetry and Generalized Hyperk\"ahler geometry, but when
the target space is four dimensional indications are that the geometry is
restricted to Hyperk\"ahler. To investigate this further, we reduce the model
to superspace and construct the extra (on-shell) supersymmetries there.
We then find the conditions for a lift to super space and semichiral
fields to exist. Those conditions are shown to hold for Hyperk\"ahler
geometries. The WZW model, which has supersymmetry
and a semichiral description, is also investigated. The additional
supersymmetries are found in superspace but shown {\em not} to be
liftable to a semichiral formulation.Comment: 23 pages. Resubmitted after compilation problem
Expressing Validity: Towards a Self-Sufficient Inferentialism
For semantic inferentialists, the basic semantic concept is validity. An inferentialist theory of meaning should offer an account of the meaning of "valid." If one tries to add a validity predicate to one's object language, however, one runs into problems like the v-Curry paradox. In previous work, I presented a validity predicate for a non-transitive logic that can adequately capture its own meta-inferences. Unfortunately, in that system, one cannot show of any inference that it is invalid. Here I extend the system so that it can capture invalidities
A stability criterion for systems with neutrally stable modes and deadzone nonlinearities
Stability analysis is considered for feedback interconnections of deadzone nonlinearities with linear systems that has a neutrally stable mode. Such systems do not have a unique equilibrium point and the standard techniques from passivity and Lyapunov theory cannot be applied. A stability criterion that generalizes the Popov criterion for this class of systems is derived in this report and several examples will prove its applicability
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