24,697 research outputs found
The Minimal SUSY Model: From the Unification Scale to the LHC
This paper introduces a random statistical scan over the high-energy initial
parameter space of the minimal SUSY model--denoted as the MSSM.
Each initial set of points is renormalization group evolved to the electroweak
scale--being subjected, sequentially, to the requirement of radiative and
electroweak symmetry breaking, the present experimental lower bounds on the
vector boson and sparticle masses, as well as the lightest neutral Higgs
mass of 125 GeV. The subspace of initial parameters that satisfies all
such constraints is presented, shown to be robust and to contain a wide range
of different configurations of soft supersymmetry breaking masses. The
low-energy predictions of each such "valid" point - such as the sparticle mass
spectrum and, in particular, the LSP - are computed and then statistically
analyzed over the full subspace of valid points. Finally, the amount of
fine-tuning required is quantified and compared to the MSSM computed using an
identical random scan. The MSSM is shown to generically require less
fine-tuning.Comment: 65 pages, 18 figure
Monetary Union and Central Bank Independence
We study the consequences of forming a monetary union among a group of countries where the central banks lack independence and are pressured frequently to accommodate government objectives. This is a common situation in the developing countries. As it is common in the literature, we show that forming a monetary union yields net benefits if output shocks are similar across the member countries and if one or more countries in the union can serve as anchors. Our framework highlights an additional gain from monetary union. We show that the opportunistic objectives of one country's policymakers are kept in check at the union level by other members with disparate objectives. Hence, monetary union can improve the monetary policy for its members if the pressures on the individual central banks are dissimilar. We calibrate the model to evaluate the proposed monetary union in the East African Community. Working Paper 06-5
A Bi-Directional Refinement Algorithm for the Calculus of (Co)Inductive Constructions
The paper describes the refinement algorithm for the Calculus of
(Co)Inductive Constructions (CIC) implemented in the interactive theorem prover
Matita. The refinement algorithm is in charge of giving a meaning to the terms,
types and proof terms directly written by the user or generated by using
tactics, decision procedures or general automation. The terms are written in an
"external syntax" meant to be user friendly that allows omission of
information, untyped binders and a certain liberal use of user defined
sub-typing. The refiner modifies the terms to obtain related well typed terms
in the internal syntax understood by the kernel of the ITP. In particular, it
acts as a type inference algorithm when all the binders are untyped. The
proposed algorithm is bi-directional: given a term in external syntax and a
type expected for the term, it propagates as much typing information as
possible towards the leaves of the term. Traditional mono-directional
algorithms, instead, proceed in a bottom-up way by inferring the type of a
sub-term and comparing (unifying) it with the type expected by its context only
at the end. We propose some novel bi-directional rules for CIC that are
particularly effective. Among the benefits of bi-directionality we have better
error message reporting and better inference of dependent types. Moreover,
thanks to bi-directionality, the coercion system for sub-typing is more
effective and type inference generates simpler unification problems that are
more likely to be solved by the inherently incomplete higher order unification
algorithms implemented. Finally we introduce in the external syntax the notion
of vector of placeholders that enables to omit at once an arbitrary number of
arguments. Vectors of placeholders allow a trivial implementation of implicit
arguments and greatly simplify the implementation of primitive and simple
tactics
Compiling and securing cryptographic protocols
Protocol narrations are widely used in security as semi-formal notations to
specify conversations between roles. We define a translation from a protocol
narration to the sequences of operations to be performed by each role. Unlike
previous works, we reduce this compilation process to well-known decision
problems in formal protocol analysis. This allows one to define a natural
notion of prudent translation and to reuse many known results from the
literature in order to cover more crypto-primitives. In particular this work is
the first one to show how to compile protocols parameterised by the properties
of the available operations.Comment: A short version was submitted to IP
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