2,284 research outputs found
On-Shell Methods in Perturbative QCD
We review on-shell methods for computing multi-parton scattering amplitudes
in perturbative QCD, utilizing their unitarity and factorization properties. We
focus on aspects which are useful for the construction of one-loop amplitudes
needed for phenomenological studies at the Large Hadron Collider.Comment: 49 pages, 15 figures. v2: minor typos correcte
Arrow's Theorem, countably many agents, and more visible invisible dictators
For infinite societies, Fishburn (1970), Kirman and Sondermann (1972), and Armstrong (1980) gave a nonconstructive proof of the existence of a social welfare function satisfying Arrowfs conditions (Unanimity, Independence, and Nondictatorship). This paper improves on their results by (i) giving a concrete example of such a function, and (ii) showing how to compute, from a description of a profile on a pair of alternatives, which alternative is socially preferred under the function. The introduction of a certain goracleh resolves Miharafs impossibility result (1997) about computability of social welfare functions.Arrow impossibility theorem, Turing computability, recursion theory, oracle algorithms, free ultrafilters
Time Window Temporal Logic
This paper introduces time window temporal logic (TWTL), a rich expressivity
language for describing various time bounded specifications. In particular, the
syntax and semantics of TWTL enable the compact representation of serial tasks,
which are typically seen in robotics and control applications. This paper also
discusses the relaxation of TWTL formulae with respect to deadlines of tasks.
Efficient automata-based frameworks to solve synthesis, verification and
learning problems are also presented. The key ingredient to the presented
solution is an algorithm to translate a TWTL formula to an annotated finite
state automaton that encodes all possible temporal relaxations of the
specification. Case studies illustrating the expressivity of the logic and the
proposed algorithms are included
Safe Recursion on Notation into a Light Logic by Levels
We embed Safe Recursion on Notation (SRN) into Light Affine Logic by Levels
(LALL), derived from the logic L4. LALL is an intuitionistic deductive system,
with a polynomial time cut elimination strategy.
The embedding allows to represent every term t of SRN as a family of proof
nets |t|^l in LALL. Every proof net |t|^l in the family simulates t on
arguments whose bit length is bounded by the integer l. The embedding is based
on two crucial features. One is the recursive type in LALL that encodes Scott
binary numerals, i.e. Scott words, as proof nets. Scott words represent the
arguments of t in place of the more standard Church binary numerals. Also, the
embedding exploits the "fuzzy" borders of paragraph boxes that LALL inherits
from L4 to "freely" duplicate the arguments, especially the safe ones, of t.
Finally, the type of |t|^l depends on the number of composition and recursion
schemes used to define t, namely the structural complexity of t. Moreover, the
size of |t|^l is a polynomial in l, whose degree depends on the structural
complexity of t.
So, this work makes closer both the predicative recursive theoretic
principles SRN relies on, and the proof theoretic one, called /stratification/,
at the base of Light Linear Logic
Time window temporal logic
This paper introduces time window temporal logic (TWTL), a rich expressive language for describing various time bounded specifications. In particular, the syntax and semantics of TWTL enable the compact representation of serial tasks, which are prevalent in various applications including robotics, sensor systems, and manufacturing systems. This paper also discusses the relaxation of TWTL formulae with respect to the deadlines of the tasks. Efficient automata-based frameworks are presented to solve synthesis, verification and learning problems. The key ingredient to the presented solution is an algorithm to translate a TWTL formula to an annotated finite state automaton that encodes all possible temporal relaxations of the given formula. Some case studies are presented to illustrate the expressivity of the logic and the proposed algorithms
Approximating High-Dimensional Dynamic Models: Sieve Value Function Iteration
Many dynamic problems in economics are characterized by large state spaces which make both computing and estimating the model infeasible. We introduce a method for approximating the value function of high-dimensional dynamic models based on sieves and establish results for the: (a) consistency, (b) rates of convergence, and (c) bounds on the error of approximation. We embed this method for approximating the solution to the dynamic problem within an estimation routine and prove that it provides consistent estimates of the model's parameters. We provide Monte Carlo evidence that our method can successfully be used to approximate models that would otherwise be infeasible to compute, suggesting that these techniques may substantially broaden the class of models that can be solved and estimated.
Complexity Hierarchies Beyond Elementary
We introduce a hierarchy of fast-growing complexity classes and show its
suitability for completeness statements of many non elementary problems. This
hierarchy allows the classification of many decision problems with a
non-elementary complexity, which occur naturally in logic, combinatorics,
formal languages, verification, etc., with complexities ranging from simple
towers of exponentials to Ackermannian and beyond.Comment: Version 3 is the published version in TOCT 8(1:3), 2016. I will keep
updating the catalogue of problems from Section 6 in future revision
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