295 research outputs found
Graph classes and forbidden patterns on three vertices
This paper deals with graph classes characterization and recognition. A
popular way to characterize a graph class is to list a minimal set of forbidden
induced subgraphs. Unfortunately this strategy usually does not lead to an
efficient recognition algorithm. On the other hand, many graph classes can be
efficiently recognized by techniques based on some interesting orderings of the
nodes, such as the ones given by traversals.
We study specifically graph classes that have an ordering avoiding some
ordered structures. More precisely, we consider what we call patterns on three
nodes, and the recognition complexity of the associated classes. In this
domain, there are two key previous works. Damashke started the study of the
classes defined by forbidden patterns, a set that contains interval, chordal
and bipartite graphs among others. On the algorithmic side, Hell, Mohar and
Rafiey proved that any class defined by a set of forbidden patterns can be
recognized in polynomial time. We improve on these two works, by characterizing
systematically all the classes defined sets of forbidden patterns (on three
nodes), and proving that among the 23 different classes (up to complementation)
that we find, 21 can actually be recognized in linear time.
Beyond this result, we consider that this type of characterization is very
useful, leads to a rich structure of classes, and generates a lot of open
questions worth investigating.Comment: Third version version. 38 page
Computability in constructive type theory
We give a formalised and machine-checked account of computability theory in the Calculus of Inductive Constructions (CIC), the constructive type theory underlying the Coq proof assistant. We first develop synthetic computability theory, pioneered by Richman, Bridges, and Bauer, where one treats all functions as computable, eliminating the need for a model of computation. We assume a novel parametric axiom for synthetic computability and give proofs of results like Riceâs theorem, the Myhill isomorphism theorem, and the existence of Postâs simple and hypersimple predicates relying on no other axioms such as Markovâs principle or choice axioms. As a second step, we introduce models of computation. We give a concise overview of definitions of various standard models and contribute machine-checked simulation proofs, posing a non-trivial engineering effort. We identify a notion of synthetic undecidability relative to a fixed halting problem, allowing axiom-free machine-checked proofs of undecidability. We contribute such undecidability proofs for the historical foundational problems of computability theory which require the identification of invariants left out in the literature and now form the basis of the Coq Library of Undecidability Proofs. We then identify the weak call-by-value λ-calculus L as sweet spot for programming in a model of computation. We introduce a certifying extraction framework and analyse an axiom stating that every function of type â â â is L-computable.Wir behandeln eine formalisierte und maschinengeprĂŒfte Betrachtung von Berechenbarkeitstheorie im Calculus of Inductive Constructions (CIC), der konstruktiven Typtheorie die dem Beweisassistenten Coq zugrunde liegt. Wir entwickeln erst synthetische Berechenbarkeitstheorie, vorbereitet durch die Arbeit von Richman, Bridges und Bauer, wobei alle Funktionen als berechenbar behandelt werden, ohne Notwendigkeit eines Berechnungsmodells. Wir nehmen ein neues, parametrisches Axiom fĂŒr synthetische Berechenbarkeit an und beweisen Resultate wie das Theorem von Rice, das Isomorphismus Theorem von Myhill und die Existenz von Postâs simplen und hypersimplen PrĂ€dikaten ohne Annahme von anderen Axiomen wie Markovâs Prinzip oder Auswahlaxiomen. Als zweiten Schritt fĂŒhren wir Berechnungsmodelle ein. Wir geben einen kompakten Ăberblick ĂŒber die Definition von verschiedenen Berechnungsmodellen und erklĂ€ren maschinengeprĂŒfte Simulationsbeweise zwischen diesen Modellen, welche einen hohen Konstruktionsaufwand beinhalten. Wir identifizieren einen Begriff von synthetischer Unentscheidbarkeit relativ zu einem fixierten Halteproblem welcher axiomenfreie maschinengeprĂŒfte Unentscheidbarkeitsbeweise erlaubt. Wir erklĂ€ren solche Beweise fĂŒr die historisch grundlegenden Probleme der Berechenbarkeitstheorie, die das Identifizieren von Invarianten die normalerweise in der Literatur ausgelassen werden benötigen und nun die Basis der Coq Library of Undecidability Proofs bilden. Wir identifizieren dann den call-by-value λ-KalkĂŒl L als sweet spot fĂŒr die Programmierung in einem Berechnungsmodell. Wir fĂŒhren ein zertifizierendes Extraktionsframework ein und analysieren ein Axiom welches postuliert dass jede Funktion vom Typ NâN L-berechenbar ist
Simple Stochastic Games with Almost-Sure Energy-Parity Objectives are in NP and coNP
We study stochastic games with energy-parity objectives, which combine
quantitative rewards with a qualitative -regular condition: The
maximizer aims to avoid running out of energy while simultaneously satisfying a
parity condition. We show that the corresponding almost-sure problem, i.e.,
checking whether there exists a maximizer strategy that achieves the
energy-parity objective with probability when starting at a given energy
level , is decidable and in . The same holds for checking if
such a exists and if a given is minimal
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Complexity Theory
Computational Complexity Theory is the mathematical study of the intrinsic power and limitations of computational resources like time, space, or randomness. The current workshop focused on recent developments in various sub-areas including arithmetic complexity, Boolean complexity, communication complexity, cryptography, probabilistic proof systems, pseudorandomness, and quantum computation. Many of the developements are related to diverse mathematical ïŹelds such as algebraic geometry, combinatorial number theory, probability theory, quantum mechanics, representation theory, and the theory of error-correcting codes
Liberty, Property and Rationality : Concept of Freedom in Murray Rothbard's Anarcho-capitalism
Murray Rothbard (1926â1995) on yksi keskeisimmistĂ€ modernin libertarismin taustalla olevista ajattelijoista. Rothbard pitÀÀ yksilöllistĂ€ vapautta keskeisimpĂ€nĂ€ periaatteenaan, ja yhdistÀÀ filosofiassaan klassisen liberalismin perinnettĂ€ itĂ€valtalaiseen taloustieteeseen, teleologiseen luonnonoikeusajatteluun sekĂ€ individualistiseen anarkismiin. HĂ€nen tavoitteenaan on kehittÀÀ puhtaaseen jĂ€rkeen pohjautuva oikeusoppi, jonka pohjalta voidaan perustaa vapaiden markkinoiden ihanneyhteiskunta. Valtiota ei tĂ€ten Rothbardin ihanneyhteiskunnassa ole, vaan vastuu yksilöllisten luonnonoikeuksien toteutumisesta on kokonaan yksilöllĂ€ itsellÀÀn.
Tutkin työssÀni vapauden kÀsitettÀ Rothbardin anarko-kapitalistisessa filosofiassa. SelvitÀn ja analysoin Rothbardin ajattelun keskeisimpiÀ elementtejÀ niiden filosofisissa, ideologisissa, poliittisissa ja henkilöhistoriallisissa konteksteissaan. KÀytÀn nÀiden elementtien arviointiin sekÀ historiatieteen ettÀ filosofian lÀhestymistapaa. TÀssÀ mielessÀ työni edustaa sekÀ aate- ettÀ filosofian historiaa. HyödynnÀn tutkimuksessani Isaiah Berlinin negatiivisen ja positiivisen vapauden teoriaa (1958). Nojaudun vapauden kÀsitteen analysoinnissa klassisen liberalismin traditioon, jota työssÀni keskeisimmin edustaa Berlinin lisÀksi John Stuart Millin filosofia (1859). TÀhÀn viitekehykseen tukeutuen esitÀn, ettei Rothbardin vapauden teoria edusta liberalistista ajattelua, vaan on selkeÀsti tÀmÀn tradition ulkopuolella niin metaeettisen teoriansa, yhteiskunnallisten arvojensa kuin perimmÀisen vapauskÀsityksensÀkin puolesta.
Vapauden kĂ€sitteellĂ€ on Rothbardin filosofiassa kaksi toisistaan erottuvaa merkitystĂ€. Rothbard viittaa vapauden termillĂ€ useimmiten praxeologisen taloustieteen logiikkaan perustuvaan, vĂ€linearvolliseen âmoraalitieteeseenâ ja tĂ€mĂ€n pohjalta johdettuun vapauden objektiiviseen mÀÀritelmÀÀn luonnollisena tosiasiana. Toisaalta hĂ€n viittaa termillĂ€ myös normatiiviseen, itseisarvolliseen poliittiseen ihanteeseen. Tutkimustavoitteenani on selvittÀÀ, miten nĂ€mĂ€ kaksi merkitystĂ€ lopulta yhdistyvĂ€t Rothbardin ajattelussa toisiinsa. Teen tĂ€ten ymmĂ€rrettĂ€vĂ€ksi, mitĂ€ vapaus lopulta tarkoittaa Rothbardin filosofiassa. PrimÀÀrilĂ€hteinĂ€ni on Rothbardin kirjallinen tuotanto vuosilta 1960â1982. HĂ€nen poliittisen filosofiansa kannalta keskeisimmĂ€t teokset ovat âEthics of Libertyâ (1982) sekĂ€ âFor a New Libertyâ (1973). Tukeudun tutkimuksessani myös Rothbardista tehtyihin elĂ€mĂ€kerrallisiin selvityksiin, joita ovat kirjoittaneet Rothbardin lĂ€hipiiriin ja kannattajakuntaan kuuluneet akateemikot.
Tutkimustulosteni pohjalta vÀitÀn, ettei anarko-kapitalismi ole luonnollisiin tosiasioihin ja puhtaaseen jÀrkeen pohjautuva eettinen systeemi, vaan pohjimmiltaan uskonnollisen moraalin pÀÀlle rakentuva vapaiden markkinoiden ideologia, jossa vapauden vÀlinearvollinen mÀÀritelmÀ yhdistyy vapauden poliittiseen ihanteeseen lopulta vain sen olettamuksen kautta, ettÀ olemme epÀvapaita valtion takia
Metaethical Minimalism: A Demarcation, Defense, and Development
The aim of this work is to demarcate, develop, and defend the commitments and
consequences of metaethical minimalism. Very roughly, this is the position that a
commitment to objective moral truths does not require any accompanying ontological
commitments. While there are few, if any, who call themselves âmetaethical minimalistsâ, I
endeavor to uncover existing articulations of metaethical minimalism which have been
presented under different names, attempting to identify the common ground between
them. As I interpret the position, all metaethical minimalists are committed to the same
positive pair of claims (what I call the Objectivity Thesis): âa) Moral truths are strongly
mind-independent; b) there are moral truths.â Taken by itself, however, this pair of claims
is not sufficient for differentiating their view from the moral realistâs. Consequently, the
minimalist must also articulate that which they are denying about the non-minimalist
approach, or what I call the ânegative ontological thesisâ. I offer my own version of this
negative thesis and argue for its dialectical advantages.
In Chapters 3 and 4, I focus my attention on attacks on the viability of metaethical
minimalism in the form of two âchallengesâ that aim to problematize a commitment to
objective moral truths absent any accompanying ontological commitment. The
big-picture takeaway from these chapters is that minimalism can defend itself by playing to
the dialectical advantage I find for it in Chapter 2 as well as by being creative about
minimalist constructions/reworkings of plausible principles/lines of reasoning that seem
to contradict it.
The temptation to embrace quietism is strong among minimalists, but in Chapters
5, 6, and 7 I aim to show that there is a positive alternative available for the minimalist
interested in developing a full picture of their position. Chapter 5 is aimed at providing an
adequate understanding of the distinction between the objects of purely normative
thoughts and objects of thoughts about reality. Building on this are Chapters 6 and 7,
which argue in favor of an account of the relationship between emotion and evaluative
knowledge that is consistent with metaethical minimalism
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