DUELLING with the MONSTER: the Diary of a Conjecture
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You and AI Conversations About AI Technologies and Their Implications for Society
You and AI Conversations about AI technologies and their implications for society SUPPORTED BY CONVERSATIONS ABOUT AI TECHNOLOGIES AND THEIR IMPLICATIONS FOR SOCIETY DeepMind1 2 CONVERSATIONS ABOUT AI TECHNOLOGIES AND THEIR IMPLICATIONS FOR SOCIETY You and AI Conversations about AI technologies and their implications for society Artificial Intelligence (AI) is the science of making computer systems smart, and an umbrella term for a range of technologies that carry out functions that typically require intelligence in humans. AI technologies already support many everyday products and services, and the power and reach of these technologies are advancing at pace. The Royal Society is working to support an environment of careful stewardship of AI technologies, so that their benefits can be brought into being safely and rapidly, and shared across society. In support of this aim, the Society’s You and AI series brought together leading AI researchers to contribute to a public conversation about advances in AI and their implications for society. CONVERSATIONS ABOUT AI TECHNOLOGIES AND THEIR IMPLICATIONS FOR SOCIETY 3 What AI can, and cannot, do The last decade has seen exciting developments in AI – and AI researchers are tackling some fundamental challenges to develop it further AI research seeks to understand what happens or inputs do not follow a standard intelligence is, and then recreate this through pattern, these systems cannot adapt their computer systems that can automatically rules or adjust their approach. perform tasks that require some level of reasoning or intelligence in humans. In the last decade, new methods that use learning algorithms have helped create In the past, AI research has concentrated computer systems that are more flexible on creating detailed rules for how to carry and adaptive, and Demis Hassabis FRS out a task and then developing computer (co-founder, DeepMind) has been at the systems that could carry out these rules; forefront of many of these developments. -
Derived Categories. Winter 2008/09
Derived categories. Winter 2008/09 Igor V. Dolgachev May 5, 2009 ii Contents 1 Derived categories 1 1.1 Abelian categories .......................... 1 1.2 Derived categories .......................... 9 1.3 Derived functors ........................... 24 1.4 Spectral sequences .......................... 38 1.5 Exercises ............................... 44 2 Derived McKay correspondence 47 2.1 Derived category of coherent sheaves ................ 47 2.2 Fourier-Mukai Transform ...................... 59 2.3 Equivariant derived categories .................... 75 2.4 The Bridgeland-King-Reid Theorem ................ 86 2.5 Exercises ............................... 100 3 Reconstruction Theorems 105 3.1 Bondal-Orlov Theorem ........................ 105 3.2 Spherical objects ........................... 113 3.3 Semi-orthogonal decomposition ................... 121 3.4 Tilting objects ............................ 128 3.5 Exercises ............................... 131 iii iv CONTENTS Lecture 1 Derived categories 1.1 Abelian categories We assume that the reader is familiar with the concepts of categories and func- tors. We will assume that all categories are small, i.e. the class of objects Ob(C) in a category C is a set. A small category can be defined by two sets Mor(C) and Ob(C) together with two maps s, t : Mor(C) → Ob(C) defined by the source and the target of a morphism. There is a section e : Ob(C) → Mor(C) for both maps defined by the identity morphism. We identify Ob(C) with its image under e. The composition of morphisms is a map c : Mor(C) ×s,t Mor(C) → Mor(C). There are obvious properties of the maps (s, t, e, c) expressing the axioms of associativity and the identity of a category. For any A, B ∈ Ob(C) we denote −1 −1 by MorC(A, B) the subset s (A) ∩ t (B) and we denote by idA the element e(A) ∈ MorC(A, A). -
Signed Exceptional Sequences and the Cluster Morphism Category
SIGNED EXCEPTIONAL SEQUENCES AND THE CLUSTER MORPHISM CATEGORY KIYOSHI IGUSA AND GORDANA TODOROV Abstract. We introduce signed exceptional sequences as factorizations of morphisms in the cluster morphism category. The objects of this category are wide subcategories of the module category of a hereditary algebra. A morphism [T ]: A!B is an equivalence class of rigid objects T in the cluster category of A so that B is the right hom-ext perpendicular category of the underlying object jT j 2 A. Factorizations of a morphism [T ] are given by totally orderings of the components of T . This is equivalent to a \signed exceptional sequences." For an algebra of finite representation type, the geometric realization of the cluster morphism category is the Eilenberg-MacLane space with fundamental group equal to the \picture group" introduced by the authors in [IOTW15b]. Contents Introduction 2 1. Definition of cluster morphism category 4 1.1. Wide subcategories 4 1.2. Composition of cluster morphisms 7 1.3. Proof of Proposition 1.8 8 2. Signed exceptional sequences 16 2.1. Definition and basic properties 16 2.2. First main theorem 17 2.3. Permutation of signed exceptional sequences 19 2.4. c -vectors 20 3. Classifying space of the cluster morphism category 22 3.1. Statement of the theorem 23 3.2. HNN extensions and outline of proof 24 3.3. Definitions and proofs 26 3.4. Classifying space of a category and Lemmas 3.18, 3.19 29 3.5. Key lemma 30 3.6. G(S) is an HNN extension of G(S0) 32 4. -
Representations of Semisimple Lie Algebras in Prime Characteristic and the Noncommutative Springer Resolution
Annals of Mathematics 178 (2013), 835{919 http://dx.doi.org/10.4007/annals.2013.178.3.2 Representations of semisimple Lie algebras in prime characteristic and the noncommutative Springer resolution By Roman Bezrukavnikov and Ivan Mirkovic´ To Joseph Bernstein with admiration and gratitude Abstract We prove most of Lusztig's conjectures on the canonical basis in homol- ogy of a Springer fiber. The conjectures predict that this basis controls numerics of representations of the Lie algebra of a semisimple algebraic group over an algebraically closed field of positive characteristic. We check this for almost all characteristics. To this end we construct a noncom- mutative resolution of the nilpotent cone which is derived equivalent to the Springer resolution. On the one hand, this noncommutative resolution is closely related to the positive characteristic derived localization equiva- lences obtained earlier by the present authors and Rumynin. On the other hand, it is compatible with the t-structure arising from an equivalence with the derived category of perverse sheaves on the affine flag variety of the Langlands dual group. This equivalence established by Arkhipov and the first author fits the framework of local geometric Langlands duality. The latter compatibility allows one to apply Frobenius purity theorem to deduce the desired properties of the basis. We expect the noncommutative counterpart of the Springer resolution to be of independent interest from the perspectives of algebraic geometry and geometric Langlands duality. Contents 0. Introduction 837 0.1. Notations and conventions 841 1. t-structures on cotangent bundles of flag varieties: statements and preliminaries 842 R.B. -
2011 Mathematics Newsletter
AUTUMN 2011 NEWSLETTER OF THE DEPARTMENT OF MATHEMATICS AT THE UNIVERSITY OF WASHINGTON Mathematics NEWS 1 DEPARTMENT OF MATHEMATICS NEWS MESSAGE FROM THE CHAIR It has been another exciting year The positive developments reported in this newsletter stand for our department. The work of in contrast to a backdrop of (global) financial and politi- the faculty has been recognized cal uncertainty. In the fourth year of the financial crisis, in a number of ways, includ- the end is not yet in sight. Repeated cuts in state support, ing the AMS Bôcher Prize and coupled with tuition increases, spell a fundamental shift the SIAM Kleinman Prize pre- in the funding of state universities. At the same time, the sented to Gunther Uhlmann, need to re-tool to pursue new career paths in a changing and the NSF CAREER award to economy, the return of soldiers from overseas deployments, Max Lieblich. As you will see on and the coming of age of the baby-boom echo generation page 15, the numbers of majors bring increasing numbers of students to our campus and to in the Mathematics program and the joint ACMS (Applied our department. and Computational Mathematical Sciences) program have Until the situation settles, new resources are generally made continued to rise, as have the numbers of degrees awarded. available to us in the form of temporary allocations instead In addition, these programs attract outstanding students of tenure-track faculty positions, which would require long- who continue to make us proud. For example, Math majors term financial commitments. This policy is understandable. -
From Triangulated Categories to Cluster Algebras
FROM TRIANGULATED CATEGORIES TO CLUSTER ALGEBRAS PHILIPPE CALDERO AND BERNHARD KELLER Abstract. The cluster category is a triangulated category introduced for its combinato- rial similarities with cluster algebras. We prove that a cluster algebra A of finite type can be realized as a Hall algebra, called exceptional Hall algebra, of the cluster category. This realization provides a natural basis for A. We prove new results and formulate conjectures on ‘good basis’ properties, positivity, denominator theorems and toric degenerations. 1. Introduction Cluster algebras were introduced by S. Fomin and A. Zelevinsky [12]. They are subrings of the field Q(u1, . , um) of rational functions in m indeterminates, and defined via a set of generators constructed inductively. These generators are called cluster variables and are grouped into subsets of fixed finite cardinality called clusters. The induction process begins with a pair (x,B), called a seed, where x is an initial cluster and B is a rectangular matrix with integer coefficients. The first aim of the theory was to provide an algebraic framework for the study of total positivity and of Lusztig/Kashiwara’s canonical bases of quantum groups. The first result is the Laurent phenomenon which asserts that the cluster variables, and thus the cluster ±1 ±1 algebra they generate, are contained in the Laurent polynomial ring Z[u1 , . , um ]. Since its foundation, the theory of cluster algebras has witnessed intense activity, both in its own foundations and in its connections with other research areas. One important aim has been to prove, as in [1], [31], that many algebras encountered in the theory of reductive Lie groups have (at least conjecturally) a structure of cluster algebra with an explicit seed. -
Birational Geometry Via Moduli Spaces. 1. Introduction 1.1. Moduli
Birational geometry via moduli spaces. IVAN CHELTSOV, LUDMIL KATZARKOV, VICTOR PRZYJALKOWSKI Abstract. In this paper we connect degenerations of Fano threefolds by projections. Using Mirror Symmetry we transfer these connections to the side of Landau–Ginzburg models. Based on that we suggest a generalization of Kawamata’s categorical approach to birational geometry enhancing it via geometry of moduli spaces of Landau–Ginzburg models. We suggest a conjectural application to Hasset–Kuznetsov–Tschinkel program based on new nonrationality “invariants” we consider — gaps and phantom categories. We make several conjectures for these invariants in the case of surfaces of general type and quadric bundles. 1. Introduction 1.1. Moduli approach to Birational Geometry. In recent years many significant developments have taken place in Minimal Model Program (MMP) (see, for example, [10]) based on the major advances in the study of singularities of pairs. Similarly a categorical approach to MMP was taken by Kawamata. This approach was based on the correspondence Mori fibrations (MF) and semiorthogonal decompositions (SOD). There was no use of the discrepancies and of the effective cone in this approach. In the meantime a new epoch, epoch of wall-crossing has emerged. The current situation with wall-crossing phenomenon, after papers of Seiberg–Witten, Gaiotto–Moore–Neitzke, Vafa–Cecoti and seminal works by Donaldson–Thomas, Joyce–Song, Maulik–Nekrasov– Okounkov–Pandharipande, Douglas, Bridgeland, and Kontsevich–Soibelman, is very sim- ilar to the situation with Higgs Bundles after the works of Higgs and Hitchin — it is clear that general “Hodge type” of theory exists and needs to be developed. This lead to strong mathematical applications — uniformization, Langlands program to mention a few. -
Agnieszka Bodzenta
June 12, 2019 HOMOLOGICAL METHODS IN GEOMETRY AND TOPOLOGY AGNIESZKA BODZENTA Contents 1. Categories, functors, natural transformations 2 1.1. Direct product, coproduct, fiber and cofiber product 4 1.2. Adjoint functors 5 1.3. Limits and colimits 5 1.4. Localisation in categories 5 2. Abelian categories 8 2.1. Additive and abelian categories 8 2.2. The category of modules over a quiver 9 2.3. Cohomology of a complex 9 2.4. Left and right exact functors 10 2.5. The category of sheaves 10 2.6. The long exact sequence of Ext-groups 11 2.7. Exact categories 13 2.8. Serre subcategory and quotient 14 3. Triangulated categories 16 3.1. Stable category of an exact category with enough injectives 16 3.2. Triangulated categories 22 3.3. Localization of triangulated categories 25 3.4. Derived category as a quotient by acyclic complexes 28 4. t-structures 30 4.1. The motivating example 30 4.2. Definition and first properties 34 4.3. Semi-orthogonal decompositions and recollements 40 4.4. Gluing of t-structures 42 4.5. Intermediate extension 43 5. Perverse sheaves 44 5.1. Derived functors 44 5.2. The six functors formalism 46 5.3. Recollement for a closed subset 50 1 2 AGNIESZKA BODZENTA 5.4. Perverse sheaves 52 5.5. Gluing of perverse sheaves 56 5.6. Perverse sheaves on hyperplane arrangements 59 6. Derived categories of coherent sheaves 60 6.1. Crash course on spectral sequences 60 6.2. Preliminaries 61 6.3. Hom and Hom 64 6.4. -
(Ben) the Convolution Is an Important Way of Combining Two Functions, Letting Us “Smooth Out” Functions That Are Very Rough
CLASS DESCRIPTIONS|MATHCAMP 2019 Classes A Convoluted Process. (Ben) The convolution is an important way of combining two functions, letting us \smooth out" functions that are very rough. In this course, we'll investigate the convolution and see its connection to the Fourier transform. At the end of the course, we'll explain the Bessel integrals: a sequence of trigono- π metric integrals where the first 7 are all equal to 2 . and then all the rest are not. Why does this pattern start? Why does it stop? One explanation for this phenomenon is based on the convolution. Prerequisites: Know how to take integrals (including improper integrals), some familiarity with limits Algorithms in Number Theory. (Misha) We will discuss which number-theoretic problems can be solved efficiently, and what “efficiently" even means in this case. We will learn how to tell if a 100-digit number is prime, and maybe also how we can tell that 282 589 933 − 1 is prime. We will talk about what's easy and what's hard about solving (linear, quadratic, higher-order) equations modulo n. We may also see a few applications of these ideas to cryptography. Prerequisites: Number theory: you should be comfortable with modular arithmetic (including inverses and exponents) and no worse than mildly uncomfortable with quadratic reciprocity. All About Quaternions. (Assaf + J-Lo) On October 16, 1843, William Rowan Hamilton was crossing the Brougham Bridge in Dublin, when he had a flash of insight and carved the following into the stone: i2 = j2 = k2 = ijk = −1: This two-week course will take you through a guided series of exercises that explore the many impli- cations of this invention, and how they can be used to describe everything from the rotations of 3-D space to which integers can be expressed as a sum of four squares. -
Career Pathway Tracker 35 Years of Supporting Early Career Research Fellows Contents
Career pathway tracker 35 years of supporting early career research fellows Contents President’s foreword 4 Introduction 6 Scientific achievements 8 Career achievements 14 Leadership 20 Commercialisation 24 Public engagement 28 Policy contribution 32 How have the fellowships supported our alumni? 36 Who have we supported? 40 Where are they now? 44 Research Fellowship to Fellow 48 Cover image: Graphene © Vertigo3d CAREER PATHWAY TRACKER 3 President’s foreword The Royal Society exists to encourage the development and use of Very strong themes emerge from the survey About this report science for the benefit of humanity. One of the main ways we do that about why alumni felt they benefited. The freedom they had to pursue the research they This report is based on the first is by investing in outstanding scientists, people who are pushing the wanted to do because of the independence Career Pathway Tracker of the alumni of University Research Fellowships boundaries of our understanding of ourselves and the world around the schemes afford is foremost in the minds of respondents. The stability of funding and and Dorothy Hodgkin Fellowships. This us and applying that understanding to improve lives. flexibility are also highly valued. study was commissioned by the Royal Society in 2017 and delivered by the Above Thirty-five years ago, the Royal Society The vast majority of alumni who responded The Royal Society has long believed in the Careers Research & Advisory Centre Venki Ramakrishnan, (CRAC), supported by the Institute for President of the introduced our University Research Fellowships to the survey – 95% of University Research importance of identifying and nurturing the Royal Society. -
CLASS DESCRIPTIONS—WEEK 5, MATHCAMP 2019 Contents 9:10
CLASS DESCRIPTIONS|WEEK 5, MATHCAMP 2019 Contents 9:10 Classes 1 10:10 Classes 3 11:10 Classes 6 1:10 Classes 9 2:10 Classes 11 Colloquia 13 Visitor Bios 13 9:10 Classes Electrifying Random Trees. (Will, Tuesday{Wednesday) Consider a graph, and a particular edge in this graph. A natural question to ask is: how important is this edge in connecting the graph together? Here are two ways we might quantify this importance: (1) The spanning trees of the graph give all the ways of minimally connecting the vertices using a subset of the edges. So look at all the spanning trees, and figure out how many of them contain our edge. Put another way, what is the probability that a random spanning tree contains the edge? (2) Build your graph out of 1-ohm resistors. Hook up a 1-volt battery to the ends of your edge, and then measure how many amps of current are passing through that edge (as opposed to going through other paths in the graph). These two numbers are actually the same! In this class, we'll see why. On the way, we'll see how one might generate a random spanning tree in the first place. Chilis: Homework: Recommended. Prerequisites: Familiarity with the language of graphs (i.e., what a tree is; what the degree of a vertex is). Farey Tales. (J-Lo, Tuesday{Friday) The goal of this course is to understand this picture: 1 MC2019 ◦ W5 ◦ Classes 2 Along the way we will encounter Farey series, the Euclidean algorithm, and a geometric interpre- tation of continued fractions. -
Mathematical Tripos Part III Lecture Courses in 2012-2013
Mathematical Tripos Part III Lecture Courses in 2012-2013 Department of Pure Mathematics & Mathematical Statistics Department of Applied Mathematics & Theoretical Physics Notes and Disclaimers. • Students may take any combination of lectures that is allowed by the timetable. The examination timetable corresponds to the lecture timetable and it is therefore not possible to take two courses for examination that are lectured in the same timetable slot. There is no requirement that students study only courses offered by one Department. • The code in parentheses after each course name indicates the term of the course (M: Michaelmas; L: Lent; E: Easter), and the number of lectures in the course. Unless indicated otherwise, a 16 lecture course is equivalent to 2 credit units, while a 24 lecture course is equivalent to 3 credit units. Please note that certain courses are non-examinable. Some of these courses may be the basis for Part III essays. • At the start of some sections there is a paragraph indicating the desirable previous knowledge for courses in that section. On one hand, such paragraphs are not exhaustive, whilst on the other, not all courses require all the pre-requisite material indicated. However you are strongly recommended to read up on the material with which you are unfamiliar if you intend to take a significant number of courses from a particular section. • The courses described in this document apply only for the academic year 2012-13. Details for subsequent years are often broadly similar, but not necessarily identical. The courses evolve from year to year. • Please note that while an attempt has been made to ensure that the outlines in this booklet are an accurate indication of the content of courses, the outlines do not constitute definitive syllabuses.