Schemes 10: Morphisms of affine schemes
This lecture is part of an online algebraic geometry course on schemes, based on chapter II of "Algebraic geometry" by Hartshorne. We try to define morphisms of schemes. The obvious definition as morphisms of ringed spaces fails as we show in an example. Instead we have to use the more su
From playlist Algebraic geometry II: Schemes
Schemes 16: Morphisms of finite type
This lecture is part of an online algebraic geometry course on schemes, based on chapter II of "Algebraic geometry" by Hartshorne. We introduce three properties of morphisms: quasicompact, finite type, and locally of finite type, and give a few examples.
From playlist Algebraic geometry II: Schemes
Schemes 41: Morphisms to projective space
This lecture is part of an online course on algebraic geometry based on chapter II of "algebraic geometry" by Hartshorne. We discuss morphisms of a scheme to projective space, showing that they correspond to a line bundle with a set of sections generating it.
From playlist Algebraic geometry II: Schemes
algebraic geometry 25 Morphisms of varieties
This lecture is part of an online algebraic geometry course, based on chapter I of "Algebraic geometry" by Hartshorne. It covers the definition of a morphism of varieties and compares algebraic varieties with other types of locally ringed spaces.
From playlist Algebraic geometry I: Varieties
This lecture is part of an online algebraic geometry course on schemes, based on chapter II of "Algebraic geometry" by Hartshorne.. We define proper morphisms in topology and geometry, and show that finite morphisms are proper.
From playlist Algebraic geometry II: Schemes
Schemes 5: Definition of a scheme
This lecture is part of an online algebraic geometry course on schemes, based on chapter II of "Algebraic geometry" by Hartshorne. We give some historical background, then give the definition of a scheme and some simple examples, and finish by explaining the origin of the word "spectrum".
From playlist Algebraic geometry II: Schemes
Schemes 13: The functor of points
This lecture is part of an online algebraic geometry course on schemes, based on chapter II of "Algebraic geometry" by Hartshorne. We discuss two themes in Grothendieck's work on schemes. The first one is that one should focus on morphisms of schemes rather than schemes. The second is that
From playlist Algebraic geometry II: Schemes
Schemes 17: Finite, quasifinite
This lecture is part of an online algebraic geometry course on schemes, based on chapter II of "Algebraic geometry" by Hartshorne. We define finite morphisms, and attempt to sort out the three different definition of quasifinite morphisms in the literature.
From playlist Algebraic geometry II: Schemes
algebraic geometry 23 Categories
This lecture is part of an online algebraic geometry course, based on chapter I of "Algebraic geometry" by Hartshorne. It gives a quick review of category theory as background for the definition of morphisms of algebraic varieties.
From playlist Algebraic geometry I: Varieties
Schemes 21: Separated morphisms
This lecture is part of an online algebraic geometry course on schemes, based on chapter II of "Algebraic geometry" by Hartshorne.. We define separated and quasi-separated schemes and morphisms, give a few examples, and show that if a scheme has a separated morphism to an affine scheme the
From playlist Algebraic geometry II: Schemes
This lecture is part of an online algebraic geometry course on schemes, based on chapter II of "Algebraic geometry" by Hartshorne. We give two examples of gluing affine schemes to get non-affine schemes: the line with two origins and the projective line. We calculate the regular functions
From playlist Algebraic geometry II: Schemes
Algebraic Spaces and Stacks: Ideas
We try to give some motivation for the definitions we give in the subsequent videos.
From playlist Stacks
This lecture is part of an online course on categories. Any object of a category can be thought of as a representable functor in the category of presheaves. We give several examples of representable functors. Then we state Yoneda's lemma, which roughly that morphisms of objects are he sa
From playlist Categories for the idle mathematician
Fibered Categories, Descent Data and The Definition of a Stack. (This was the first video I made.)
From playlist Stacks
Joseph Ayoub - 2/5 Sur la conjecture de conservativité
La conjecture de conservativité affirme qu'un morphisme entre motifs constructibles est un isomorphisme s'il en est ainsi de l'une des ses réalisations classiques (de Rham, ℓ-adique, etc.). Il s'agit d'une conjecture centrale dans la théorie des motifs ayant des conséquences concrètes sur
From playlist Joseph Ayoub - Sur la conjecture de conservativité
Schemes 25: Proper morphisms and valuations
This lecture is part of an online algebraic geometry course on schemes, based on chapter II of "Algebraic geometry" by Hartshorne. We describe how to test a morphism for being proper using discrete valuation rings, and use this to show that projective morphisms are proper.
From playlist Algebraic geometry II: Schemes