Questions tagged [minimal-model-program]

minimal model program is part of the birational classification of algebraic varieties.

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How can I describe in explicit geometric terms the (in general non-complete) linear system?

Let $\varphi\!: S \to S^\prime$ be a birational morphism of projective non-singular irreducible surfaces over a (algebraically closed) field $k$ and let $D \in \mathrm{Div}(S)$. Also, let $\big(\...
Dimitri Koshelev's user avatar
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Section ring $R(X,D)$ of $D$ is finitely generated if $\kappa (X,D) \leq 1$

In the remark on the bottom of page 5 of this paper, the author states that It is well-known fact that the algebra of a Divisor $D$ with $\kappa (X,D) \leq 1$ is finitely generated over $k$. In ...
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Map associated to linear system onto curve is morphism

In Mumford's first paper on Surfaces in char $p$ [1], part 2 Step (II), he wants to show that, given an indecomposable curve of canonical type $D$ on a smooth projective surface $F$ with $p_g(F)=0, ...
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Minimal Model Program for sub-lc pairs

In many articles of the minimal model program the authors work with sub-lc pairs instead of lc-pairs. In other words, they consider non-necesarilly effective boundary divisors $B$. Is it expected (...
Joaquín Moraga's user avatar
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Pseudo-effective divisor which is not nef in any birational model

Let $X$ be a smooth complex projective algebraic variety and let $D$ be a $\mathbb{Q}$-Cartier pseudo-effective divisor on $X$. Lets say that $D$ is birationally nef if there exists a birational ...
Joaquín Moraga's user avatar
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Finding basis of cohomology of a symplectic manifold by using Symplectic Minimal Model Program

My question is about Floer theory via symplectic surgery of Minimal Model program for finding basis of cohomology. Motivation: Perelman for solving Thurston's Geometrization Conjecture used some sort ...
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Finiteness of models around a non-pseudo-effective ray

Let $(X,\Delta) $ a klt pair and $\rho $ a numerical class of divisor that is not contained in the pseudo-effective cone. Let $(X,\Delta_i)$ be a sequence of klt pairs such that $K_X+\Delta_i$ is not ...
Joaquín Moraga's user avatar
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relative tangent sheaf

Let $f:X\rightarrow Y$ be a surjective birational morphism of varieties. Suppose the center of the birational morphism is $Z$ and $f:f^{-1}(Z)\rightarrow Z$ is a $\mathbb{P}^n$-bundle. Consider the ...
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Bertini's type theorems over imperfect fields

Let $X$ be a projective variety over an imperfect (hence infinite and char(k)=p>0) field $k$. If the local rings of $X$ are all regular, then can we say that a general hyperplane section $H$ is also ...
Omprokash Das's user avatar
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Deminormal and Gorenstein

Let X be an irreducible deminormal variety such that the normalisation is Gorenstein. Does it follow that X is also Gorenstein? for deminormal definition, see https://arxiv.org/pdf/1506.02002.pdf
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dualizing sheaf of deminormal variety

Let X be a deminormal variety (over Char 0). Then is it true that the dualizing sheaf is divisorial? Please provide a reference..
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A question about the dimension of a relatively ample divisor

Suppose $f: Y \to Z$ is a projective morphism of smooth varieties with connected fibers. If an effective divisor $H$ on $Y$ is relatively ample over $Z$, and $\dim Y >\dim Z$, is $h^0(Y, mH)>1$ ...
Li Yutong's user avatar
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Kuranishi family and smoothing of Calabi-Yau n-fold

Consider $X$ be a Calabi-Yau n-fold with at most one ordinary double point singularity. Suppose $X$ is smoothable. Then it is known that the Kuranishi family of $X$ is a smoothing of $X$. Now, ...
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Example of a non-algebraic singularity II

In an answer of this MO question, Frank Loray constructed an example of analytic singularity which is not algebraic. On the other hand, as I learned from one of Joël's comments in that question, ...
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Nefness property for symplectic equivalency of Moishezon manifolds

Definition:Two symplectic manifolds $(X,\omega_X)$ and $(Y,\omega_Y)$ are defined to be symplectically equivalent if there exists a diffeomorphism $\phi:X\to Y$ such that $\phi^∗ω_Y$ is in the same ...
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Moishezon projectivity criterion for Moishezon spaces with canonical singularites

A Moishezon manifold is projective if and only if it is Kähler. This is no longer true for a singular Moishezon space. Moishezon proved a projectivity criterion for Moishezon spaces with isolated ...
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Picard number of a general fiber of a fiber contraction

Suppose in the last step of a MMP, we obtain a Mori fiber space $f: X \to Z$, and let $F$ be a general fiber of $f$, then is the Picard number $\rho(F)$ of $F$ equal to $1$? Notice that the relative ...
Li Yutong's user avatar
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Bogomolov–Miyaoka–Yau inequality for minimal varieties with intermediate Kodaira dimension $0<\kappa (X)<\dim X$

From the differential geometric proof of Yau and the algebraic proof of Miyaoka for minimal varieties of general type $\kappa (X)=\dim X$, we know that $$(-1)^nc_1^n(X)\leq (-1)^n\frac{2(n+1)}{n} c_1^...
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2 votes
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Castelnuovo and Artin contractibility criteria for families

In the course of a proof, I need some version of Castelnuovo and Artin's contractibility criteria for a family of surfaces. Say I have a family (flat is probably needed, in order to compare ...
Stefano's user avatar
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rational effective implies effective?

Let $X$ be a weak del pezzo surface, I Wonder whether the following statment is true: Let $L$ be a line bundle on $X$, then $h^0(L)=0$ implies $h^0(nL)=0$ for all $n\geq 1$.
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Advantage of discrepancy

In the definition of Minimal model of projective variety, some authors use of discrepancy, and some others omit this condition. I am wondering to know the advantage of discrepancy In the definition of ...
Julien K's user avatar
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A theorem about log Calabi-Yau pairs

Let $X$ be a normal variety with $\mathbb Q$-Cartier divisor $D$, such that $K_X+D$ is $\mathbb Q$-Cartier. Let $(X,D)$ is log Calabi-Yau pair, i.e, $K_X+D\sim_\mathbb Q0$. (For example take $ X$ be a ...
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Adjunction formula on pair

Assume $X$ be a normal projective variety with $\mathbb Q$-Cartier divisor $D$, then can we extend adjunction formula on pair $(X,D)$?
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holomorphic fiber space when fibers are of general type

Let $\pi:X\to S$ be a holomorphic fibre space, then from birational geometry, the canonical divisor of general fibers are ample or trivial. When fibers are of general type?
Alon's user avatar
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$L^2$ extension theorem

Is there an Ohsawa-Takagushi $L^2$-Extension theorem for Kahler manifolds? For projective varieties Siu-Paun proved: Let $\pi \colon X \to \mathbb D$ be a projective family of $n$-folds and $X_0$ be ...
pickasa's user avatar
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Top self-intersection of the canonical divisor of a terminalization

Let $(X,\Delta)$ be a $n$-dimensional log canonica model, and let $Y\rightarrow (X,\Delta)$ be a log terminalization (meaning that $Y$ is the model obtained when we take a log resolution $\pi \colon ...
Joaquín Moraga's user avatar
4 votes
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164 views

A question about potentially birational divisor

I am reading the paper "On the birational automorphisms of varieties of general type", and I have a question about the property of potentially birational divisor. Definition (potentially birational ...
Li Yutong's user avatar
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References for the minimal model program

What are some references for a beginning graduate student in algebraic geometry to learn about the minimal model program? I'm not thinking about entering this field, but rather I just want to know ...
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Quasi-projectivity of the moduli space of Kahler-Einstein Fano varities and vanishing Lelong number

Chi Li, Xiaowei Wang, Chenyang Xu proved the Quasi-projectivity of the moduli space of smooth Kahler-Einstein Fano manifolds. My question is about when central fibre $X_0$ along Kahler-Einstein Fano ...
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$m$-th root of holomorphic section of direct image of relative line bundle

Question edited after the answer of Sándor Kovács: Let $f:X\to B$ be a holomorphic fibre space of smooth projective varieties which $f$ is relatively semi-ample and take $\mu$ as $m$-th root of ...
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2 votes
1 answer
622 views

A Decomposition for Iitaka fibration

Let $\pi: X\to Y$ be an Iitaka fibration of projective varieties $X,Y$, then is there always the following decomposition $$K_Y+\frac{1}{m!}\pi_*\mathcal O_X(m!K_{X/Y})=P+N$$ where $P$ is ...
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$C^\infty$-curvature of Kawamata's singular hermitian metric

Let $X,Y$ are two projective varieties and $f:X\to Y$ is an Iitaka fibration. Consider the following singular hermitian metric $$h(\sigma,\sigma)=\left(\int_{X_y}|\sigma|^{\frac{2}{m!}}\right)^{m!}$$ ...
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1 vote
1 answer
390 views

Central fibre singularities

Let $f:X\to Y $ be a proper surjective holomorphic fibre space where $X,Y $ are projective varieties. If the central fibre $X_0$ has at worst log terminal singularities, then can we say that all ...
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4 votes
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Some questions on Kontsevich's moduli space

Motivation: Work of Eisenbud, Harris, and Mumford shows that $\mathcal M_g$ is of general type when $g≥24$. Moreover, by Logan's function $f(g)$ , $\overline {\mathcal M_{g,n}}$ is of general type for ...
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Some examples where the plurigenera are nonconstant, when the fibres have worse singularities than canonical

Let start with a definition Invariance of plurigenera: Choose $m$ large enough so that $mK_F$ has a non-zero global section for some fibre $F$. For any fibre $F$, we have $K_F = K_{X/D}~_{|F}$. So ...
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local description of $\mathbb{P}^2$-fibrations over $\mathbb{P}^1$

Let $X$ be a rational threefold (over the field of complex numbers) with terminal singularities. It is well-known that $X$ has only finitely many singular points $x_1,x_2, \ldots,x_n$. To be more ...
sabrebooth's user avatar
6 votes
1 answer
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Generic Smoothness Type of Results in Positive Characteristic

Let $f:X\to Y$ be a surjective morphism between two projective varieties over a field of characteristic $p>0$. Also assume that $f_*\mathcal{O}_X=\mathcal{O}_Y$, and $X$ is smooth. We know that ...
Omprokash Das's user avatar
6 votes
0 answers
902 views

Restriction of the Canonical Divisor $K_X$ to a general fiber

Let $\ f:X\to Z$ be a surjective morphism between two smooth projective varieties with connected fibers $(f_*\mathcal{O}_X=\mathcal{O}_X)$. Let $F$ be a general fiber of $f$ and $\mbox{dim } F<(\...
Omprokash Das's user avatar
4 votes
1 answer
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On Q-Cartier Divisors

I have my question on Q-Cartier Weil divisor. People say $D$ is Q-Cartier divisor if $nD$ is Cartier for some $n \geq 1$. Especially for $n > 1$, I have never seen the `rigorous' definition of $...
Pierre MATSUMI's user avatar
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Finite generation of certain $\mathcal{O}_X$-algebra

It is proved in this paper by Kawamata (Theorem 6.1) that for a 3-dimensional normal algebraic variety $X$ which has at most canonical singularities, and a Weil divisor $D$ on it, the $\mathcal{O}_X$-...
Li Yutong's user avatar
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3 votes
1 answer
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Run MMP between varieties of isomorphic in codimension 1

Let $X, Y$ be two birational projective varieties which are isomorphic in codimension 1. Suppose $H$ is an ample divisor on $Y$, and $H'$ be its strict transform on $X$, suppose we can run MMP with ...
Li Yutong's user avatar
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4 votes
1 answer
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A question about running MMP with scaling

Let $\pi:X \to U$ be a projective morphism, and $(X, \Delta = A + B)$ be a KLT pair, where $A$ is a general ample divisor and $B$ is effective. Suppose $K_X + \Delta$ is not nef (over $U$) and there ...
Li Yutong's user avatar
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5 votes
1 answer
465 views

Number of minimal models of a surface

I would like to know if the following statement is true or false: Given a non-singular complex projective surface $S$, it has at most a countable number of minimal models (up to isomorphism). We ...
Dubious's user avatar
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1 vote
2 answers
513 views

Decompose a big divisor as nef big divisor and effective divisor

Let $W_n$ be a set of a log pair having the following property: For any $(X, D) \in W_n$ (1)$X$ has dimensional $n$ with tirvial canonical divisor (i.e.$K_X = 0$). Moreover, $X$ is a $\mathbb{Q}$-...
Li Yutong's user avatar
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9 votes
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550 views

Singularities arising from the Minimal Model Program (an algebraic point of view)

I will start the story by the end: Is there some characterization of (some of) the singularities arising from the Minimal Model Program (canonical, terminal, log-...) in terms of commutative algebra ?...
Pedro Montero's user avatar
9 votes
1 answer
471 views

Is the number of minimal models finite

Let $X$ be a variety of general type. Assume that $\dim X = 3$. In https://eudml.org/doc/164223 it is proven that $X$ has only finitely many minimal models (i.e., only $\mathbb Q$-factorial terminal ...
Ste3an's user avatar
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3 votes
1 answer
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A covering lemma of Kawamata

In the paper "A generalization of Kodaira-Ramanujam's vanishing theorem", Kawamata states a covering lemma (Lemma 5) which is Let $X$ be a non-singular projective variety, and $D$ be a divisor with ...
Li Yutong's user avatar
  • 3,362
2 votes
1 answer
798 views

Properties of extreme rays

Let $X$ be a projective variety over $\mathbb{C}$, then the effective curves module the numerical equivalence form a cone. For my understanding, if the extreme ray $[C]$ has the property that $[C]\...
Li Yutong's user avatar
  • 3,362
0 votes
1 answer
655 views

Kawamata-Log-Terminal pairs

Let $p_1,...,p_n\in\mathbb{P}^3$ be general points, and let $\Delta\subset\mathbb{P}^3$ be a general surface of degree $d$ with points of multiplicity $m_i$ at $p_i$ for $i = 1,...,n$. Consider the ...
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6 votes
0 answers
576 views

Semistable minimal model of a $K3$-surface and the special fibre

Suppose that $K$ is a $p$-adic field, that is a field of characteristic $0$ whose ring of integers is a complete discrete valuation ring $\mathcal O_K$ and with residue field $k$ (algebraic closed) of ...
Rogelio Yoyontzin's user avatar