On the existence of flips

Letters of a Bi-Rationalist: VII. Ordered termination

To construct a resulting model in LMMP is sufficient to prove existence of log flips and their termination for certain sequences. We prove that LMMP in dimension $d-1$ and termination of terminal log flips in dimension $d$ imply, for any log pair of dimension $d$, the existence of a {\em resulting} log model: a strictly log minimal model or a strictly log terminal Mori log fibration, and imply existence of log flips in dimension $d+1$. As consequence, we prove existence of a resulting model of 4-fold log pairs, existence of log flips in dimension 5, and some fragments of Geography of log model…

On Shokurov's Log Flips: The 3-dimensional Case

This is a survey on the recent fundamental paper by V.V. Shokurov on the existence of log flips.

Existence of log canonical flips and a special LMMP

Let $(X/Z,B+A)$ be a $\Q$-factorial dlt pair where $B,A\ge 0$ are $\Q$-divisors and $K_X+B+A\sim_\Q 0/Z$. We prove that any LMMP$/Z$ on $K_X+B$ with scaling of an ample$/Z$ divisor terminates with a good log minimal model or a Mori fibre space. We show that a more general statement follows from the ACC for lc thresholds. An immediate corollary of these results is that log flips exist for log canonical pairs.

Existence of flips and minimal models for 3-folds in char p

We will prove the following results for $3$-fold pairs $(X,B)$ over an algebraically closed field $k$ of characteristic $p>5$: log flips exist for $\Q$-factorial dlt pairs $(X,B)$; log minimal models exist for projective klt pairs $(X,B)$ with pseudo-effective $K_X+B$; the log canonical ring $R(K_X+B)$ is finitely generated for projective klt pairs $(X,B)$ when $K_X+B$ is a big $\Q$-divisor; semi-ampleness holds for a nef and big $\Q$-divisor $D$ if $D-(K_X+B)$ is nef and big and $(X,B)$ is projective klt; $\Q$-factorial dlt models exist for lc pairs $(X,B)$; terminal models exist for klt pair…

Mld's vs thresholds and flips

Minimal log discrepancies (mld's) are related not only to termination of log flips, and thus to the existence of log flips but also to the ascending chain condition (acc) of some global invariants and invariants of singularities in the Log Minimal Model Program (LMMP). In this paper, we draw clear links between several central conjectures in the LMMP. More precisely, our main result states that the LMMP, the acc conjecture for mld's and the boundedness of canonical Mori-Fano varieties in dimension $\le d$ imply the following: the acc conjecture for $a$-lc thresholds, in particular, for canonic…

Existence of minimal models for varieties of log general type II

We prove the existence of pl-flips.

Minimal models, flips and finite generation : a tribute to V.V. SHOKUROV and Y.-T. SIU

In this paper, we discuss a proof of existence of log minimal models or Mori fibre spaces for klt pairs $(X/Z,B)$ with $B$ big$/Z$. This then implies existence of klt log flips, finite generation of klt log canonical rings, and most of the other results of Birkar-Cascini-Hacon-McKernan paper.

Letters of a Bi-Rationalist IV: Geometry of log flips

For a birational log Fano contraction, it is conjectured an inequality between the dimension of its exceptional locus and the minimal log discrepancy over the locus. The conjecture follows from the existence of the flip for the contraction and another conjecture about the maximum of minimal log discripancy in given dimension; in particular, it holds in small dimensions (up to 4), and some special cases. It is illustrated by some examples.

Log minimal model program for the moduli space of stable curves: The second flip

We prove an existence theorem for good moduli spaces, and use it to construct the second flip in the log minimal model program for the moduli space of stable curves. In fact, our methods give a uniform, self-contained construction of the first three steps of the log minimal model program for the moduli spaces of stable pointed curves.

New outlook on the Minimal Model Program, II

We prove that the finite generation of adjoint rings proved in [Cascini and Lazić] implies all the foundational results of the Minimal Model Program: the Rationality, Cone and Contraction theorems, the existence of flips, and termination of flips with scaling in the presence of a big boundary.

正特征下三维广义对的极小模型的存在性

Existence of minimal models for threefold generalized pairs in positive characteristic

研究在特征\(p>5\)代数闭域\(\mathbb{K}\)上三维伪有效NQC lc广义对极小模型的存在性，通过\(\leq3\)维lc阈值的ACC和\(\leq2\)维广义对的全局ACC，证明其翻转终止性，提供不依赖非零定理的新证明。

关于 Kähler 3-fold 的极小模型纲领

On the Minimal Model Program for Kähler 3-folds

本文证明了紧 Kähler 簇在维度 n 下的 pl-flipping、除子收缩及 pl flip 的存在性，并给出了维度 3 下锥定理、flip 及极小模型存在的自包含证明。

Existence of good moduli spaces for A_k-stable curves

We prove a general criterion for an algebraic stack to admit a good moduli space. This result may be considered as a weak analog of the Keel-Mori theorem, which guarantees the existence of a coarse moduli space for a separated Deligne-Mumford stack. We apply our result to prove that the moduli stacks of A_k and A_k^+-stable curves admit good moduli spaces. In forthcoming work, we will prove that these moduli spaces are projective and use them to construct the second flip in the log minimal model program for M_g.

The LMMP for log canonical 3-folds in char $p$

We prove that one can run the log minimal model program for log canonical $3$-fold pairs in characteristic $p>5$. In particular we prove the Cone Theorem, Contraction Theorem, the existence of flips and the existence of log minimal models for pairs with log divisor numerically equivalent to an effective divisor. These follow from our main results, which are that certain log minimal models are good.

MMP for algebraically integrable foliations

We show that termination of flips for $\mathbb Q$-factorial klt pairs in dimension $r$ implies existence of minimal models for algebraically integrable foliations of rank $r$ with log canonical singularities over a $\mathbb Q$-factorial klt projective variety.

On the log minimal model program for $3$-folds over imperfect fields of characteristic $p>5$

We prove that many of the results of the LMMP hold for $3$-folds over fields of characteristic $p>5$ which are not necessarily perfect. In particular, the existence of flips, the cone theorem, the contraction theorem for birational extremal rays, and the existence of log minimal models. As well as pertaining to the geometry of fibrations of relative dimension $3$ over algebraically closed fields, they have applications to tight closure in dimension $4$.

关于三维簇上秩一叶状结构的极小模型计划（MMP）

On the MMP for rank one foliations on threefolds

本文证明 Q-因子射影 klt 三维簇上秩一对数典范叶状配对存在翻转，从而推广了三维秩一叶状结构极小模型的存在性结果。

代数积分可积 foliation 在 klt 变形上的最简模型程序

Minimal model program for algebraically integrable foliations on klt varieties

本文研究了klt变种上的lc代数积分可积foliation的最简模型程序，证明了基点自由定理、收缩定理和翻转的存在性，展示了Q-因子理klt变种的Mori梦空间性质。

The Kahler-Ricci flow through singularities

We prove the existence and uniqueness of the weak Kahler-Ricci flow on projective varieties with log terminal singularities. It is also shown that the weak Kahler-Ricci flow can be uniquely continued through divisorial contractions and flips if they exist. We then propose an analytic version of the Minimal Model Program with Ricci flow.

三维簇上余秩一叶状结构的极小模型计划（MMP）

MMP for co-rank one foliations on threefolds

该研究针对Q-阶乘射影三维簇上余秩一的F-dlt叶状配对，证明了翻转存在、特殊终止、基点自由定理及对数一般型下极小模型存在，推导了相关修正与奇点性质，验证了数值平凡情形的丰饶性，推进了叶状结构极小模型计划研究。