A Crystalline Criterion for Good Reduction on
Semi-stable K3-Surfaces over a p-Adic Field
Thesis Advisor: Prof. Adrian Iovita
J. Rogelio P´erez Buend´ıa
Concordia University
January 10 2014
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Objective:
To give a criterion for the reduction of an algebraic K3-surface over
a p-adic field in terms of its p-adic ´etale cohomology.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Objective:
To give a criterion for the reduction of an algebraic K3-surface over
a p-adic field in terms of its p-adic ´etale cohomology.
The desired Criterion
A K3-surface over a Local field with semistable reduction has good
reduction if and only if its second ´etale cohomology group is crystalline.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Layout
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Notations:
Fix a prime number p and let Qp the field of p-adic numbers. Consider:
1 k be a perfect field of characteristic p.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Notations:
Fix a prime number p and let Qp the field of p-adic numbers. Consider:
1 k be a perfect field of characteristic p.
2 ¯k be a fix algebraic closure.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Notations:
Fix a prime number p and let Qp the field of p-adic numbers. Consider:
1 k be a perfect field of characteristic p.
2 ¯k be a fix algebraic closure.
3 W := W (k) the ring of Witt vectors with coefficients in k
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Notations:
Fix a prime number p and let Qp the field of p-adic numbers. Consider:
1 k be a perfect field of characteristic p.
2 ¯k be a fix algebraic closure.
3 W := W (k) the ring of Witt vectors with coefficients in k
4 K0 = Frac(W ) its field of fractions. It is an unramified extension of
Qp.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Notations:
Fix a prime number p and let Qp the field of p-adic numbers. Consider:
1 k be a perfect field of characteristic p.
2 ¯k be a fix algebraic closure.
3 W := W (k) the ring of Witt vectors with coefficients in k
4 K0 = Frac(W ) its field of fractions. It is an unramified extension of
Qp.
5 K = K0 if k is ifninite or K be a finite extension of K0 if
[k : Fp] < ∞.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Notations:
Fix a prime number p and let Qp the field of p-adic numbers. Consider:
1 k be a perfect field of characteristic p.
2 ¯k be a fix algebraic closure.
3 W := W (k) the ring of Witt vectors with coefficients in k
4 K0 = Frac(W ) its field of fractions. It is an unramified extension of
Qp.
5 K = K0 if k is ifninite or K be a finite extension of K0 if
[k : Fp] < ∞.
6 OK the ring of integers of K.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Notations:
Fix a prime number p and let Qp the field of p-adic numbers. Consider:
1 k be a perfect field of characteristic p.
2 ¯k be a fix algebraic closure.
3 W := W (k) the ring of Witt vectors with coefficients in k
4 K0 = Frac(W ) its field of fractions. It is an unramified extension of
Qp.
5 K = K0 if k is ifninite or K be a finite extension of K0 if
[k : Fp] < ∞.
6 OK the ring of integers of K.
7 π be a (fixed) uniformizer. So mK = πOK and
k = OK /πOK = W /pW .
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
K3-surfaces
Definition
A K3-surface over K is a smooth proper surface XK −→ Spec(K) such
that
1 q := H1
(XK , OXK
) = 0 and
2 ωXK
OXK
. Equivalently KX = 0.
where ωXK
stands for the canonical sheaf and KX its canonical divisor.
This definition is independent of the field K, so we can consider this
definition for K = C and we get complex algebraic K3-surfaces.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Examples:
K3-surfaces were named by Andr´e Weil in honour of three algebraic
geometers, Kummer, K¨ahler and Kodaira, and the mountain K2 in
Kashmir.
Figure: A quartic in P3
K given by x2
y2
+ y2
z2
+ z2
x2
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Examples
Let S be a non-singular sixtic curve in P2
k where k is a field and consider
a double cover i.e., a finite generically ´etale morphism, π : X → P2
k which
is ramified along S. Then X is a K3 surface.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Example
Complete intersections: Let X be a smooth surface which is a complete
intersection of n hypersurfaces of degree d1, . . . , dn in Pn+2
over a field k.
The adjunction formula shows that Ω2
X/k
∼= OX (d1, . . . , dn − n − 3). So a
necessary condition for X to be a K3 surface is d1 + . . . + dn = n + 3.
The first possibilities are:
n = 1 d1 = 4
n = 2 d1 = 2, d2 = 3
n = 3 d1 = d2 = d3 = 2.
For a complete intersection M of dimension n one has that
Hi
(M, OM (m)) = 0 for all m ∈ Z and 1 ≤ i ≤ n − 1. Hence in those
three cases we have H1
(X, OX ) = 0 and therefore X is a K3 surface.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Example
Let A be an abelian surface over a field k of characteristic different from
2. Let A[2] be the kernel of the multiplication by-2-map, let π : ˜A → A
be the blow up of A[2] and let ˜E be the exceptional divisor. The
automorphism [−1]A lifts to an involution [−1]˜A on ˜A. Let X be the
quotient variety of ˜A by the group of automorphisms {id˜A, [−1]˜A} and
denote by ι : ˜A → X the quotient morphism. It is a finite map of degree
2. We have the following diagram of morphisms over k. The variety X is
a K3 surface and it is called the Kummer surface associated to A.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Semistable K3-surfaces
Definition
XK has semistable reduction if it has a semi-stable model:
XK
//

X

Spec(K) // Spec(OK)
that is a proper (flat) model X → Spec(OK) whose special fibre ¯X is
smooth over k or ´etale locally a normal crossing divisor.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Good reduction
If the special fibre ¯X → Spec(k) of such a model X is smooth, then we
say that XK has good reduction.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Layout
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
p-adic representations
Let GK := Gal(K, K) be the absolute Galois group of K.
Definition
A p-adic representation V of GK is a finite dimensional Qp-vector space
with a continuous action of GK .
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Examples of p-adic representations
The main example:
Main example
The ´etale cohomology of a K3-surface. Indeed, in general we have that if
X is a proper and smooth variety over K, then
Hi
´et(X¯K , Qp)
is a p-adic representation of GK .
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Examples of p-adic representations
The main example:
Main example
The ´etale cohomology of a K3-surface. Indeed, in general we have that if
X is a proper and smooth variety over K, then
Hi
´et(X¯K , Qp)
is a p-adic representation of GK .
Tate modules of abelian varieties.
The r-Tate twists of Qp, Qp(r).
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Ring of periods
In order to study the p-adic representations, Fontaine defines what we
know as ring of periods, which are topological Qp-algebras B (or B•),
with a continuous linear action of GK and some additional structures
which are compatible with the action of GK (for example the monodromy
operator N, Frobenius, filtrations).
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Poincar´e duality
For a smooth and projective variety X of dimension n over the complex
numbers C, we have the Betti cohomlogy Hi
(X(C), Z).
By Poincar´e duality we have that:
H2n−i (X, C) Hi
(X(C), C).
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Complex periods
Also we have a perfect pairing given by the periods:
Hi
dR(X(C)/C) × H2n−i (X(C), C) −→ C
(ω, λ) →
λ
ω.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Comparison isomorphism
We have a natural comparison isomorphism:
Hi
dR(X(C)/C) Hi
(X(C), C).
We remark that in order to have this isomorphism it is very important to
have coefficients in C (for example, this is not an isomorphism over Q).
In this sense C is a ring of periods (it contains all the periods λ
ω).
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
The p-adic case of Cp
We denote by
Cp = ˆ¯K
the p-adic completion of ¯K.
We want analogous comparison isomorphisms in the p-adic cases.
However the situation is not as easy as in the complex case, mainly
because Cp does not have enough periods.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Fontaine’s Idea
The original idea of Fontaine was to construct these ring of periods, in
order to be able to have analogous comparison isomorphism between the
different cohomologies in p-adic settings.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
B•
Examples of this rings are
1 BHT := q∈Z Cp(q) B Hodge-Tate. is a graded C p-algebra with
GK -action rescts gradings and BGK
HT = K.
2 BdR : B de Rham is a complete discrete valuation field over K with
residue field Cp. It contains K (but not Cp). It has an action of GK
and a filtration by its valuation, and its graded quotient
gri
BdR = Cp(i)
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Bcris
Bcris: B crys is an algebra over K0 and a GK -stable subring of BdR . It
contains K0 but not K. We have a filtration coming from form BdR , a
σ-semilinear injective GK -equivariant endomorphism φ (Frobenius
endomorphism). BGK
cis = K0.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Bst
Bst: B semistable is an algebra over K0 and has a GK -action. It contains
Bcris and KO but not K The Frobenius of Bcris extends to Bst and has a
Bcris-derivation
N : Bst −→ Bst. Nφ = pφN
and
BGK
st = K0, BN=0
st = Bcris.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Dieudonn´e Modules
These rings are such that the BGK
-modules
DB (V ) := (B ⊗Qp
V )GK
give us (or expected to give us) good invariants for V . For example
comparison isomorphisms for the p-´adic ´etale cohomology and de Rham
cohomologie or crystalline cohomology or nice criterion for good
reduction of varieties.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
B-admissible
Let L = BGK
.
Definition
A p-adic representation V is B-admissible, if
dimL DB (V ) = dimQp
V .
Definition
A p-adic representation V , is crystalline (semistable, Hodge-Tate,
semistable) if V is Bcris-admissible (B•-admissible).
B-admissibility translates to isomorphisms which are analogous to the
comparison isomorphisms in the complex case.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Fontaine has defined several subcategories of the category of all p-adic
representations, denoted by RepGK
.
This categories are formed by the property of being B-admissible objects.
So for any of the period rings B we have a subcategory of the category of
p-adic representations denoted by RepB . These categories satisfy proper
contention relations as follows:
RepBcris
⊂ RepBst
⊂ RepBdR
⊂ RepBHT
⊂ RepGK
.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
C•-conjectures
Let XK be a proper smooth variety over K.
CHT : The Hodge-Tate conjecture. There exists a canonical
iomorphism, which is compatible with the Galois action.
Cp ⊗Qp Hm
et (X¯K , Qp)
0≤i≤m
Cp(−i) ⊗K Hm−i
(X¯K , Ωi
XK /K ).
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
C•-conjectures
Let XK be a proper smooth variety over K.
CHT : The Hodge-Tate conjecture. There exists a canonical
iomorphism, which is compatible with the Galois action.
Cp ⊗Qp Hm
et (X¯K , Qp)
0≤i≤m
Cp(−i) ⊗K Hm−i
(X¯K , Ωi
XK /K ).
CdR : The de Rham conjecture. There exist a conaonical
isomorphism, which is compatible with Galois action and filtrations.
BdR ⊗Qp
Hm
et (X¯K , Qp) BdR ⊗K Hm
dR (XK /K).
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
C•-conjectures
Ccris: The Crystalline conjecture. Let X be a proper smooth model
of XK over OK . Let ¯X be the special fibre of X. There exist a
canonical isomorphism which is compatible with the Galois action,
and Frobenius endomorphism.
Bcris ⊗Qp
Hm
´et (X¯K , Qp) Bcris ⊗W Hm
crys(¯X/W )
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
C•-conjectures
Ccris: The Crystalline conjecture. Let X be a proper smooth model
of XK over OK . Let ¯X be the special fibre of X. There exist a
canonical isomorphism which is compatible with the Galois action,
and Frobenius endomorphism.
Bcris ⊗Qp
Hm
´et (X¯K , Qp) Bcris ⊗W Hm
crys(¯X/W )
Barthelo-Ogus isomorphism:
K ⊗W Hm
crys(¯X/W ) Hm
dR (XK /K).
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Cst conjecture
1 Cst: The semistable conjecture: Let X be a proper semistable model
of XK over OK . Let Y be the special fiber of X, and MY be a
naural log-structure on Y . There is a canonical isomorphsim,
compatible with Galois action, Frobenius and operator N.
Bst ⊗Qp
Hm
et (XK , Qp) Bst ⊗W Hm
log −crys((Y , MY ), (W , O∗
))
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Cst conjecture
1 Cst: The semistable conjecture: Let X be a proper semistable model
of XK over OK . Let Y be the special fiber of X, and MY be a
naural log-structure on Y . There is a canonical isomorphsim,
compatible with Galois action, Frobenius and operator N.
Bst ⊗Qp
Hm
et (XK , Qp) Bst ⊗W Hm
log −crys((Y , MY ), (W , O∗
))
2 Hydo-Kato isomorphism
K ⊗W Hm
log −crys((Y , MY ), (W , O∗
)) HdR (XK /K)
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
History
For X/K a proper smooth variety over K.
Fontaine: Proved that Tate modules V = TpA ⊗Zp Qp of abelian varieties A are de Rham
and that DdR(V ) (HdR(X/K))v
.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
History
For X/K a proper smooth variety over K.
Fontaine: Proved that Tate modules V = TpA ⊗Zp Qp of abelian varieties A are de Rham
and that DdR(V ) (HdR(X/K))v
.
Fontaine and Messing: Proved the comparison theorem for Hi
´et(X¯K , Qp) for i ≤ p − 1 and
K/Qp finite unramified.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
History
For X/K a proper smooth variety over K.
Fontaine: Proved that Tate modules V = TpA ⊗Zp Qp of abelian varieties A are de Rham
and that DdR(V ) (HdR(X/K))v
.
Fontaine and Messing: Proved the comparison theorem for Hi
´et(X¯K , Qp) for i ≤ p − 1 and
K/Qp finite unramified.
Kato, Hydo Tsuji: Extended these results to finally prove that one can recover Hi
dR(X/K)
from the data of V = Hi
´et(X¯K , Qp) as a p-adic representation.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
History
For X/K a proper smooth variety over K.
Fontaine: Proved that Tate modules V = TpA ⊗Zp Qp of abelian varieties A are de Rham
and that DdR(V ) (HdR(X/K))v
.
Fontaine and Messing: Proved the comparison theorem for Hi
´et(X¯K , Qp) for i ≤ p − 1 and
K/Qp finite unramified.
Kato, Hydo Tsuji: Extended these results to finally prove that one can recover Hi
dR(X/K)
from the data of V = Hi
´et(X¯K , Qp) as a p-adic representation.
Tsuji, Niziol, Faltings: Proved that if X is semistable, then V is Bst -admissible and that V
is crystalline if V has good reduction and BdR otherwise.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
For abelian varieties
For Abelian varieties, Bcris and Bst are exactly what it takes to decide:
whether A has good reduction or semistable reduction.
Crystalline criterion for abelian varieties:
Coleman-Iovita Breuil: A has good reduction if and only if V is
crystalline. A has semistable reduction if and only if V is semistable.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
My Thesis problem
Crystalline criterion for K3 surfacess:
Let X be a K3 surface over a p-adic field K with semistable reduction. X
has good reduction (¯X → Spec(k) is smooth) if and only if
V := H2
´et(X¯K , Qp)
is Crystalline (Bcris-admissible).
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
One side is Falting’s result:
Remember that
RepBcris
⊂ RepBst
Since X has semistable reduction, then V is Bst-admissible. If X has
good reduction, then by Falting’s result, V is Bcris-admissible.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Results of Y. Matsumoto
Theorem
Let K be a local field with residue characteristic p = 2 and X a Kummer
surface over K. Assume that X has at least one K-rational point. If
H2
et(X¯K , Qp) is crystalline, then XK has good reduction for some finite
unramified extension K /K.
Theorem
Let K be a local field with residue characteristic p = 2, 3, and Y a K3
surface over K with Shioda-Inose structure of product type. If
H2
et(YK , Qp) is crystalline, then YK has good reduction for some finite
extension K /K of ramification index 1, 2, 3, 4 or 6.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Main tool
The main tooll is what we call p-adic logarithmic degenerations of a
K3-surface. These will be p-adic analogous of degeneration of K3
surfaces over the complex numbers constructed via degenerations.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Complex degenerations of K3-surfaces
Definition
Over the complex numbers C, a semistable degeneration of a
K3-surface X is a proper flat and surjective morphism
π : X(C) → ∆
over the open disc, whose general fibre Xt = π−1
(t), for t = 0 is a
smooth K3-surface and X0 is reduced with normal crossings.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Modification of a degeneration
Definition
A modification of π : X(C) → ∆ is a degeneration of surfaces
π : X(C) → ∆ such that there exists a birational map
φ : X(C) → X (C) given an isomorphism form
(X(C) − X0) −→ (X (C) − X0) and such that the diagram:
X(C)
φ
//
π

X (C)
π
||
∆
commutes.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Kulikov degenerations
We have the following theorem:
Theorem (Kulikov, Persson, Pinkham)
Let π : X(C) → ∆ be a semistable degeneration of a K3-surface, then
there exists a modification π : X (C) → ∆ such that the canonical
divisor of the total space X (C) is trivial.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Kulikov degenerations
We have the following theorem:
Theorem (Kulikov, Persson, Pinkham)
Let π : X(C) → ∆ be a semistable degeneration of a K3-surface, then
there exists a modification π : X (C) → ∆ such that the canonical
divisor of the total space X (C) is trivial.
A degeneration with trivial canonical divisor is called a good
degeneration or a Kulikov degeneration.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Kulikov criterion
Theorem
Let X(C) → ∆ be a good degeneration of a K3-surface. The degenerate
fibre X0 is one of the following three types:
I. X0 is a nonsingular K3 surface.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Kulikov criterion
Theorem
Let X(C) → ∆ be a good degeneration of a K3-surface. The degenerate
fibre X0 is one of the following three types:
I. X0 is a nonsingular K3 surface.
II. X0 = ∪n
i=1Vi where the Vi are rational surfaces and V2, . . . , Vn−1 are
elliptic ruled surfaces.
III. X0 = ∪n
i=1Vi where all the Vi are rational surfaces.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
In therms of monodromy
Moreover, the three cases can be distinguished from each other by means
of the monodromy T acting on H2
(Xt, Z):
For Type I we have N := ln T = 0 that is T = id.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
In therms of monodromy
Moreover, the three cases can be distinguished from each other by means
of the monodromy T acting on H2
(Xt, Z):
For Type I we have N := ln T = 0 that is T = id.
For Type II, N = 0 but N2
= 0.
For Type III, N2
= 0 but N3
= 0
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Layout
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
The plan:
We need:
A p-adic semistable degeneration of our K3-surface.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
The plan:
We need:
A p-adic semistable degeneration of our K3-surface.
A monodromy operator N on the log-crystalline cohomology.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
The plan:
We need:
A p-adic semistable degeneration of our K3-surface.
A monodromy operator N on the log-crystalline cohomology.
We relate it with the monodromy operator on
Dst(H2
et(X¯K , Qp)) H2
log−cris(XK /W ) appearing on Fontain’s
theory.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
The plan:
We need:
A p-adic semistable degeneration of our K3-surface.
A monodromy operator N on the log-crystalline cohomology.
We relate it with the monodromy operator on
Dst(H2
et(X¯K , Qp)) H2
log−cris(XK /W ) appearing on Fontain’s
theory.
By p-adic Hodge theory if H2
´et(X¯K , Qp) is crystalline then N = 0.
Indeed BN=0
st = Bcris and Dst(V )N=0
= Dcris(V ) , so if a p-adic
representation is crystalline we most have N = 0.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Finally we base change to the complex numbers and use Kulikov’s
classification theorem to deduce that our crystalline K3-surface has good
reduction.
Here we use the Deligne’s work on the Monodromy expressed as the
residue at zero of the GM-conexion.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Layout
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Logarithmic geometry is concerned with a method of finding and
using“hide smoothness”in singular varieties.
Let X be a nonsingular irreducible complex variety, S a smooth
curve with a point s and f : X → S a dominant morphism smooth
away from s, the fiber Xs := f −1
(s) = Y1 ∪ · · · ∪ Yn reduced simple
normal crossing divisor.
ΩX/S = ΩX /f ∗
ΩS fails to be locally free at the singular points of f .
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Consider ΩX/S (log(Xs)) the sheaf of differentials with at most
logarithmic poles along the Yi , and similarly ΩS (log(s)), there is an
injective sheaf homomorphism
f ∗
ΩX (log(Xs)) −→ ΩS (log(s))
and the quotient sheaf ΩX (log(XS ))/f ∗
ΩX (log(Xs)) is locally free.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
pre-log.st
Definition
1 Let X be a scheme. A pre-log structure on X, is a sheaf of
monoids MX together with a morphism of sheaves of monoids:
α : MX −→ OX , called the structure morphism.
2 A pre-log structure is called a log structure (log.st for short) if
α−1
(O∗
X ) O∗
X via α.
3 The pair (X, MX ) is called a log scheme and it will be denoted by
X×
.
4 Morphisms are morphisms of sheaves which are compatible with the
structure morphism.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Induced log.st
We have the forgetful functor i from the category of log.st of X to the
category of pre-log.st of X by sending a log.st M in X to itself considered
as a pre-log.st i(M).
Vice-versa given a pre-log.st we can construct a log.st Mls
out of it in
such a way that ( )ls
is left adjoint of i, hence Mls
is universal.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Inverse image log.st
Definition
Let f : X → Y be a morphism of schemes. Given a log.st MY on Y we
can define a log.st on X, called the inverse image of MY , to be the log
structure associated to the pre-log.st
f −1
(MY ) → f −1
(OY ) → OX .
This is denoted by f ∗
(MY ).
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Morphisms of log-schemes
Definition
By a morphism of log-schemes X∗
−→ Y ∗
we understand a morphism of
the underlying schemes f : X → Y and a morphism f #
: f ∗
MY → MX of
log.st on X.
We denote by LSch the category of log.schemes.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
One of the main examples of interest for us is the following:
Example
Let X be a regular scheme (we can take for example a K3-surface over K
or a proper model of it). Let D be a divisor of X. We can define a log.st
M on X associated to the divisor D as
M(U) := g ∈ OX (U) : g|UD ∈ O∗
X (U  D)
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
log.st to algebraizable formal schemes
Let X be a scheme and ˆX is a formal completion of X along a closed
subscheme Y , then we have a morphism of ringed spaces:
ˆX
φ
−→ X
for which φ is the inclusion Y → X on topological spaces, and on
sheaves, it is the natural projection
OX −→ lim
←−
OX /In
= OˆX
where I is the sheaf of ideals defined by the closed immersion Y → X.
If we have a log.st on X, say M, we can give a log structure on ˆX by
taking the inverse image of the log structure M so that ˆX becomes a
log-formal scheme:
(ˆX, φ∗
M).
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
For K3-surfaces
1 When X is a proper model of a K3-surface XK , we have that the
special fibre ¯X of X is a closed divisor with normal crossings.
This divisor induces a log.st on X. We denote by X×
the log-formal
scheme obtained as in the previews paragraph; that is, by completing
X along ¯X and giving to it the inverse image log.st of X induced by
¯X.
2 Notice that we have an inclusion of ringed spaces ¯X → X×
. We
denote by ¯X×
the log-scheme obtained by giving to ¯X the inverse
image log.st of X×
.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Layout
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
p-adic degeneration
Definition
A p-adic degeneration of a K3-surface with semistalbe reduction is a proper, flat morphism of
schemes X −→ Spec(W[[t]]) with geometrically connected fibres, such that:
1 We have an isomorphism of the semistable model X of XK with the fibre Xπ of
X → Spec(W[[t]]) induced by the ring homomorphism: W [[t]] → OK ; t −→ π.
2 We have an isomorphism (compatible with the previous one) of the special fibre ¯X of the
semistable model of XK with the fibre X0 induced by the projection
W [[t]] → W [[t]]/(p, t) k = OK /πOk .
3 X → Spec(W[[t]]) is smooth in the complement of ¯X that is
(X − ¯X) −→ (Spec(W[[t]]) − Spec(k))
is smooth.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
In a diagram
Then we have commutative Cartesian diagrams:
¯X //

X //

X

Spec(k) // Spec(OK) // Spec(W[[t]])
.
Note that Spec(W[[t]]) is the analogous, in p-adic settings, of the open
unit disc ∆ in the complex numbers, and so we call Spec(W[[t]]) the
p-adic unit disc denoted by D. Then X is a family of surfaces
parametrized by the p-adic unit disc D and removing the special fibre ¯X
smooth over D∗
= D − Spec(k).
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
rig functor
1 Let Y be the fibre of f at t = 0, that is the fibre induced by the
morphism
W [[t]] → W ; t → 0.
This is a scheme over Spec(W) whose special fibre is again X.
Moreover Y is a normal crossing divisor (but now in characteristic
zero).
2 Call X = (X×
)rig, D = (D×
)rig, and f = (f ×
)rig the rigid analytic
spaces over K0.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
rigid version of the degeneration
Lemma
Under the previous settings we have:
1 X −→ Spec(K0) is smooth
2 Y := f −1
(0) = (Y×
)rig is a semistable surface over K0.
3 f |X∗ : X∗
:= (X − Y) −→ D∗
:= (D − {0}) is smooth.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Layout
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Complex of relative logarithmic differentials
Consider the complex of sheaves K·
X/D induced by the relative
logarithmic differential:
OX
d1
X/D
−−−→ OX ⊗X/K0
Ω1
X/D(log(Y))
d2
X/D
−−−→ OX ⊗X/K0
Ω2
X/D(log(Y))
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
The connection
Denote by Hi
the i-th logarithmic relative de Rham cohomology group of
X/D with coefficients in OX , i.e, it is the sheaf Rf∗(K·
X/D). For every i,
Hi
is a free OD-module with an integrable, regular-singular connection
i : Hi
−→ Hi
⊗OD
Ω1
D/K0
(log(0)).
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Monodromy
If s is a point in D, let Hi
s be the fibre of H1
at s. We now define the
monodromy Ni as the residue at 0 of this connection. That is
Ni = res0( i ).
In our case the only important value is for i = 2, so we define the
monodromy as N := N2.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Bibliography
Andreatta, F., and A. Iovita. 2012. Semistable Sheaves and Comparison Isomorphisms in the Semistable Case.
Berthelot, P. 1986. G´eom´etrie Rigide Et Cohomologie Des Vari´et´es Alg´ebriques De Caract´eristique P. Bull. Soc. Math. France.
Coleman, R., and A. Iovita. 2003. Hidden Structures on Semi-Stable Curves. Preprint.
Faltings, G. 1988. P-Adic Hodge Theory. J. Amer. Math. Soc.
Faltings, G. 1992. Crystalline Cohomology of Semistable Curves, and P-Adic Galois-Representations. Journal of Algebraic
Geometry 1, no. 1: 61–81.
Huybrechts, D. Lectures on K3-Surfaces. Unpublished Notes Available on the Author’s Website at the University of Bonn.
Kato, F. 1996. Log Smooth Deformation Theory. Tohoku Mathematical Journal.
Kato, K. 1989. Logarithmic Structures of Fontaine-Illusie. Algebraic Analysis.
Kawamata, Y., and Y. Namikawa. 1994. Logarithmic Deformations of Normal Crossing Varieties and Smoothing of Degenerate
Calabi-Yau Varieties. Inventiones Mathematicae 118, no. 1 (December): 395–409.
http://imperium.lenin.ru/ kaledin/math/pdf/kawa-naka.pdf.
Kulikov, V.S. 2007. Degenerations of K3 Surfaces and Enriques Surfaces. Mathematics of the USSR-Izvestiya.
MORRISON, D.R. 2012. The Geometry of K3 Surfaces. Cgtp.Duke.Edu. Accessed October 13.
http://www.cgtp.duke.edu/ITP99/morrison/cortona.pdf. 223.
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
Bibliography
Olsson, M.C. 2004. Semistable Degenerations and Period Spaces for Polarized K3 Surfaces. Duke Mathematical Journal 125, no.
1: 121–203.
Rizov, J. 2010. Kuga-Satake Abelian Varieties of K3 Surfaces in Mixed Characteristic. Journal F¨Ur Die Reine Und Angewandte
Mathematik 648: 13–67.
Schroeer, S. 2000. Logarithmic Deformations of Normal Crossing Enriques Surfaces in Characteristic Two. arXiv.org (May 8).
Siegfreid, B. 2012. Formal and Rigid Geometry. Ed. Werner lurkebohemart. People.Math.Jussieu.Fr. Accessed August 30.
http://people.math.jussieu.fr/ fmartin/these/G
Berger, L. 2004. An Introduction to the Theory of P-Adic Representations. Geometric Aspects of Dwork Theory 1: 255–292.
BRINON, O., and B. CONRAD. 2008. CMI SUMMER SCHOOL NOTES on P-ADIC HODGE THEORY (PRELIMINARY
VERSION) . arXiv.org.
Colmez, P. 1998. Repr´esentations P-Adiques D’un Corps Local. Proceedings of the International Congress of . . . .
Fontaine, J.M. 1982. Sur Certains Types De Representations P-Adiques Du Groupe De Galois D’Un Corps Local; Construction
D”Un Anneau De Barsotti-Tate. The Annals of Mathematics 115, no. 3: 529–577.
Serre, J.P., and M.J. Greenberg. 1979. Local Fields 191.
Fontaine, J.M. 1994. Periodes p-adiques (S´eminaire de Bures, 1988). SMF - Publications - Ast´erisque - Titles - 1994 -
J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a

A Crystalline Criterion for Good Reduction on Semi-stable $K3$-Surfaces over a $p$-Adic Field

  • 1.
    A Crystalline Criterionfor Good Reduction on Semi-stable K3-Surfaces over a p-Adic Field Thesis Advisor: Prof. Adrian Iovita J. Rogelio P´erez Buend´ıa Concordia University January 10 2014 J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 2.
    Objective: To give acriterion for the reduction of an algebraic K3-surface over a p-adic field in terms of its p-adic ´etale cohomology. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 3.
    Objective: To give acriterion for the reduction of an algebraic K3-surface over a p-adic field in terms of its p-adic ´etale cohomology. The desired Criterion A K3-surface over a Local field with semistable reduction has good reduction if and only if its second ´etale cohomology group is crystalline. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 4.
    Layout J. Rogelio P´erezBuend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 5.
    Notations: Fix a primenumber p and let Qp the field of p-adic numbers. Consider: 1 k be a perfect field of characteristic p. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 6.
    Notations: Fix a primenumber p and let Qp the field of p-adic numbers. Consider: 1 k be a perfect field of characteristic p. 2 ¯k be a fix algebraic closure. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 7.
    Notations: Fix a primenumber p and let Qp the field of p-adic numbers. Consider: 1 k be a perfect field of characteristic p. 2 ¯k be a fix algebraic closure. 3 W := W (k) the ring of Witt vectors with coefficients in k J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 8.
    Notations: Fix a primenumber p and let Qp the field of p-adic numbers. Consider: 1 k be a perfect field of characteristic p. 2 ¯k be a fix algebraic closure. 3 W := W (k) the ring of Witt vectors with coefficients in k 4 K0 = Frac(W ) its field of fractions. It is an unramified extension of Qp. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 9.
    Notations: Fix a primenumber p and let Qp the field of p-adic numbers. Consider: 1 k be a perfect field of characteristic p. 2 ¯k be a fix algebraic closure. 3 W := W (k) the ring of Witt vectors with coefficients in k 4 K0 = Frac(W ) its field of fractions. It is an unramified extension of Qp. 5 K = K0 if k is ifninite or K be a finite extension of K0 if [k : Fp] < ∞. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 10.
    Notations: Fix a primenumber p and let Qp the field of p-adic numbers. Consider: 1 k be a perfect field of characteristic p. 2 ¯k be a fix algebraic closure. 3 W := W (k) the ring of Witt vectors with coefficients in k 4 K0 = Frac(W ) its field of fractions. It is an unramified extension of Qp. 5 K = K0 if k is ifninite or K be a finite extension of K0 if [k : Fp] < ∞. 6 OK the ring of integers of K. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 11.
    Notations: Fix a primenumber p and let Qp the field of p-adic numbers. Consider: 1 k be a perfect field of characteristic p. 2 ¯k be a fix algebraic closure. 3 W := W (k) the ring of Witt vectors with coefficients in k 4 K0 = Frac(W ) its field of fractions. It is an unramified extension of Qp. 5 K = K0 if k is ifninite or K be a finite extension of K0 if [k : Fp] < ∞. 6 OK the ring of integers of K. 7 π be a (fixed) uniformizer. So mK = πOK and k = OK /πOK = W /pW . J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 12.
    K3-surfaces Definition A K3-surface overK is a smooth proper surface XK −→ Spec(K) such that 1 q := H1 (XK , OXK ) = 0 and 2 ωXK OXK . Equivalently KX = 0. where ωXK stands for the canonical sheaf and KX its canonical divisor. This definition is independent of the field K, so we can consider this definition for K = C and we get complex algebraic K3-surfaces. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 13.
    Examples: K3-surfaces were namedby Andr´e Weil in honour of three algebraic geometers, Kummer, K¨ahler and Kodaira, and the mountain K2 in Kashmir. Figure: A quartic in P3 K given by x2 y2 + y2 z2 + z2 x2 J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 14.
    Examples Let S bea non-singular sixtic curve in P2 k where k is a field and consider a double cover i.e., a finite generically ´etale morphism, π : X → P2 k which is ramified along S. Then X is a K3 surface. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 15.
    Example Complete intersections: LetX be a smooth surface which is a complete intersection of n hypersurfaces of degree d1, . . . , dn in Pn+2 over a field k. The adjunction formula shows that Ω2 X/k ∼= OX (d1, . . . , dn − n − 3). So a necessary condition for X to be a K3 surface is d1 + . . . + dn = n + 3. The first possibilities are: n = 1 d1 = 4 n = 2 d1 = 2, d2 = 3 n = 3 d1 = d2 = d3 = 2. For a complete intersection M of dimension n one has that Hi (M, OM (m)) = 0 for all m ∈ Z and 1 ≤ i ≤ n − 1. Hence in those three cases we have H1 (X, OX ) = 0 and therefore X is a K3 surface. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 16.
    Example Let A bean abelian surface over a field k of characteristic different from 2. Let A[2] be the kernel of the multiplication by-2-map, let π : ˜A → A be the blow up of A[2] and let ˜E be the exceptional divisor. The automorphism [−1]A lifts to an involution [−1]˜A on ˜A. Let X be the quotient variety of ˜A by the group of automorphisms {id˜A, [−1]˜A} and denote by ι : ˜A → X the quotient morphism. It is a finite map of degree 2. We have the following diagram of morphisms over k. The variety X is a K3 surface and it is called the Kummer surface associated to A. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 17.
    Semistable K3-surfaces Definition XK hassemistable reduction if it has a semi-stable model: XK // X Spec(K) // Spec(OK) that is a proper (flat) model X → Spec(OK) whose special fibre ¯X is smooth over k or ´etale locally a normal crossing divisor. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 18.
    Good reduction If thespecial fibre ¯X → Spec(k) of such a model X is smooth, then we say that XK has good reduction. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 19.
    Layout J. Rogelio P´erezBuend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 20.
    p-adic representations Let GK:= Gal(K, K) be the absolute Galois group of K. Definition A p-adic representation V of GK is a finite dimensional Qp-vector space with a continuous action of GK . J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 21.
    Examples of p-adicrepresentations The main example: Main example The ´etale cohomology of a K3-surface. Indeed, in general we have that if X is a proper and smooth variety over K, then Hi ´et(X¯K , Qp) is a p-adic representation of GK . J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 22.
    Examples of p-adicrepresentations The main example: Main example The ´etale cohomology of a K3-surface. Indeed, in general we have that if X is a proper and smooth variety over K, then Hi ´et(X¯K , Qp) is a p-adic representation of GK . Tate modules of abelian varieties. The r-Tate twists of Qp, Qp(r). J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 23.
    Ring of periods Inorder to study the p-adic representations, Fontaine defines what we know as ring of periods, which are topological Qp-algebras B (or B•), with a continuous linear action of GK and some additional structures which are compatible with the action of GK (for example the monodromy operator N, Frobenius, filtrations). J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 24.
    Poincar´e duality For asmooth and projective variety X of dimension n over the complex numbers C, we have the Betti cohomlogy Hi (X(C), Z). By Poincar´e duality we have that: H2n−i (X, C) Hi (X(C), C). J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 25.
    Complex periods Also wehave a perfect pairing given by the periods: Hi dR(X(C)/C) × H2n−i (X(C), C) −→ C (ω, λ) → λ ω. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 26.
    Comparison isomorphism We havea natural comparison isomorphism: Hi dR(X(C)/C) Hi (X(C), C). We remark that in order to have this isomorphism it is very important to have coefficients in C (for example, this is not an isomorphism over Q). In this sense C is a ring of periods (it contains all the periods λ ω). J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 27.
    The p-adic caseof Cp We denote by Cp = ˆ¯K the p-adic completion of ¯K. We want analogous comparison isomorphisms in the p-adic cases. However the situation is not as easy as in the complex case, mainly because Cp does not have enough periods. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 28.
    Fontaine’s Idea The originalidea of Fontaine was to construct these ring of periods, in order to be able to have analogous comparison isomorphism between the different cohomologies in p-adic settings. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 29.
    B• Examples of thisrings are 1 BHT := q∈Z Cp(q) B Hodge-Tate. is a graded C p-algebra with GK -action rescts gradings and BGK HT = K. 2 BdR : B de Rham is a complete discrete valuation field over K with residue field Cp. It contains K (but not Cp). It has an action of GK and a filtration by its valuation, and its graded quotient gri BdR = Cp(i) J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 30.
    Bcris Bcris: B crysis an algebra over K0 and a GK -stable subring of BdR . It contains K0 but not K. We have a filtration coming from form BdR , a σ-semilinear injective GK -equivariant endomorphism φ (Frobenius endomorphism). BGK cis = K0. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 31.
    Bst Bst: B semistableis an algebra over K0 and has a GK -action. It contains Bcris and KO but not K The Frobenius of Bcris extends to Bst and has a Bcris-derivation N : Bst −→ Bst. Nφ = pφN and BGK st = K0, BN=0 st = Bcris. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 32.
    Dieudonn´e Modules These ringsare such that the BGK -modules DB (V ) := (B ⊗Qp V )GK give us (or expected to give us) good invariants for V . For example comparison isomorphisms for the p-´adic ´etale cohomology and de Rham cohomologie or crystalline cohomology or nice criterion for good reduction of varieties. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 33.
    B-admissible Let L =BGK . Definition A p-adic representation V is B-admissible, if dimL DB (V ) = dimQp V . Definition A p-adic representation V , is crystalline (semistable, Hodge-Tate, semistable) if V is Bcris-admissible (B•-admissible). B-admissibility translates to isomorphisms which are analogous to the comparison isomorphisms in the complex case. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 34.
    Fontaine has definedseveral subcategories of the category of all p-adic representations, denoted by RepGK . This categories are formed by the property of being B-admissible objects. So for any of the period rings B we have a subcategory of the category of p-adic representations denoted by RepB . These categories satisfy proper contention relations as follows: RepBcris ⊂ RepBst ⊂ RepBdR ⊂ RepBHT ⊂ RepGK . J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 35.
    C•-conjectures Let XK bea proper smooth variety over K. CHT : The Hodge-Tate conjecture. There exists a canonical iomorphism, which is compatible with the Galois action. Cp ⊗Qp Hm et (X¯K , Qp) 0≤i≤m Cp(−i) ⊗K Hm−i (X¯K , Ωi XK /K ). J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 36.
    C•-conjectures Let XK bea proper smooth variety over K. CHT : The Hodge-Tate conjecture. There exists a canonical iomorphism, which is compatible with the Galois action. Cp ⊗Qp Hm et (X¯K , Qp) 0≤i≤m Cp(−i) ⊗K Hm−i (X¯K , Ωi XK /K ). CdR : The de Rham conjecture. There exist a conaonical isomorphism, which is compatible with Galois action and filtrations. BdR ⊗Qp Hm et (X¯K , Qp) BdR ⊗K Hm dR (XK /K). J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 37.
    C•-conjectures Ccris: The Crystallineconjecture. Let X be a proper smooth model of XK over OK . Let ¯X be the special fibre of X. There exist a canonical isomorphism which is compatible with the Galois action, and Frobenius endomorphism. Bcris ⊗Qp Hm ´et (X¯K , Qp) Bcris ⊗W Hm crys(¯X/W ) J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 38.
    C•-conjectures Ccris: The Crystallineconjecture. Let X be a proper smooth model of XK over OK . Let ¯X be the special fibre of X. There exist a canonical isomorphism which is compatible with the Galois action, and Frobenius endomorphism. Bcris ⊗Qp Hm ´et (X¯K , Qp) Bcris ⊗W Hm crys(¯X/W ) Barthelo-Ogus isomorphism: K ⊗W Hm crys(¯X/W ) Hm dR (XK /K). J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 39.
    Cst conjecture 1 Cst:The semistable conjecture: Let X be a proper semistable model of XK over OK . Let Y be the special fiber of X, and MY be a naural log-structure on Y . There is a canonical isomorphsim, compatible with Galois action, Frobenius and operator N. Bst ⊗Qp Hm et (XK , Qp) Bst ⊗W Hm log −crys((Y , MY ), (W , O∗ )) J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 40.
    Cst conjecture 1 Cst:The semistable conjecture: Let X be a proper semistable model of XK over OK . Let Y be the special fiber of X, and MY be a naural log-structure on Y . There is a canonical isomorphsim, compatible with Galois action, Frobenius and operator N. Bst ⊗Qp Hm et (XK , Qp) Bst ⊗W Hm log −crys((Y , MY ), (W , O∗ )) 2 Hydo-Kato isomorphism K ⊗W Hm log −crys((Y , MY ), (W , O∗ )) HdR (XK /K) J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 41.
    History For X/K aproper smooth variety over K. Fontaine: Proved that Tate modules V = TpA ⊗Zp Qp of abelian varieties A are de Rham and that DdR(V ) (HdR(X/K))v . J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 42.
    History For X/K aproper smooth variety over K. Fontaine: Proved that Tate modules V = TpA ⊗Zp Qp of abelian varieties A are de Rham and that DdR(V ) (HdR(X/K))v . Fontaine and Messing: Proved the comparison theorem for Hi ´et(X¯K , Qp) for i ≤ p − 1 and K/Qp finite unramified. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 43.
    History For X/K aproper smooth variety over K. Fontaine: Proved that Tate modules V = TpA ⊗Zp Qp of abelian varieties A are de Rham and that DdR(V ) (HdR(X/K))v . Fontaine and Messing: Proved the comparison theorem for Hi ´et(X¯K , Qp) for i ≤ p − 1 and K/Qp finite unramified. Kato, Hydo Tsuji: Extended these results to finally prove that one can recover Hi dR(X/K) from the data of V = Hi ´et(X¯K , Qp) as a p-adic representation. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 44.
    History For X/K aproper smooth variety over K. Fontaine: Proved that Tate modules V = TpA ⊗Zp Qp of abelian varieties A are de Rham and that DdR(V ) (HdR(X/K))v . Fontaine and Messing: Proved the comparison theorem for Hi ´et(X¯K , Qp) for i ≤ p − 1 and K/Qp finite unramified. Kato, Hydo Tsuji: Extended these results to finally prove that one can recover Hi dR(X/K) from the data of V = Hi ´et(X¯K , Qp) as a p-adic representation. Tsuji, Niziol, Faltings: Proved that if X is semistable, then V is Bst -admissible and that V is crystalline if V has good reduction and BdR otherwise. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 45.
    For abelian varieties ForAbelian varieties, Bcris and Bst are exactly what it takes to decide: whether A has good reduction or semistable reduction. Crystalline criterion for abelian varieties: Coleman-Iovita Breuil: A has good reduction if and only if V is crystalline. A has semistable reduction if and only if V is semistable. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 46.
    My Thesis problem Crystallinecriterion for K3 surfacess: Let X be a K3 surface over a p-adic field K with semistable reduction. X has good reduction (¯X → Spec(k) is smooth) if and only if V := H2 ´et(X¯K , Qp) is Crystalline (Bcris-admissible). J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 47.
    One side isFalting’s result: Remember that RepBcris ⊂ RepBst Since X has semistable reduction, then V is Bst-admissible. If X has good reduction, then by Falting’s result, V is Bcris-admissible. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 48.
    Results of Y.Matsumoto Theorem Let K be a local field with residue characteristic p = 2 and X a Kummer surface over K. Assume that X has at least one K-rational point. If H2 et(X¯K , Qp) is crystalline, then XK has good reduction for some finite unramified extension K /K. Theorem Let K be a local field with residue characteristic p = 2, 3, and Y a K3 surface over K with Shioda-Inose structure of product type. If H2 et(YK , Qp) is crystalline, then YK has good reduction for some finite extension K /K of ramification index 1, 2, 3, 4 or 6. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 49.
    Main tool The maintooll is what we call p-adic logarithmic degenerations of a K3-surface. These will be p-adic analogous of degeneration of K3 surfaces over the complex numbers constructed via degenerations. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 50.
    Complex degenerations ofK3-surfaces Definition Over the complex numbers C, a semistable degeneration of a K3-surface X is a proper flat and surjective morphism π : X(C) → ∆ over the open disc, whose general fibre Xt = π−1 (t), for t = 0 is a smooth K3-surface and X0 is reduced with normal crossings. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 51.
    Modification of adegeneration Definition A modification of π : X(C) → ∆ is a degeneration of surfaces π : X(C) → ∆ such that there exists a birational map φ : X(C) → X (C) given an isomorphism form (X(C) − X0) −→ (X (C) − X0) and such that the diagram: X(C) φ // π X (C) π || ∆ commutes. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 52.
    Kulikov degenerations We havethe following theorem: Theorem (Kulikov, Persson, Pinkham) Let π : X(C) → ∆ be a semistable degeneration of a K3-surface, then there exists a modification π : X (C) → ∆ such that the canonical divisor of the total space X (C) is trivial. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 53.
    Kulikov degenerations We havethe following theorem: Theorem (Kulikov, Persson, Pinkham) Let π : X(C) → ∆ be a semistable degeneration of a K3-surface, then there exists a modification π : X (C) → ∆ such that the canonical divisor of the total space X (C) is trivial. A degeneration with trivial canonical divisor is called a good degeneration or a Kulikov degeneration. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 54.
    Kulikov criterion Theorem Let X(C)→ ∆ be a good degeneration of a K3-surface. The degenerate fibre X0 is one of the following three types: I. X0 is a nonsingular K3 surface. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 55.
    Kulikov criterion Theorem Let X(C)→ ∆ be a good degeneration of a K3-surface. The degenerate fibre X0 is one of the following three types: I. X0 is a nonsingular K3 surface. II. X0 = ∪n i=1Vi where the Vi are rational surfaces and V2, . . . , Vn−1 are elliptic ruled surfaces. III. X0 = ∪n i=1Vi where all the Vi are rational surfaces. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 56.
    In therms ofmonodromy Moreover, the three cases can be distinguished from each other by means of the monodromy T acting on H2 (Xt, Z): For Type I we have N := ln T = 0 that is T = id. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 57.
    In therms ofmonodromy Moreover, the three cases can be distinguished from each other by means of the monodromy T acting on H2 (Xt, Z): For Type I we have N := ln T = 0 that is T = id. For Type II, N = 0 but N2 = 0. For Type III, N2 = 0 but N3 = 0 J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 58.
    Layout J. Rogelio P´erezBuend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 59.
    The plan: We need: Ap-adic semistable degeneration of our K3-surface. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 60.
    The plan: We need: Ap-adic semistable degeneration of our K3-surface. A monodromy operator N on the log-crystalline cohomology. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 61.
    The plan: We need: Ap-adic semistable degeneration of our K3-surface. A monodromy operator N on the log-crystalline cohomology. We relate it with the monodromy operator on Dst(H2 et(X¯K , Qp)) H2 log−cris(XK /W ) appearing on Fontain’s theory. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 62.
    The plan: We need: Ap-adic semistable degeneration of our K3-surface. A monodromy operator N on the log-crystalline cohomology. We relate it with the monodromy operator on Dst(H2 et(X¯K , Qp)) H2 log−cris(XK /W ) appearing on Fontain’s theory. By p-adic Hodge theory if H2 ´et(X¯K , Qp) is crystalline then N = 0. Indeed BN=0 st = Bcris and Dst(V )N=0 = Dcris(V ) , so if a p-adic representation is crystalline we most have N = 0. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 63.
    Finally we basechange to the complex numbers and use Kulikov’s classification theorem to deduce that our crystalline K3-surface has good reduction. Here we use the Deligne’s work on the Monodromy expressed as the residue at zero of the GM-conexion. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 64.
    Layout J. Rogelio P´erezBuend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 65.
    Logarithmic geometry isconcerned with a method of finding and using“hide smoothness”in singular varieties. Let X be a nonsingular irreducible complex variety, S a smooth curve with a point s and f : X → S a dominant morphism smooth away from s, the fiber Xs := f −1 (s) = Y1 ∪ · · · ∪ Yn reduced simple normal crossing divisor. ΩX/S = ΩX /f ∗ ΩS fails to be locally free at the singular points of f . J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 66.
    Consider ΩX/S (log(Xs))the sheaf of differentials with at most logarithmic poles along the Yi , and similarly ΩS (log(s)), there is an injective sheaf homomorphism f ∗ ΩX (log(Xs)) −→ ΩS (log(s)) and the quotient sheaf ΩX (log(XS ))/f ∗ ΩX (log(Xs)) is locally free. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 67.
    pre-log.st Definition 1 Let Xbe a scheme. A pre-log structure on X, is a sheaf of monoids MX together with a morphism of sheaves of monoids: α : MX −→ OX , called the structure morphism. 2 A pre-log structure is called a log structure (log.st for short) if α−1 (O∗ X ) O∗ X via α. 3 The pair (X, MX ) is called a log scheme and it will be denoted by X× . 4 Morphisms are morphisms of sheaves which are compatible with the structure morphism. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 68.
    Induced log.st We havethe forgetful functor i from the category of log.st of X to the category of pre-log.st of X by sending a log.st M in X to itself considered as a pre-log.st i(M). Vice-versa given a pre-log.st we can construct a log.st Mls out of it in such a way that ( )ls is left adjoint of i, hence Mls is universal. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 69.
    Inverse image log.st Definition Letf : X → Y be a morphism of schemes. Given a log.st MY on Y we can define a log.st on X, called the inverse image of MY , to be the log structure associated to the pre-log.st f −1 (MY ) → f −1 (OY ) → OX . This is denoted by f ∗ (MY ). J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 70.
    Morphisms of log-schemes Definition Bya morphism of log-schemes X∗ −→ Y ∗ we understand a morphism of the underlying schemes f : X → Y and a morphism f # : f ∗ MY → MX of log.st on X. We denote by LSch the category of log.schemes. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 71.
    One of themain examples of interest for us is the following: Example Let X be a regular scheme (we can take for example a K3-surface over K or a proper model of it). Let D be a divisor of X. We can define a log.st M on X associated to the divisor D as M(U) := g ∈ OX (U) : g|UD ∈ O∗ X (U D) J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 72.
    log.st to algebraizableformal schemes Let X be a scheme and ˆX is a formal completion of X along a closed subscheme Y , then we have a morphism of ringed spaces: ˆX φ −→ X for which φ is the inclusion Y → X on topological spaces, and on sheaves, it is the natural projection OX −→ lim ←− OX /In = OˆX where I is the sheaf of ideals defined by the closed immersion Y → X. If we have a log.st on X, say M, we can give a log structure on ˆX by taking the inverse image of the log structure M so that ˆX becomes a log-formal scheme: (ˆX, φ∗ M). J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 73.
    For K3-surfaces 1 WhenX is a proper model of a K3-surface XK , we have that the special fibre ¯X of X is a closed divisor with normal crossings. This divisor induces a log.st on X. We denote by X× the log-formal scheme obtained as in the previews paragraph; that is, by completing X along ¯X and giving to it the inverse image log.st of X induced by ¯X. 2 Notice that we have an inclusion of ringed spaces ¯X → X× . We denote by ¯X× the log-scheme obtained by giving to ¯X the inverse image log.st of X× . J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 74.
    Layout J. Rogelio P´erezBuend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 75.
    p-adic degeneration Definition A p-adicdegeneration of a K3-surface with semistalbe reduction is a proper, flat morphism of schemes X −→ Spec(W[[t]]) with geometrically connected fibres, such that: 1 We have an isomorphism of the semistable model X of XK with the fibre Xπ of X → Spec(W[[t]]) induced by the ring homomorphism: W [[t]] → OK ; t −→ π. 2 We have an isomorphism (compatible with the previous one) of the special fibre ¯X of the semistable model of XK with the fibre X0 induced by the projection W [[t]] → W [[t]]/(p, t) k = OK /πOk . 3 X → Spec(W[[t]]) is smooth in the complement of ¯X that is (X − ¯X) −→ (Spec(W[[t]]) − Spec(k)) is smooth. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 76.
    In a diagram Thenwe have commutative Cartesian diagrams: ¯X // X // X Spec(k) // Spec(OK) // Spec(W[[t]]) . Note that Spec(W[[t]]) is the analogous, in p-adic settings, of the open unit disc ∆ in the complex numbers, and so we call Spec(W[[t]]) the p-adic unit disc denoted by D. Then X is a family of surfaces parametrized by the p-adic unit disc D and removing the special fibre ¯X smooth over D∗ = D − Spec(k). J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 77.
    rig functor 1 LetY be the fibre of f at t = 0, that is the fibre induced by the morphism W [[t]] → W ; t → 0. This is a scheme over Spec(W) whose special fibre is again X. Moreover Y is a normal crossing divisor (but now in characteristic zero). 2 Call X = (X× )rig, D = (D× )rig, and f = (f × )rig the rigid analytic spaces over K0. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 78.
    rigid version ofthe degeneration Lemma Under the previous settings we have: 1 X −→ Spec(K0) is smooth 2 Y := f −1 (0) = (Y× )rig is a semistable surface over K0. 3 f |X∗ : X∗ := (X − Y) −→ D∗ := (D − {0}) is smooth. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 79.
    Layout J. Rogelio P´erezBuend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 80.
    Complex of relativelogarithmic differentials Consider the complex of sheaves K· X/D induced by the relative logarithmic differential: OX d1 X/D −−−→ OX ⊗X/K0 Ω1 X/D(log(Y)) d2 X/D −−−→ OX ⊗X/K0 Ω2 X/D(log(Y)) J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 81.
    The connection Denote byHi the i-th logarithmic relative de Rham cohomology group of X/D with coefficients in OX , i.e, it is the sheaf Rf∗(K· X/D). For every i, Hi is a free OD-module with an integrable, regular-singular connection i : Hi −→ Hi ⊗OD Ω1 D/K0 (log(0)). J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 82.
    Monodromy If s isa point in D, let Hi s be the fibre of H1 at s. We now define the monodromy Ni as the residue at 0 of this connection. That is Ni = res0( i ). In our case the only important value is for i = 2, so we define the monodromy as N := N2. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
  • 83.
    Bibliography Andreatta, F., andA. Iovita. 2012. Semistable Sheaves and Comparison Isomorphisms in the Semistable Case. Berthelot, P. 1986. G´eom´etrie Rigide Et Cohomologie Des Vari´et´es Alg´ebriques De Caract´eristique P. Bull. Soc. Math. France. Coleman, R., and A. Iovita. 2003. Hidden Structures on Semi-Stable Curves. Preprint. Faltings, G. 1988. P-Adic Hodge Theory. J. Amer. Math. Soc. Faltings, G. 1992. Crystalline Cohomology of Semistable Curves, and P-Adic Galois-Representations. Journal of Algebraic Geometry 1, no. 1: 61–81. Huybrechts, D. Lectures on K3-Surfaces. Unpublished Notes Available on the Author’s Website at the University of Bonn. Kato, F. 1996. Log Smooth Deformation Theory. Tohoku Mathematical Journal. Kato, K. 1989. Logarithmic Structures of Fontaine-Illusie. Algebraic Analysis. Kawamata, Y., and Y. Namikawa. 1994. Logarithmic Deformations of Normal Crossing Varieties and Smoothing of Degenerate Calabi-Yau Varieties. Inventiones Mathematicae 118, no. 1 (December): 395–409. http://imperium.lenin.ru/ kaledin/math/pdf/kawa-naka.pdf. Kulikov, V.S. 2007. Degenerations of K3 Surfaces and Enriques Surfaces. Mathematics of the USSR-Izvestiya. MORRISON, D.R. 2012. The Geometry of K3 Surfaces. Cgtp.Duke.Edu. Accessed October 13. http://www.cgtp.duke.edu/ITP99/morrison/cortona.pdf. 223. J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a
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    Bibliography Olsson, M.C. 2004.Semistable Degenerations and Period Spaces for Polarized K3 Surfaces. Duke Mathematical Journal 125, no. 1: 121–203. Rizov, J. 2010. Kuga-Satake Abelian Varieties of K3 Surfaces in Mixed Characteristic. Journal F¨Ur Die Reine Und Angewandte Mathematik 648: 13–67. Schroeer, S. 2000. Logarithmic Deformations of Normal Crossing Enriques Surfaces in Characteristic Two. arXiv.org (May 8). Siegfreid, B. 2012. Formal and Rigid Geometry. Ed. Werner lurkebohemart. People.Math.Jussieu.Fr. Accessed August 30. http://people.math.jussieu.fr/ fmartin/these/G Berger, L. 2004. An Introduction to the Theory of P-Adic Representations. Geometric Aspects of Dwork Theory 1: 255–292. BRINON, O., and B. CONRAD. 2008. CMI SUMMER SCHOOL NOTES on P-ADIC HODGE THEORY (PRELIMINARY VERSION) . arXiv.org. Colmez, P. 1998. Repr´esentations P-Adiques D’un Corps Local. Proceedings of the International Congress of . . . . Fontaine, J.M. 1982. Sur Certains Types De Representations P-Adiques Du Groupe De Galois D’Un Corps Local; Construction D”Un Anneau De Barsotti-Tate. The Annals of Mathematics 115, no. 3: 529–577. Serre, J.P., and M.J. Greenberg. 1979. Local Fields 191. Fontaine, J.M. 1994. Periodes p-adiques (S´eminaire de Bures, 1988). SMF - Publications - Ast´erisque - Titles - 1994 - J. Rogelio P´erez Buend´ıa A Crystalline Criterion for Good Reduction on Semi-stable K3-Surfaces over a