Sefi Ladkani
During the years 20112014
I held a temporary position as a principal investigator
at the
Mathematical Institute
of the University of Bonn
within the framework of Priority Program
SPP 1388 (Representation Theory) of the
DFG (German Research Foundation).
Prior to that, I spent two years as a postdoctoral researcher at the
MaxPlanckInstitute for
Mathematics in Bonn, Germany and one year at the
Institut des Hautes Études
Scientifiques at BuressurYvette, France.
Part of my stay at these institutes was as an
EPDI
(European Postdoctoral Institute) Laureate.
I completed my Ph.D. studies in Mathematics at
The Hebrew University of Jerusalem.
My advisor was
David Kazhdan.
Research
My research interests are in the areas of representation theory and
homological algebra, with a focus on derived categories arising from
combinatorial data.
More specifically, I am interested in:
 Derived and triangulated categories.
 Representations of quivers and finite dimensional algebras.
 Tilting theory.
 Cluster categories.
 Categorification.
 Algebraic aspects of finite partially ordered sets and directed
graphs.
 Sheaves on topological spaces, diagram categories, model
categories.
Recent results
Some short notes, extended abstracts etc. of results announced at various
meetings, arranged in reverse chronological order.

On symmetric Jacobian algebras
(pdf),
abstract of a scheduled talk at the conference
Advances in Representation
Theory of Algebras (ARTA) 2013, Torun, September 2013, claiming
in particular that the
Jacobian algebras of the quivers with potentials arising from
triangulations of closed surfaces are tame symmetric with periodic
modules.
A manuscript presenting the theory in a more general framework is in
preparation.

Derived equivalence classification of the gentle algebras arising
from surface triangulations
(pdf),
talks at the
Representation
theory seminar, Bielefeld, July 2011 and at the
Representation Theory Days, Hannover, November 2011.

On fractionally CalabiYau algebras, coming soon,
talks at the BIRS Workshop
Test
problems for the theory of finite dimensional algebras, Banff,
September 2010,
and at the workshop
Projective
Dimension 2, Bielefeld, October 2010.

with XiaoWu Chen,
The Finflation category and its stable category,
coming soon.
Publications
Arranged according to alphabetical order of the titles.

Algebras of
quasiquaternion type
(pdf)

2CYtilted algebras
that are not Jacobian
(pdf)

Bounds on the global
dimension of certain piecewise hereditary categories,
J. Pure Appl. Algebra 212 (2008), no. 9, 21402145.
(doi,
pdf)

Categorification of a
linear algebra identity and factorization of Serre functors
(pdf)

with Janine
Bastian and
Thorsten Holm,
Derived equivalence
classification of clustertilted algebras of Dynkin type E
Algebr. Represent. Theory. 16 (2013), no. 2, 527551.
(doi,
pdf)
Supplementary material to this paper, including complete lists of the
derived equivalence classes, can be found
here.

Derived
equivalences of triangular matrix rings arising from extensions of
tilting modules,
Algebr. Represent. Theory 14 (2011),
no. 1, 5774.
(doi,
pdf)

Hochschild cohomology
of gentle algebras
(pdf)

Hochschild cohomology
of the clustertilted algebras of finite representation type
(pdf)

Mutation classes of
certain quivers with potentials as derived equivalence classes
(pdf)

On cluster algebras
from once punctured closed surfaces
(pdf)

On derived
equivalences of categories of sheaves over finite posets,
J. Pure Appl. Algebra 212 (2008), no. 2, 435451.
(doi,
pdf)

On derived equivalences
of lines, rectangles and triangles
J. London Math. Soc. 87 (2013), no. 1, 157176.
(doi,
pdf)

On Jacobian algebras
from closed surfaces
(pdf)

On the periodicity
of Coxeter transformations and the nonnegativity of their Euler
forms,
Linear Algebra Appl. 428 (2008), no. 4, 742753.
(doi,
pdf)

Perverse equivalences,
BBtilting, mutations and applications
(pdf)

with Janine
Bastian and
Thorsten Holm,
Towards derived
equivalence classification of the clustertilted algebras of Dynkin
type D
J. Algebra 410 (2014), 277332.
(doi,
pdf)

Universal derived
equivalences of posets
(pdf)

Universal derived
equivalences of posets of cluster tilting objects
(pdf)

Universal derived
equivalences of posets of tilting modules
(pdf)

Which canonical algebras
are derived equivalent to incidence algebras of posets?,
Comm. Algebra 36 (2008), no. 12, 45994606.
(doi,
pdf)

Which mutation classes
of quivers have constant number of arrows?
(pdf)
Ph.D. Thesis:
Homological properties of finite partially ordered sets
(pdf).
M.Sc. Thesis:
On nilpotency problems in metabelian extensions of local fields
(dvi ,
ps)
Presentations
Here are slides of some of my talks.

On Jacobian algebras from closed surfaces,
presentation at
ICRA 2012,
Bielefeld, August 2012
(pdf)

Mutation classes of quivers with constant number of arrows and
derived equivalences,
talk at the BIRS Workshop
Linking
representation theory, singularity theory and noncommutative
algebraic geometry, Banff, May 2012.
A video recording of the talk is available
here.

Mutation classes of quivers with constant number of arrows and
derived equivalences,
presentation at the Conference
of the DFG priority program 1388 "Representation
Theory",
Thurnau, March 2012 (pdf)

Mutation classes of quivers with constant number of arrows and
derived equivalences, slides accompanying my talk at the
Workshop
on Cluster Algebras and Combinatorics 2012, Graz, March 2012,
as well as my talks at Hannover,
Münster, Israel and Paris, from November 2011 to March 2012
(pdf)

Perverse Morita equivalences are everywhere,
presentation at
ICRA XIV,
Tokyo, Japan, August 2010
(pdf)

Combinatorial aspects of derived equivalence,
presentation at the
Darstellungstheorie Schwerpunkttagung,
Bad Honnef, April 2010
(pdf)

On derived equivalences of simplices, prisms and boxes,
slides accompanying my talk at the
Conference
on Homological and Geometrical Methods in Representation Theory,
ICTP, Trieste, February 2010
(pdf)

On derived equivalences of triangles, rectangles and lines,
presentation at the
Workshop on Triangulated Categories and Singularities,
Paderborn, May 2009
(pdf)

On derived equivalences of triangles, rectangles and lines,
presentation at the
Workshop on Representations and Cohomology, Cologne, March 2009
(pdf)

Universal derived equivalences of posets and applications to
clustertilting objects,
poster for the
12th Midrasha Mathematicae on Higher Teichmuller Theory,
Clusters and Quantization, Jerusalem, May 2008
(pdf)

Generalized reflections and derived equivalences of posets,
presentation at the
Conference on Representations of Algebras, Groups and Semigroups,
BarIlan University, January 2008
(pdf)

Posets, sheaves, and their derived equivalences,
presentation at
ICRA XII,
Torun, Poland, August 2007
(pdf)

Piecewise hereditary algebras and posets,
presentation at
ICRA XII,
Torun, Poland, August 2007
(pdf)

Constructions of derived equivalences of finite posets,
presentation at the
Workshop on Triangulated Categories,
Leeds, UK, August 2006
(pdf)

Derived equivalences of categories of sheaves over finite
partially ordered sets, HUJI, May 2006
(pdf)
Teaching
During my Ph.D. studies I have been a teaching assistant at the
Einstein Institute
of Mathematics in the Hebrew University.
Here is the list of the courses I taught.