## Table of contents

- Differentiability theory for distributions and subsets of Euclidean space
- Survey on varifolds suitable for beginning graduate students
- Partial differential equations on singular surfaces with mean curvature – foundations
- Regularity of singular surfaces with mean curvature
- Basic geometric properties of singular surfaces with mean curvature
- Conference proceedings
- List of minor corrections

This page was last modified on: 20 August 2020, 06:06, CST

## Differentiability theory for distributions and subsets of Euclidean space

U. Menne

[14] *Pointwise differentiability of higher order for
distributions*, 33 pages.

Anal. PDE, accepted, 2019.

ArXiv: 1803.10855v2 [math.FA].

**Abstract:** For distributions, we build a
theory of higher order pointwise differentiability comprising,
for order zero, Łojasiewicz's notion of point value.
Results include Borel regularity of differentials, higher
order rectifiability of the associated jets, a
Rademacher-Stepanov type differentiability theorem, and a
Lusin type approximation. A substantial part of this
development is new also for zeroth order. Moreover, we
establish a Poincaré inequality involving the natural
norms of negative order of differentiability. As a corollary,
we characterise pointwise differentiability in terms of point
values of distributional partial derivatives.

U. Menne, M. Santilli

[11] * A geometric second-order-rectifiable stratification
for closed subsets of Euclidean space*, 14 pages.

Ann. Sc. Norm. Super. Pisa Cl. Sci. (5), 19(3):1185-1198,
2019.

DOI: 10.2422/2036-2145.201703_021. ArXiv: 1703.09561v2 [math.CA].

**Abstract:** Defining the *m*-th stratum of
a closed subset of an *n* dimensional Euclidean space to
consist of those points, where it can be touched by a ball
from at least *n−m* linearly independent directions, we
establish that the *m*-th stratum is second-order
rectifiable of dimension *m* and a Borel set. This was
known for convex sets, but is new even for sets of positive
reach. The result is based on a sufficient condition of
parametric type for second-order rectifiability.

U. Menne

[9] *Pointwise differentiability of higher order for
sets*, 31 pages.

Ann. Global Anal. Geom., 55(3), 591–621, 2019.

Springer Nature SharedIt: https://rdcu.be/bgUqa

DOI: 10.1007/s10455-018-9642-0. ArXiv: 1603.08587v2 [math.DG].

**Abstract:** The present paper develops two
concepts of pointwise differentiability of higher order for
arbitrary subsets of Euclidean space defined by comparing
their distance functions to those of smooth submanifolds.
Results include that differentials are Borel functions, higher
order rectifiability of the set of differentiability points,
and a Rademacher result. One concept is characterised by a
limit procedure involving inhomogeneously dilated sets. The
original motivation to formulate the concepts stems from
studying the support of stationary integral varifolds. In
particular, strong pointwise differentiability of every
positive integer order is shown at almost all points of the
intersection of the support with a given plane.

## Survey on varifolds suitable for beginning graduate students

U. Menne

[12] *The concept of varifold*, 5 pages.

Notices Amer. Math. Soc., 64(10):1148–1152, 2017.

DOI: 10.1090/noti1589. ArXiv: 1705.05253v4 [math.DG].

**Abstract:** We survey – by means of 20 examples
– the concept of varifold, as generalised submanifold, with
emphasis on regularity of integral varifolds with mean
curvature, while keeping prerequisites to a minimum. Integral
varifolds are the natural language for studying the
variational theory of the area integrand if one considers, for
instance, existence or regularity of stationary (or, stable)
surfaces of dimension at least three, or the limiting
behaviour of sequences of smooth submanifolds under area and
mean curvature bounds.

## Partial differential equations on singular surfaces with mean curvature – foundations

U. Menne

[8] *Sobolev functions on varifolds*, **50
pages**.

Proc. Lond. Math. Soc. (3), 113(6):725–774, 2016.

Wiley Content Sharing: https://rdcu.be/bV3Rw

DOI: 10.1112/plms/pdw023. ArXiv: 1509.01178v3 [math.CA].

**Abstract:** This paper introduces first-order
Sobolev spaces on certain rectifiable varifolds. These
complete locally convex spaces are contained in the generally
non-linear class of generalised weakly differentiable
functions and share key functional analytic properties with
their Euclidean counterparts.

Assuming the varifold to satisfy a uniform lower density bound
and a dimensionally critical summability condition on its mean
curvature, the following statements hold. Firstly, continuous
and compact embeddings of Sobolev spaces into Lebesgue spaces
and spaces of continuous functions are available. Secondly,
the geodesic distance associated to the varifold is a
continuous, not necessarily Hölder continuous Sobolev function
with bounded derivative. Thirdly, if the varifold additionally
has bounded mean curvature and finite measure, then the
present Sobolev spaces are isomorphic to those previously
available for finite Radon measures yielding many new results
for those classes as well.

Suitable versions of the embedding results obtained for
Sobolev functions hold in the larger class of generalised
weakly differentiable functions.

U. Menne

[6] *Weakly differentiable functions on varifolds*
**112 pages**.

Indiana Univ. Math. J., 65(3):977–1088, 2016.

DOI: 10.1512/iumj.2016.65.5829. ArXiv: 1411.3287v1 [math.DG].

**Abstract:** The present paper is intended to
provide the basis for the study of weakly differentiable
functions on rectifiable varifolds with locally bounded first
variation. The concept proposed here is defined by means of
integration-by-parts identities for certain compositions with
smooth functions. In this class, the idea of zero boundary
values is realised using the relative perimeter of superlevel
sets. Results include a variety of Sobolev Poincaré-type
embeddings, embeddings into spaces of continuous and sometimes
Hölder-continuous functions, and pointwise differentiability
results both of approximate and integral type as well as
coarea formulae.

As a prerequisite for this study, decomposition properties of
such varifolds and a relative isoperimetric inequality are
established. Both involve a concept of distributional boundary
of a set introduced for this purpose.

As applications, the finiteness of the geodesic distance
associated with varifolds with suitable summability of the
mean curvature and a characterisation of curvature varifolds
are obtained.

## Regularity of singular surfaces with mean curvature

S. Kolasiński, U. Menne

[7] *Decay rates for the quadratic and super-quadratic
tilt-excess of integral varifolds*, **56
pages**.

NoDEA Nonlinear Differential Equations Appl., 24:Art. 17, 56,
2017.

DOI: 10.1007/s00030-017-0436-z. ArXiv: 1501.07037v2 [math.DG].

**Abstract:** This paper concerns integral
varifolds of arbitrary dimension in an open subset of
Euclidean space satisfying integrability conditions on their
first variation. Firstly, the study of pointwise power decay
rates almost everywhere of the quadratic tilt-excess is
completed by establishing the precise decay rate for
two-dimensional integral varifolds of locally bounded first
variation. In order to obtain the exact decay rate, a coercive
estimate involving a height-excess quantity measured in Orlicz
spaces is established. Moreover, counter-examples to pointwise
power decay rates almost everywhere of the super-quadratic
tilt-excess are obtained. These examples are optimal in terms
of the dimension of the varifold and the exponent of the
integrability condition in most cases, for example if the
varifold is not two-dimensional. These examples also
demonstrate that within the scale of Lebesgue spaces no local
higher integrability of the second fundamental form, of an at
least two-dimensional curvature varifold, may be deduced from
boundedness of its generalised mean curvature vector. Amongst
the tools are Cartesian products of curvature varifolds.

U. Menne

[4] *Second order rectifiability of integral varifolds of
locally bounded first variation*, **55
pages**.

J. Geom. Anal., 23(2):709–763, 2013.

DOI: 10.1007/s12220-011-9261-5. ArXiv: 0808.3665v3 [math.DG].

**Abstract:** It is shown that every integral
varifold in an open subset of Euclidean space whose first
variation with respect to area is representable by integration
can be covered by a countable collection of submanifolds of
the same dimension of class 2 and that their mean curvature
agrees almost everywhere with the variationally defined
generalized mean curvature of the varifold.

U. Menne

[3] *Decay estimates for the quadratic tilt-excess of
integral varifolds*, **83 pages**.

Arch. Ration. Mech. Anal., 204(1):1–83, 2012.

DOI: 10.1007/s00205-011-0468-1. ArXiv: 0909.3253v3 [math.DG].

**Abstract:** This paper concerns integral
varifolds of arbitrary dimension in an open subset of
Euclidean space with their first variation given by either a
Radon measure or a function in some Lebesgue space. Pointwise
decay results for the quadratic tilt-excess are established
for those varifolds. The results are optimal in terms of the
dimension of the varifold and the exponent of the Lebesgue
space in most cases, for example if the varifold is not
two-dimensional.

## Basic geometric properties of singular surfaces with mean curvature

U. Menne, C. Scharrer

[13] *A novel type of Sobolev-Poincaré inequality for
submanifolds of Euclidean space*, 35 pages.

In revision (to include one or more applications), 2017.

ArXiv: 1709.05504v1 [math.DG].

**Abstract:** For functions on generalised
connected surfaces (of any dimensions) with boundary and mean
curvature, we establish an oscillation estimate in which the
mean curvature enters in a novel way. As application we prove
an a priori estimate of the geodesic diameter of compact
connected smooth immersions in terms of their boundary data
and mean curvature. These results are developed in the
framework of varifolds. For this purpose, we establish that
the notion of indecomposability is the appropriate substitute
for connectedness and that it has a strong regularising
effect; we thus obtain a new natural class of varifolds to
study. Finally, our development leads to a variety of
questions that are of substance both in the smooth and the
nonsmooth setting.

U. Menne, C. Scharrer

[10] *An isoperimetric inequality for diffused surfaces*,
16 pages.

Kodai Math. J., 41(1):70–85, 2018.

DOI: 10.2996/kmj/1521424824. ArXiv: 1612.03823v2 [math.DG].

**Abstract:** For general varifolds in Euclidean
space, we prove an isoperimetric inequality, adapt the basic
theory of generalised weakly differentiable functions, and
obtain several Sobolev type inequalities. We thereby intend to
facilitate the use of varifold theory in the study of diffused
surfaces.

U. Menne

[2] *A Sobolev Poincaré type inequality for integral
varifolds*, 40 pages.

Calc. Var. Partial Differential Equations, 38(3-4):369–408,
2010.

DOI: 10.1007/s00526-009-0291-9. ArXiv: 0808.3660v2 [math.DG].

**Abstract:** In this work a local inequality is
provided which bounds the distance of an integral varifold
from a multivalued plane (height) by its tilt and mean
curvature. The bounds obtained for the exponents of the
Lebesgue spaces involved are shown to be sharp.

U. Menne

[1] *Some applications of the isoperimetric inequality for
integral varifolds*, 23 pages.

Adv. Calc. Var., 2(3):247–269, 2009.

DOI: 10.1515/ACV.2009.010. ArXiv: 0808.3652v1 [math.DG].

**Abstract: **In this work the isoperimetric
inequality for integral varifolds of locally bounded first
variation is used to obtain sharp estimates for the size of
the set where the density quotient is small and to generalise
Calderón's and Zygmund's theory of first order
differentiability for functions in Lebesgue spaces from
Lebesgue measure to integral varifolds.

## Conference proceedings

U. Menne

[5] *A sharp lower bound on the mean curvature integral with
critical power for integral varifolds*, 3 pages.

In abstracts from the workshop held July 22-28, 2012,
Organized by Camillo De Lellis, Gerhard Huisken and Robert
Jerrard, Oberwolfach Reports. Vol. 9, no. 3, 2012.

DOI: 10.4171/OWR/2012/36.