2,630 reputation
1628
bio website jakitoimgeisterhaus.blogspot.…
location Munich, Germany
age 37
visits member for 2 years, 10 months
seen 2 hours ago

My past research interests included differential algebraic equations, nonlinear analysis and relations between symmetries and structural properties.

I recently investigated hierarchical structures, starting from group cohomology, continuing with semi-group theory and ending with lattices and universal algebra.


13h
accepted Which constructions on a category are still interesting for a groupoid?
Mar
12
accepted Are these adjoint functors to/from the category of monoids with semigroup homomorphisms?
Feb
3
accepted Which of these constructions are left adjoints?
Jan
22
accepted Relation between concept lattice and Dedekind–MacNeille completion
Aug
23
accepted Existence of maximal boolean-algebra sublattice (preserving top and bottom) of finite distributive lattice
Jun
9
accepted How to express the powers of two by a Diophantine equation?
Jun
7
accepted Which set theories without the power set axiom are used occasionally?
May
5
accepted Why is quantified propositional logic not part of first-order logic?
May
4
accepted Monadic second order logic without constants, functions and equality
May
4
accepted Paradox: Any set theory without universe set is not a model of itself
Apr
6
accepted Are there simple models of Euclid's postulates that violate Pasch's theorem or Pasch's axiom?
Mar
15
accepted Are Horn clauses always universally quantified?
Jan
3
accepted Can second order logic express each (computable) infinitary logic sentence?
Dec
20
accepted Polynomial bounded real part of an entire function
Nov
2
accepted Relation between lattice theory and semilattice theory
Oct
29
accepted Orders on the Cartesian product of partially ordered sets
Oct
27
accepted What is the smallest variety of algebras containing all fields?
Oct
25
accepted Is the set of all definable subsets of the natural numbers recursively enumerable?
Jul
9
accepted Weak categoricity in first order logic
Apr
14
accepted What is the “common” definition of model in first order logic?