The paper attempts a systematic study of homomorphisms of relational structures. Such structures are modeled as multialgebras (i.e., relation is represented as a set-valued function). The rst, main, result is that, under reasonable restrictions on the form of the deenition of homomorphism, there are exactly nine compositional homomorphisms of multialgebras. Then the comparison of the obtained c...

Key-homomorphic properties of cryptographic objects have proven to be useful, both from a theoretical as well as a practical perspective. Important cryptographic objects such as pseudorandom functions or (public key) encryption have been studied previously with respect to key-homomorphisms. Interestingly, however, signature schemes have not been explicitly investigated in this context so far. W...

We construct quasi-isometric embeddings from right-angled Artin groups into the outer automorphism group of a free group. These homomorphisms are modeled on the homomorphisms into the mapping class group constructed by Clay, Leininger, and Mangahas in [CLM12]. Toward this goal, we develop tools in the free group setting that mirror those for surface groups and discuss various analogs of subsurf...

We construct a new family of homomorphisms between (graded) Specht modules of the quiver Hecke algebras of type A. These maps have many similarities with the homomorphisms constructed by Carter and Payne in the special case of the symmetric groups, although the maps that we obtain are both more and less general than these.

Following the last talk on graph homomorphisms, we continue to discuss some examples of graph homomorphisms. But this time we will focus on some models, that is, the homomorphism G → H for the graph H with fixed weights. The main reference is Section 1 in [2].

Skeletons model partial information about regular (honest) behavior in an execution of a cryptographic protocol. A homomorphism between skeletons is an information-preserving map. Much protocol analysis may be regarded as an exploration of the properties of the category of skeletons and homomorphisms. In particular, the strand space authentication tests are special homomorphisms. These ideas su...

We show that a planar graph with girth at least 20t−2 3 has circular chromatic number at most 2+ 1t , improving earlier results. This follows from a general result establishing homomorphisms into special targets for graphs with given girth and given maximum average degree. Other applications concern oriented chromatic number and homomorphisms into mixed graphs with colored edges.

We prove a q-analogue of the Carter–Payne theorem in the case where the differences between the parts of the partitions are sufficiently large. We identify a layer of the Jantzen filtration which contains the image of these Carter–Payne homomorphisms and we show how these homomorphisms compose.

In this paper we establish a dichotomy theorem for the complexity of homomorphisms to fixed locally semicomplete digraphs. It is also shown that the same dichotomy holds for list homomorphisms. The polynomial algorithms follow from a different, shorter proof of a result by Gutjahr, Welzl and Woeginger.