TY  - JOUR
A1  - Dimitrova, Ilinka
A1  - Koppitz, Jörg
T1  - On the semigroup of all partial fence-preserving injections on a finite set
JF  - Journal of Algebra and Its Applications
N2  - For n∈N , let Xn={a1,a2,…,an} be an n-element set and let F=(Xn;<f) be a fence, also called a zigzag poset. As usual, we denote by In the symmetric inverse semigroup on Xn. We say that a transformation α∈In is fence-preserving if x<fy implies that xα<fyα, for all x,y in the domain of α. In this paper, we study the semigroup PFIn of all partial fence-preserving injections of Xn and its subsemigroup IFn={α∈PFIn:α−1∈PFIn}. Clearly, IFn is an inverse semigroup and contains all regular elements of PFIn. We characterize the Green’s relations for the semigroup IFn. Further, we prove that the semigroup IFn is generated by its elements with rank ≥n−2. Moreover, for n∈2N, we find the least generating set and calculate the rank of IFn.
KW  - Finite transformation semigroup
KW  - fence-preserving transformations
KW  - inverse semigroup
KW  - Green´s Relations
KW  - generators
KW  - rank
Y1  - 2017
U6  - https://doi.org/10.1142/S0219498817502231
SN  - 0219-4988
SN  - 1793-6829
VL  - 16
IS  - 12
PB  - World Scientific
CY  - Singapore
ER  - 
TY  - JOUR
A1  - Dimitrova, Ilinka
A1  - Koppitz, Jörg
T1  - On some anti-inverse transformation semigroups
N2  - A semigroup S is called anti-inverse if for all a E S there is a b is an element of S such that aba = b and bab = a. Each anti-inverse semigroup is regular. In the present paper, we study anti-inverse subsemigroups within the semigroup T-n of all transformations on an n-element set (1 <= n is an element of N). In particular, we characterize all anti-inverse semigroups within the J-classes of T-n and illustrate our result by four examples.
Y1  - 2010
UR  - http://www.proceedings.bas.bg/
SN  - 1310-1331
ER  - 
TY  - JOUR
A1  - Dimitrova, Ilinka
A1  - Koppitz, Jörg
T1  - On the monoid of all partial order-preserving extensive transformations
JF  - Communications in algebra
N2  - A partial transformation alpha on an n-element chain X-n is called order-preserving if x <= y implies x alpha <= y alpha for all x, y in the domain of alpha and it is called extensive if x <= x alpha for all x in the domain of alpha. The set of all partial order-preserving extensive transformations on X-n forms a semiband POEn. We determine the maximal subsemigroups as well as the maximal subsemibands of POEn.
KW  - Extensive transformation
KW  - Maximal subsemibands
KW  - Maximal subsemigroups
KW  - Rank
KW  - Transformation semigroup
Y1  - 2012
U6  - https://doi.org/10.1080/00927872.2011.557813
SN  - 0092-7872
VL  - 40
IS  - 5
SP  - 1821
EP  - 1826
PB  - Taylor & Francis Group
CY  - Philadelphia
ER  - 
TY  - JOUR
A1  - Dimitrova, Ilinka
A1  - Koppitz, Jörg
T1  - On the maximal regular subsemigroups of ideals of order-preserving or order-reversing transformations
JF  - Semigroup forum
N2  - We characterize the maximal regular subsemigroups of the ideals of the semigroup of all order-preserving transformations as well as of the semigroup of all order-preserving or order-reversing transformations on a finite ordered set.
KW  - Transformation semigroups
KW  - Regular semigroups
KW  - Order-preserving transformations
KW  - Order-reversing transformations
KW  - Maximal subsemigroups
Y1  - 2011
U6  - https://doi.org/10.1007/s00233-010-9272-8
SN  - 0037-1912
VL  - 82
IS  - 1
SP  - 172
EP  - 180
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Dimitrova, Ilinka
A1  - Koppitz, Jörg
T1  - On relative ranks of the semigroup of orientation-preserving transformations on infinite chain with restricted range
JF  - Communications in algebra
N2  - Let X be an infinite linearly ordered set and let Y be a nonempty subset of X. We calculate the relative rank of the semigroup OP(X,Y) of all orientation-preserving transformations on X with restricted range Y modulo the semigroup O(X,Y) of all order-preserving transformations on X with restricted range Y. For Y = X, we characterize the relative generating sets of minimal size.
KW  - Order-preserving transformations
KW  - orientation-preserving
KW  - transformations
KW  - relative rank
KW  - restricted range
KW  - transformation
KW  - semigroups on infinite chain
Y1  - 2022
U6  - https://doi.org/10.1080/00927872.2021.2000998
SN  - 0092-7872
SN  - 1532-4125
VL  - 50
IS  - 5
SP  - 2157
EP  - 2168
PB  - Taylor & Francis Group
CY  - Philadelphia
ER  - 
TY  - JOUR
A1  - Dimitrova, Ilinka
A1  - Koppitz, Jörg
T1  - On relative ranks of the semigroup of orientation-preserving transformations on infinite chains
JF  - Asian-European journal of mathematics
N2  - In this paper, we determine the relative rank of the semigroup OP(X) of all orientation-preserving transformations on infinite chains modulo the semigroup O(X) of all order-preserving transformations.
KW  - Transformation semigroups on infinite chains
KW  - order-preserving
KW  - transformations
KW  - orientation-preserving transformations
KW  - relative rank
Y1  - 2020
U6  - https://doi.org/10.1142/S1793557121501461
SN  - 1793-5571
SN  - 1793-7183
VL  - 14
IS  - 08
PB  - World Scientific
CY  - Singapore
ER  - 
TY  - JOUR
A1  - Dimitrova, Ilinka
A1  - Fernandes, Vitor H.
A1  - Koppitz, Jörg
T1  - A note on generators of the endomorphism semigroup of an infinite countable chain
JF  - Journal of Algebra and its Applications
N2  - In this note, we consider the semigroup O(X) of all order endomorphisms of an infinite chain X and the subset J of O(X) of all transformations alpha such that vertical bar Im(alpha)vertical bar = vertical bar X vertical bar. For an infinite countable chain X, we give a necessary and sufficient condition on X for O(X) = < J > to hold. We also present a sufficient condition on X for O(X) = < J > to hold, for an arbitrary infinite chain X.
KW  - Infinite chain
KW  - endomorphism semigroup
KW  - generators
KW  - relative rank
Y1  - 2016
U6  - https://doi.org/10.1142/S0219498817500311
SN  - 0219-4988
SN  - 1793-6829
VL  - 16
IS  - 2
PB  - World Scientific
CY  - Singapore
ER  - 
TY  - JOUR
A1  - Dimitrova, Ilinka
A1  - Fernandes, Vitor H.
A1  - Koppitz, Jörg
T1  - The maximal subsemigroups of semigroups of transformations preserving or reversing the orientation on a finite chain
JF  - Publicationes mathematicae
N2  - The study of the semigroups OPn, of all orientation-preserving transformations on an n-element chain, and ORn, of all orientation-preserving or orientation-reversing transformations on an n-element chain, has began in [17] and [5]. In order to bring more insight into the subsemigroup structure of OPn and ORn, we characterize their maximal subsemigroups.
KW  - finite transformation semigroup
KW  - orientation-preserving and orientation-reversing transformations
KW  - maximal subsemigroups
Y1  - 2012
U6  - https://doi.org/10.5486/PMD.2012.4897
SN  - 0033-3883
VL  - 81
IS  - 1-2
SP  - 11
EP  - 29
PB  - Institutum Mathematicum Universitatis Debreceniensis, Debreceni Tudományegyetem Matematikai Intézete
CY  - Debrecen
ER  - 
TY  - THES
A1  - Dimitrova, Ilinka
T1  - Greenïs equivalences on some classes of transformation semigroups
Y1  - 2006
CY  - Potsdam
ER  -