Change search
Refine search result
1 - 18 of 18
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Aas, Erik
    et al.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
    Sjöstrand, Jonas
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
    A product formula for the TASEP on a ring2016In: Random structures & algorithms (Print), ISSN 1042-9832, E-ISSN 1098-2418, Vol. 48, no 2, p. 247-259Article in journal (Refereed)
    Abstract [en]

    For a random permutation sampled from the stationary distributionof the TASEP on a ring, we show that, conditioned on the event that the rstentries are strictly larger than the last entries, the order of the rst entries isindependent of the order of the last entries. The proof uses multi-line queues asdened by Ferrari and Martin, and the theorem has an enumerative combinatorialinterpretation in that setting.As an application we prove a conjecture of Lam and Williams concerningSchubert factors of the stationary probability of certain states.Finally, we present a conjecture for the case where the small and large entriesare not separated.

  • 2. Enquist, Magnus
    et al.
    Strimling, Pontus
    Eriksson, Kimmo
    Laland, Kevin
    Sjöstrand, Jonas
    Mälardalens högskola.
    One cultural parent makes no culture2010In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 79, no 6, p. 1135-1162Article in journal (Refereed)
    Abstract [en]

    The ability to acquire knowledge and skills from others is widespread in animals and is commonly thought to be responsible for the behavioural traditions observed in many species. However, in spite of the extensive literature on theoretical analyses and empirical studies of social learning, little attention has been given to whether individuals acquire knowledge from a single individual or multiple models. Researchers commonly refer to instances of sons learning from fathers, or daughters from mothers, while theoreticians have constructed models of uniparental transmission, with little consideration of whether such restricted modes of transmission are actually feasible. We used mathematical models to demonstrate that the conditions under which learning from a single cultural parent can lead to stable culture are surprisingly restricted (the same reasoning applies to a single social-learning event). Conversely, we demonstrate how learning from more than one cultural parent can establish culture, and find that cultural traits will reach a nonzero equilibrium in the population provided the product of the fidelity of social learning and the number of cultural parents exceeds 1. We discuss the implications of the analysis for interpreting various findings in the animal social-learning literature, as well as the unique features of human culture.

  • 3. Eriksen, Niklas
    et al.
    Sjöstrand, Jonas
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
    Equidistributed Statistics on Matchings and Permutations2014In: The Electronic Journal of Combinatorics, ISSN 1097-1440, E-ISSN 1077-8926, Vol. 21, no 4, article id P4.43Article in journal (Refereed)
    Abstract [en]

    We show that the bistatistic of right nestings and right crossings in matchings without left nestings is equidistributed with the number of occurrences of two certain patterns in permutations, and furthermore that this equidistribution holds when refined to positions of these statistics in matchings and permutations. For this distribution we obtain a non-commutative generating function which specializes to Zagier's generating function for the Fishburn numbers after abelianization. As a special case we obtain proofs of two conjectures of Claesson and Linusson. Finally, we conjecture that our results can be generalized to involving left crossings of matchings too.

  • 4. Eriksson, Kimmo
    et al.
    Jansson, Fredrik
    Sjöstrand, Jonas
    Stockholms universitet.
    Bentley's conjecture on popularity toplist turnover under random copying2010In: The Ramanujan journal, ISSN 1382-4090, E-ISSN 1572-9303, Vol. 23, p. 371-396Article in journal (Refereed)
    Abstract [en]

    Bentley et al studied the turnover rate in popularity toplists in a ’random copying’ model of cultural evolution. Based on simulations of a model with population size N, list length ℓ and invention rate μ, they conjectured a remarkably simple formula for the turnover rate: ℓ√μ. Here we study an overlapping generations version of the random copying model, which can be interpreted as a random walk on the integer partitions of the population size. In this model we show that the conjectured formula, after a slight correction, holds asymptotically.

  • 5.
    Eriksson, Kimmo
    et al.
    Malardalen Univ, Sch Educ Culture & Commun, Box 883, S-72123 Vasteras, Sweden..
    Jonsson, Markus
    Malardalen Univ, Sch Educ Culture & Commun, Box 883, S-72123 Vasteras, Sweden..
    Sjöstrand, Jonas
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Markov Chains on Graded Posets Compatibility of Up-Directed and Down-Directed Transition Probabilities2018In: Order, ISSN 0167-8094, E-ISSN 1572-9273, Vol. 35, no 1, p. 93-109Article in journal (Refereed)
    Abstract [en]

    We consider two types of discrete-time Markov chains where the state space is a graded poset and the transitions are taken along the covering relations in the poset. The first type of Markov chain goes only in one direction, either up or down in the poset (an up chain or down chain). The second type toggles between two adjacent rank levels (an up-and-down chain). We introduce two compatibility concepts between the up-directed transition probabilities (an up rule) and the down-directed (a down rule), and we relate these to compatibility between up-and-down chains. This framework is used to prove a conjecture about a limit shape for a process on Young's lattice. Finally, we settle the questions whether the reverse of an up chain is a down chain for some down rule and whether there exists an up or down chain at all if the rank function is not bounded.

  • 6.
    Eriksson, Kimmo
    et al.
    Mälardalen University, School of Education, Culture and Communication.
    Sjöstrand, Jonas
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Limiting shapes of birth-and-death processes on Young diagrams2012In: Advances in Applied Mathematics, ISSN 0196-8858, E-ISSN 1090-2074, Vol. 48, no 4, p. 575-602Article in journal (Refereed)
    Abstract [en]

    We consider a family of birth processes and birth-and-death processes on Young diagrams of integer partitions of n. This family incorporates three famous models from very different fields: Rost's totally asymmetric particle model (in discrete time), Simon's urban growth model, and Moran's infinite alleles model. We study stationary distributions and limit shapes as n tends to infinity, and present a number of results and conjectures.

  • 7. Eriksson, Kimmo
    et al.
    Sjöstrand, Jonas
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
    On two theorems of Quinzii and rent controlled housing allocation in Sweden2007In: International Journal of Game Theory, ISSN 0020-7276, E-ISSN 1432-1270, Vol. 3, no 9, p. 515-526Article in journal (Refereed)
    Abstract [en]

    The Swedish rent control system creates a white market for swapping rental contracts and a black market for selling rental contracts. Empirical data suggests that in this black-and-white market some people act according to utility functions that are both discontinuous and locally decreasing in money. We discuss Quinzii's theorem for the nonemptiness of the core of generalized house-swapping games, and show how it can be extended to cover the Swedish game. In a second part, we show how this theorem of Quinzii and her second theorem on nonemptiness of the core in two-sided models are both special cases of a more general theorem.

  • 8. Eriksson, Kimmo
    et al.
    Sjöstrand, Jonas
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Strimling, Pontus
    Asymmetric equilibria in dynamic two-sided matching markets with independent preferences2008In: International Journal of Game Theory, ISSN 0020-7276, E-ISSN 1432-1270, Vol. 36, no 3-4, p. 421-440Article in journal (Refereed)
    Abstract [en]

    A fundamental fact in two-sided matching is that if a market allows several stable outcomes, then one is optimal for all men in the sense that no man would prefer another stable outcome. We study a related phenomenon of asymmetric equilibria in a dynamic market where agents enter and search for a mate for at most n rounds before exiting again. Assuming independent preferences, we find that this game has multiple equilibria, some of which are highly asymmetric between sexes. We also investigate how the set of equilibria depends on a sex difference in the outside option of not being mated at all.

  • 9.
    Eriksson, Kimmo
    et al.
    Malardalen Univ, Dept Math & Phys.
    Sjöstrand, Jonas
    Malardalen Univ, Dept Math & Phys.
    Strimling, Pontus
    Malardalen Univ, Dept Math & Phys.
    Optimal expected rank in a two-sided secretary problem2007In: Operations Research, ISSN 0030-364X, E-ISSN 1526-5463, Vol. 55, no 5, p. 921-931Article in journal (Refereed)
    Abstract [en]

    In a two-sided version of the famous secretary problem, employers search for a secretary at the same time as secretaries search for an employer. Nobody accepts being put on hold, and nobody is willing to take part in more than N interviews. Preferences are independent, and agents seek to optimize the expected rank of the partner they obtain among the N potential partners. We find that in any subgame perfect equilibrium, the expected rank grows as the square root of N (whereas it tends to a constant in the original secretary problem). We also compute how much agents can gain by cooperation.

  • 10. Eriksson, Kirnmo
    et al.
    Sjöstrand, Jonas
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Strimling, Pontus
    Three-dimensional stable matching with cyclic preferences2006In: Mathematical Social Sciences, ISSN 0165-4896, E-ISSN 1879-3118, Vol. 52, no 1, p. 77-87Article in journal (Refereed)
    Abstract [en]

    We consider stable three-dimensional matchings of three genders (3GSM). Alkan [Alkan, A., 1988. Nonexistence of stable threesome matchings. Mathematical Social Sciences 16, 207-209] showed that not all instances of 3GSM allow stable matchings. Boros et al. [Boros, E., Gurvich, V, Jaslar, S., Krasner, D., 2004. Stable matchings in three-sided systems with cyclic preferences. Discrete Mathematics 286, 1-10] showed that if preferences are cyclic, and the number of agents is limited to three of each gender, then a stable matching always exists. Here we extend this result to four agents of each gender. We also show that a number of well-known sufficient conditions for stability do not apply to cyclic 3GSM. Based on computer search, we formulate a conjecture on stability of "strongest link" 3GSM, which would imply stability of cyclic 3GSM.

  • 11.
    Sjöstrand, Jonas
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Bruhat intervals as rooks on skew Ferrers boards2007In: Journal of combinatorial theory. Series A (Print), ISSN 0097-3165, E-ISSN 1096-0899, Vol. 114, no 7, p. 1182-1198Article in journal (Refereed)
    Abstract [en]

    We characterise the permutations pi such that the elements in the closed lower Bruhat interval [id, pi] of the symmetric group correspond to non-taking rook configurations on a skew Ferrers board. It turns out that these are exactly the permutations pi such that [id, pi] corresponds to a flag manifold defined by inclusions, studied by Gasharov and Reiner.Our characterisation connect, the Poincare polynomials (rank-generating function) of Bruhat intervals with q-rook polynomials, and we are able to compute the Poincare polynomial of some particularly interesting intervals in the finite Weyl groups An and B, The expressions involve q-Stirling numbers of the second kind, and for the group A, putting q = 1 yields the poly-Bernoulli numbers defined by Kaneko.

  • 12.
    Sjöstrand, Jonas
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Cylindrical lattice walks and the Loehr-Warrington 10(n) conjecture2007In: European journal of combinatorics (Print), ISSN 0195-6698, E-ISSN 1095-9971, Vol. 28, no 3, p. 774-780Article in journal (Refereed)
    Abstract [en]

    There are 10(n) zero-sum words of length 5n in the alphabet {+3, -2} such that no zero-sum consecutive subword that starts with +3 may be followed immediately by -2.

    We give a simple bijective proof of the conjecture in its original and more general setting. To do this we reformulate the problem in terms of cylindrical lattice walks.

  • 13.
    Sjöstrand, Jonas
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Enumerative combinatorics related to partition shapes2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis deals with enumerative combinatorics applied to three different objects related to partition shapes, namely tableaux, restricted words, and Bruhat intervals. The main scientific contributions are the following.

    Paper I: Let the sign of a standard Young tableau be the sign of the permutation you get by reading it row by row from left to right, like a book. A conjecture by Richard Stanley says that the sum of the signs of all SYTs with n squares is 2^[n/2]. We prove a generalisation of this conjecture using the Robinson-Schensted correspondence and a new concept called chess tableaux. The proof is built on a remarkably simple relation between the sign of a permutation pi and the signs of its RS-corresponding tableaux P and Q, namely sgn(pi) = (−1)^v sgn(P)sgn(Q), where v is the number of disjoint vertical dominoes that fit in the partition shape of P and Q. The sign-imbalance of a partition shape is defined as the sum of the signs of all standard Young tableaux of that shape. As a further application of the sign-transferring formula above, we also prove a sharpening of another conjecture by Stanley concerning weighted sums of squares of sign-imbalances.

    Paper II: We generalise some of the results in paper I to skew tableaux. More precisely, we examine how the sign property is transferred by the skew Robinson-Schensted correspondence invented by Sagan and Stanley. The result is a surprisingly simple generalisation of the ordinary non-skew formula above. As an application, we find vanishing weighted sums of squares of sign-imbalances, thereby generalising a variant of Stanley’s second conjecture.

    Paper III: The following special case of a conjecture by Loehr and Warrington was proved by Ekhad, Vatter, and Zeilberger: There are 10^n zero-sum words of length 5n in the alphabet {+3,−2} such that no consecutive subword begins with +3, ends with −2, and sums to −2. We give a simple bijective proof of the conjecture in its original and more general setting where 3 and 2 are replaced by any relatively prime positive integers a and b, 10^n is replaced by ((a+b) choose a)^n, and 5n is replaced by (a+b)n. To do this we reformulate the problem in terms of cylindrical lattice walks which can be interpreted as the south-east border of certain partition shapes.

    Paper IV: We characterise the permutations pi such that the elements in the closed lower Bruhat interval [id,pi] of the symmetric group correspond to non-capturing rook configurations on a skew Ferrers board. These intervals turn out to be exactly those whose flag manifolds are defined by inclusions, as defined by Gasharov and Reiner. The characterisation connects Poincaré polynomials (rank-generating functions) of Bruhat intervals with q-rook polynomials, and we are able to compute the Poincaré polynomial of some particularly interesting intervals in the finite Weyl groups A_n and B_n. The expressions involve q-Stirling numbers of the second kind, and for the group A_n putting q = 1 yields the poly-Bernoulli numbers defined by Kaneko.

  • 14.
    Sjöstrand, Jonas
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematics (Div.).
    Expected length of a product of random reflections2012In: Proceedings of the American Mathematical Society, ISSN 0002-9939, E-ISSN 1088-6826, Vol. 140, no 12, p. 4369-4380Article in journal (Refereed)
    Abstract [en]

    We present a simple formula for the expected number of inversions in a permutation of size n obtained by applying t random (not necessarily adjacent) transpositions to the identity permutation. More generally, for any finite irreducible Coxeter group belonging to one of the infinite families (type A, B, D, and I), an exact expression is obtained for the expected length of a product of t random reflections.

  • 15.
    Sjöstrand, Jonas
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    On the sign-imbalance of partition shapes2005In: Journal of combinatorial theory. Series A (Print), ISSN 0097-3165, E-ISSN 1096-0899, Vol. 111, no 2, p. 190-203Article in journal (Refereed)
    Abstract [en]

    Let the sign of a standard Young tableau be the sign of the permutation you get by reading it row by row from left to right, like a book. A conjecture by Richard Stanley says that the sum of the signs of all SYTs with n squares is 2([n/2]). We present a stronger theorem with a purely combinatorial proof using the Robinson-Schensted correspondence and a new concept called chess tableaux. We also prove a sharpening of another conjecture by Stanley concerning weighted sums of squares of sign-imbalances. The proof is built on a remarkably simple relation between the sign of a permutation and the signs of its RS-corresponding tableaux.

  • 16.
    Sjöstrand, Jonas
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    On the sign-imbalance of skew partition shapes2007In: European journal of combinatorics (Print), ISSN 0195-6698, E-ISSN 1095-9971, Vol. 28, no 6, p. 1582-1594Article in journal (Refereed)
    Abstract [en]

    Let the sign of a skew standard Young tableau be the sign of the permutation you get by reading it row by row from left to right, like a book. We examine how the sign property is transferred by the skew Robinson-Schensted correspondence invented by Sagan and Stanley. The result is a remarkably simple generalization of the ordinary non-skew formula.The sum of the signs of all standard tableaux on a given skew shape is the sign-imbalance of that shape. We generalize previous results on the sign-imbalance of ordinary partition shapes to skew ones.

  • 17.
    Sjöstrand, Jonas
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    The cover pebbling theorem2005In: The Electronic Journal of Combinatorics, ISSN 1097-1440, E-ISSN 1077-8926, Vol. 12, no 1, p. N22-Article in journal (Refereed)
    Abstract [en]

    For any configuration of pebbles on the nodes of a graph, a pebbling move replaces two pebbles on one node by one pebble on an adjacent node. A cover pebbling is a move sequence ending with no empty nodes. The number of pebbles needed for a cover pebbling starting with all pebbles on one node is trivial to compute and it was conjectured that the maximum of these simple cover pebbling numbers is indeed the general cover pebbling number of the graph. That is, for any configuration of this size, there exists a cover pebbling. In this note, we prove a generalization of the conjecture. All previously published results about cover pebbling numbers for special graphs (trees, hypercubes et cetera) are direct consequences of this theorem. We also prove that the cover pebbling number of a product of two graphs equals the product of the cover pebbling numbers of the graphs.

  • 18. Strimling, Pontus
    et al.
    Sjöstrand, Jonas
    Centre for the Study of Cultural Evolution, Stockholm University.
    Accumulation of independent cultural traits2009In: Theoretical Population Biology, ISSN 0040-5809, E-ISSN 1096-0325, Vol. 76, no 2, p. 77-83Article in journal (Refereed)
    Abstract [en]

    In a species capable of (imperfect) social learning, how much culture can a population of a given size carry? And what is the relationship between the individual and the population? In the first study of these novel questions, here we develop a mathematical model of the accumulation of independent cultural traits in a finite population with overlapping generations.

1 - 18 of 18
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf