Search results for "If and only if"
showing 10 items of 36 documents
A note on endomorphisms of hypercentral groups
2002
Abstract Let H be a subnormal subgroup of a hypercentral group G. We prove that endomorphisms of G are uniquely determined by their restrictions to H if and only if Hom(G/HG,G)=0, and draw some consequences from this fact.
Trade Associations: Why Not Cartels?
2021
First published: 30 September 2020 The relevance of special interests lobbying in modern democracies can hardly be questioned. But if large trade associations can overcome the free riding problem and form effective lobbies, why do they not also threaten market competition by forming equally effective cartels? We argue that the key to understanding the difference lies in supply elasticity. The group discipline which works in the case of lobbying can be effective in sustaining a cartel only if increasing output is sufficiently costly ‐ otherwise the incentive to deviate is too great. The theory helps organizing a number of stylized facts within a common framework. This article has been accept…
Distributed consensus protocols for coordinating buyers
2003
In this paper, we introduce a distributed consensus protocol for coordinating orders of a network of buyers also called agents/decision makers. Each buyer chooses a different threshold strategy, defining its intention to place an order only if at least other l buyers will do the same. We prove that consensus is reached asymptotically globally and coordination is the same that if the decision making process would be centralized, namely, any decision maker (DM) has access to the thresholds of all other DMs and chooses to order or not. The proposed distributed protocol has the advantage that buyers do not have to communicate their threshold strategy in advance, and consensus is reached without…
A characterization of the n-ary many-sorted closure operators and a many-sorted Tarski irredundant basis theorem
2018
A theorem of single-sorted algebra states that, for a closure space (A, J ) and a natural number n, the closure operator J on the set A is n-ary if and only if there exists a single-sorted signature Σ and a Σ-algebra A such that every operation of A is of an arity ≤ n and J = SgA, where SgA is the subalgebra generating operator on A determined by A. On the other hand, a theorem of Tarski asserts that if J is an n-ary closure operator on a set A with n ≥ 2, then, for every i, j ∈ IrB(A, J ), where IrB(A, J ) is the set of all natural numbers which have the property of being the cardinality of an irredundant basis (≡ minimal generating set) of A with respect to J , if i < j and {i + 1, . . . …
Popularity of patterns over $d$-equivalence classes of words and permutations
2020
Abstract Two same length words are d-equivalent if they have same descent set and same underlying alphabet. In particular, two same length permutations are d-equivalent if they have same descent set. The popularity of a pattern in a set of words is the overall number of copies of the pattern within the words of the set. We show the far-from-trivial fact that two patterns are d-equivalent if and only if they are equipopular over any d-equivalence class, and this equipopularity does not follow obviously from a trivial equidistribution.
Innovative Changes for Reaching Sustainability in Universities
2013
Abstract This paper presents an original approach to the changes required for the transformation of universities in sustainable universities. The focus is on the innovative approach of all activities and relationships of the university: teaching, scientific research and other services offered by the university, the relations of the university with the communities where it operates, inter-university relations, relations with business environment, etc. Based on the experience and information gathered by the authors in the strategic project “Improving University Management”, it is proposed a better, more efficient and more effective way of using the resources of universities, thus sharing the …
HETEROGENEITY IN RISK PREFERENCES LEADS TO STOCHASTIC VOLATILITY
2018
This paper studies the price processes of a claim on terminal endowment and of a claim on firm book value when the underlying variables follow a bivariate geometric Brownian motion. If the state-price process is multiplicatively separable into time and endowment functions, our main result shows that firm (endowment) price volatility is stochastic (state-dependent) if, and only if, the endowment function is not a power function. In a pure exchange economy populated by two agents with constant relative risk aversion (CRRA) preferences we confirm the separability, and we show furthermore that firm (endowment) price volatility is stochastic (state-dependent) if, and only if, both agents are he…
Minimal Forbidden Factors of Circular Words
2017
Minimal forbidden factors are a useful tool for investigating properties of words and languages. Two factorial languages are distinct if and only if they have different (antifactorial) sets of minimal forbidden factors. There exist algorithms for computing the minimal forbidden factors of a word, as well as of a regular factorial language. Conversely, Crochemore et al.ÃÂ [IPL, 1998] gave an algorithm that, given the trie recognizing a finite antifactorial language M, computes a DFA of the language having M as set of minimal forbidden factors. In the same paper, they showed that the obtained DFA is minimal if the input trie recognizes the minimal forbidden factors of a single word. We gener…
Verb inflection in Ancient Greek and Sanskrit and auxiliation patterns in French and Italian. Forms, functions, system
2009
This paper deals with the complex interaction between form and function in the verb morphosyntax of four Indo-European languages (French, Italian, Ancient Greek and Sanskrit). Beyond the difference in form, auxiliation patterns in French and Italian, and verb inflections in Ancient Greek and Sanskrit correlate, thanks to the agreement for number and person, to the expression of the relationship with the Subject. The different auxiliation patterns (sum and habeo) and the different inflections (middle and active) correlate to different properties of the Subject. In particular, these forms depend on the syntactic opposition between middle and non-middle. The ways of this dependency are regulat…
MLU and IPSyn measuring absolute complexity
2009
This article compares the results of Mean Length of Utterance (MLU) and Index of Productive Syntax (IPSyn) with the structural complexity of spontaneous utterances produced by 30-month-old Finnish children in a semi-structured playing situation. The comparison was carried out in order to determine the aspects of structural complexity which can be detected with MLU and IPSyn. This research adopts the frameworks of absolute complexity together with a multidimensional view of utterance structure and, furthermore, applies it through Utterance Analysis (UA). The results of the comparison between the metrics and changes in structural complexity discovered by UA reveal that MLU and IPSyn do functi…