Articles de revista
http://hdl.handle.net/2117/184705
2024-03-28T09:51:19Z
2024-03-28T09:51:19Z
Extremal Sidon sets are Fourier uniform, with applications to partition regularity
Ortega Sánchez Colomer, Miquel
Prendiville, Sean
http://hdl.handle.net/2117/402436
2024-02-26T00:25:43Z
2024-02-21T12:27:39Z
Extremal Sidon sets are Fourier uniform, with applications to partition regularity
Ortega Sánchez Colomer, Miquel; Prendiville, Sean
Generalising results of Erdos-Freud and Lindström, we prove that the largest Sidon subset of a bounded interval of integers is equidistributed in Bohr neighbourhoods. We establish this by showing that extremal Sidon sets are Fourier-pseudorandom, in that they have no large non-trivial Fourier coefficients. As a further application we deduce that, for any partition regular equation in five or more variables, every finite colouring of an extremal Sidon set has a monochromatic solution.
2024-02-21T12:27:39Z
Ortega Sánchez Colomer, Miquel
Prendiville, Sean
Generalising results of Erdos-Freud and Lindström, we prove that the largest Sidon subset of a bounded interval of integers is equidistributed in Bohr neighbourhoods. We establish this by showing that extremal Sidon sets are Fourier-pseudorandom, in that they have no large non-trivial Fourier coefficients. As a further application we deduce that, for any partition regular equation in five or more variables, every finite colouring of an extremal Sidon set has a monochromatic solution.
Some characterizations of resolute majority rules
Freixas Bosch, Josep
Samaniego Vidal, Daniel
http://hdl.handle.net/2117/396926
2023-11-26T21:37:15Z
2023-11-22T19:19:12Z
Some characterizations of resolute majority rules
Freixas Bosch, Josep; Samaniego Vidal, Daniel
In this paper we consider decision functions in which voters have three options and one of them is abstention or indifference and the output is a binary decision between two alternatives so that a tie is not possible. These resolute decision functions appear frequently in grading, in some sport competitions, in voting situations in which the status quo is put to the vote, etc. It is a more restricted case of the voting context considered in the seminal article by Kenneth May on decision functions, published in Econometrica in 1952, because the output set does not admit a tie. Among these resolute decision functions we focus on the study of majority functions, in which the number of favorable votes to an alternative must be strictly greater than the number of votes against it. This work provides an axiomatic characterization for the set of majority functions and for the relative majority function with status quo bias. Both characterizations are based on weaker versions of neutrality. Other complementary characterizations are also provided.
The version of record of this article, first published in Annals of Operations Research, is available online at Publisher’s website: http://dx.doi.org/10.1007/s10479-023-05621-x
2023-11-22T19:19:12Z
Freixas Bosch, Josep
Samaniego Vidal, Daniel
In this paper we consider decision functions in which voters have three options and one of them is abstention or indifference and the output is a binary decision between two alternatives so that a tie is not possible. These resolute decision functions appear frequently in grading, in some sport competitions, in voting situations in which the status quo is put to the vote, etc. It is a more restricted case of the voting context considered in the seminal article by Kenneth May on decision functions, published in Econometrica in 1952, because the output set does not admit a tie. Among these resolute decision functions we focus on the study of majority functions, in which the number of favorable votes to an alternative must be strictly greater than the number of votes against it. This work provides an axiomatic characterization for the set of majority functions and for the relative majority function with status quo bias. Both characterizations are based on weaker versions of neutrality. Other complementary characterizations are also provided.
Cospectral mates for generalized Johnson and Grassmann graphs
Abiad Monge, Aida
D'haeseleer, Jozefien
Haemers, Willem H.
Simoens, Robin Nicolas
http://hdl.handle.net/2117/396615
2023-11-26T01:49:53Z
2023-11-17T11:54:06Z
Cospectral mates for generalized Johnson and Grassmann graphs
Abiad Monge, Aida; D'haeseleer, Jozefien; Haemers, Willem H.; Simoens, Robin Nicolas
We provide three infinite families of graphs in the Johnson and Grassmann schemes that are not uniquely determined by their spectrum. We do so by constructing graphs that are cospectral but non-isomorphic to these graphs.
2023-11-17T11:54:06Z
Abiad Monge, Aida
D'haeseleer, Jozefien
Haemers, Willem H.
Simoens, Robin Nicolas
We provide three infinite families of graphs in the Johnson and Grassmann schemes that are not uniquely determined by their spectrum. We do so by constructing graphs that are cospectral but non-isomorphic to these graphs.
Particle realization of Bondi-Metzner-Sachs symmetry in 2 + 1 space-time
Batlle Arnau, Carles
Campello Román, Víctor Manuel
Gomis Torné, Joaquin
http://hdl.handle.net/2117/396178
2023-11-13T09:27:18Z
2023-11-09T12:04:32Z
Particle realization of Bondi-Metzner-Sachs symmetry in 2 + 1 space-time
Batlle Arnau, Carles; Campello Román, Víctor Manuel; Gomis Torné, Joaquin
We construct a Lorentz invariant massive particle model in (2+1) space-time with an enlarged set of symmetries which includes Bondi-Metzner-Sachs (BMS) translations (supertranslations), using the non-linear realization framework. The Hamiltonian formalism for the resulting Lagrangian is constructed, and the infinite phase-space constraints and the set of gauge transformations are analysed. We also compute the massless limit of the theory in phase-space. After eliminating the gauge degrees of freedom, the physical reduced space is left only with the degrees of freedom of a standard Poincaré particle but with a residual set of symmetries that we prove to be BMS. A similar result for the massless limit, including in this case superrotations, is pointed out.
2023-11-09T12:04:32Z
Batlle Arnau, Carles
Campello Román, Víctor Manuel
Gomis Torné, Joaquin
We construct a Lorentz invariant massive particle model in (2+1) space-time with an enlarged set of symmetries which includes Bondi-Metzner-Sachs (BMS) translations (supertranslations), using the non-linear realization framework. The Hamiltonian formalism for the resulting Lagrangian is constructed, and the infinite phase-space constraints and the set of gauge transformations are analysed. We also compute the massless limit of the theory in phase-space. After eliminating the gauge degrees of freedom, the physical reduced space is left only with the degrees of freedom of a standard Poincaré particle but with a residual set of symmetries that we prove to be BMS. A similar result for the massless limit, including in this case superrotations, is pointed out.
A mechanical G2 checkpoint controls epithelial cell division through E-cadherin-mediated regulation of Wee1-Cdk1
Donker, Lisa
Houtekamer, Ronja
Vliem, Marjolein
Sipieter, François
Canever, Helena
Gómez González, Manuel
Bosch Padrós, Miquel
Pannekoek, Willem Jan
Trepat Guixer, Xavier
Borghi, Nicolas
Gloerich, Martijn
http://hdl.handle.net/2117/395901
2023-11-13T09:28:32Z
2023-11-07T10:00:40Z
A mechanical G2 checkpoint controls epithelial cell division through E-cadherin-mediated regulation of Wee1-Cdk1
Donker, Lisa; Houtekamer, Ronja; Vliem, Marjolein; Sipieter, François; Canever, Helena; Gómez González, Manuel; Bosch Padrós, Miquel; Pannekoek, Willem Jan; Trepat Guixer, Xavier; Borghi, Nicolas; Gloerich, Martijn
Epithelial cell divisions are coordinated with cell loss to preserve epithelial integrity. However, how epithelia adapt their rate of cell division to changes in cell number, for instance during homeostatic turnover or wounding, is not well understood. Here, we show that epithelial cells sense local cell density through mechanosensitive E-cadherin adhesions to control G2/M cell-cycle progression. As local cell density increases, tensile forces on E-cadherin adhesions are reduced, which prompts the accumulation of the G2 checkpoint kinase Wee1 and downstream inhibitory phosphorylation of Cdk1. Consequently, dense epithelia contain a pool of cells that are temporarily halted in G2 phase. These cells are readily triggered to divide following epithelial wounding due to the consequent increase in intercellular forces and resulting degradation of Wee1. Our data collectively show that epithelial cell division is controlled by a mechanical G2 checkpoint, which is regulated by cell-density-dependent intercellular forces sensed and transduced by E-cadherin adhesions.
© 2022 The Author(s)
2023-11-07T10:00:40Z
Donker, Lisa
Houtekamer, Ronja
Vliem, Marjolein
Sipieter, François
Canever, Helena
Gómez González, Manuel
Bosch Padrós, Miquel
Pannekoek, Willem Jan
Trepat Guixer, Xavier
Borghi, Nicolas
Gloerich, Martijn
Epithelial cell divisions are coordinated with cell loss to preserve epithelial integrity. However, how epithelia adapt their rate of cell division to changes in cell number, for instance during homeostatic turnover or wounding, is not well understood. Here, we show that epithelial cells sense local cell density through mechanosensitive E-cadherin adhesions to control G2/M cell-cycle progression. As local cell density increases, tensile forces on E-cadherin adhesions are reduced, which prompts the accumulation of the G2 checkpoint kinase Wee1 and downstream inhibitory phosphorylation of Cdk1. Consequently, dense epithelia contain a pool of cells that are temporarily halted in G2 phase. These cells are readily triggered to divide following epithelial wounding due to the consequent increase in intercellular forces and resulting degradation of Wee1. Our data collectively show that epithelial cell division is controlled by a mechanical G2 checkpoint, which is regulated by cell-density-dependent intercellular forces sensed and transduced by E-cadherin adhesions.
Random walks associated with symmetric M-matrices
Carmona Mejías, Ángeles
Encinas Bachiller, Andrés Marcos
Jiménez Jiménez, María José
Martin Llopis, Álvar
http://hdl.handle.net/2117/395569
2023-11-02T08:00:23Z
2023-11-02T07:52:41Z
Random walks associated with symmetric M-matrices
Carmona Mejías, Ángeles; Encinas Bachiller, Andrés Marcos; Jiménez Jiménez, María José; Martin Llopis, Álvar
In this paper we generalize the transition probability matrix for a random walk on a finite network by defining the transition probabilities througha symmetric M-matrix. Usually, the walker jumps from a vertex to a neighboraccording to the probabilities given by the adjacency matrix. Moreover, we can find in the literature the relation between random walks and the normalized laplacian or the combinatorial laplacian that are singular and symmetric M-matrices. Our model takes into consideration not only the probability of transitioning given by the adjacency matrix but also some added probability that depends on a node property. This also includes the probability of remaining in each node, when the M-matrix is not singular. The nodes importance is taking into account by considering the lower eigenvalue and its associated eigenfunction for the given M-matrix. We give expressions for the mean first passage time and Kemeny’s constant for such a random walks in terms of 1-inverses of the considered Mmatrix.
2023-11-02T07:52:41Z
Carmona Mejías, Ángeles
Encinas Bachiller, Andrés Marcos
Jiménez Jiménez, María José
Martin Llopis, Álvar
In this paper we generalize the transition probability matrix for a random walk on a finite network by defining the transition probabilities througha symmetric M-matrix. Usually, the walker jumps from a vertex to a neighboraccording to the probabilities given by the adjacency matrix. Moreover, we can find in the literature the relation between random walks and the normalized laplacian or the combinatorial laplacian that are singular and symmetric M-matrices. Our model takes into consideration not only the probability of transitioning given by the adjacency matrix but also some added probability that depends on a node property. This also includes the probability of remaining in each node, when the M-matrix is not singular. The nodes importance is taking into account by considering the lower eigenvalue and its associated eigenfunction for the given M-matrix. We give expressions for the mean first passage time and Kemeny’s constant for such a random walks in terms of 1-inverses of the considered Mmatrix.
Multisymplectic formalism for cubic horndeski theories
Doniz Hernández, Mauricio
Gaset Rifà, Jordi
http://hdl.handle.net/2117/393895
2023-10-08T11:56:32Z
2023-09-22T08:23:34Z
Multisymplectic formalism for cubic horndeski theories
Doniz Hernández, Mauricio; Gaset Rifà, Jordi
We present the covariant multisymplectic formalism for the so-called cubic Horndeski theories and discuss the geometrical and physical interpretation of the constraints that arise in the uni¿ed Lagrangian-Hamiltonian approach. We analyse in more detail the covariant Hamiltonian formalism of these theories and we show that there are particular conditions that must be satis¿ed for the Poincar´e-Cartan form of the Lagrangian to project onto J1p. From this result, we study when a formulation using only multimomenta is possible. We further discuss the implications of the general case, in which the projection onto J1p conditions are not met.
2023-09-22T08:23:34Z
Doniz Hernández, Mauricio
Gaset Rifà, Jordi
We present the covariant multisymplectic formalism for the so-called cubic Horndeski theories and discuss the geometrical and physical interpretation of the constraints that arise in the uni¿ed Lagrangian-Hamiltonian approach. We analyse in more detail the covariant Hamiltonian formalism of these theories and we show that there are particular conditions that must be satis¿ed for the Poincar´e-Cartan form of the Lagrangian to project onto J1p. From this result, we study when a formulation using only multimomenta is possible. We further discuss the implications of the general case, in which the projection onto J1p conditions are not met.
Single and two-cells shape analysis from energy functionals for three-dimensional vertex models
Khan, Ahmad Kamal
Muñoz Castro, Guillem
Muñoz Romero, José
http://hdl.handle.net/2117/393555
2023-09-17T22:43:03Z
2023-09-15T11:45:19Z
Single and two-cells shape analysis from energy functionals for three-dimensional vertex models
Khan, Ahmad Kamal; Muñoz Castro, Guillem; Muñoz Romero, José
Vertex models have been extensively used for simulating the evolution ofmulticellular systems, and have given rise to important global properties con-cerning their macroscopic rheology or jamming transitions. These models arebased on the definition of an energy functional, which fully determines the cellu-lar response and conclusions. While two-dimensional vertex models have beenwidely employed, three-dimensional models are far more scarce, mainly due tothe large amount of configurations that they may adopt and the complex geomet-rical transitions they undergo. We hereinvestigate the shape of single and two-cells configurations as a function of the energy terms, and we study the depen-dence of the final shape on the model parameters: namely the exponent of theterm penalising cell-cell adhesion and surface contractility. In single cell analysis,we deduce analytically the radius and limit values of the contractility for linearand quadratic surface energy terms, in 2D and 3D. In two-cells systems, symmetri-cal and asymmetrical, we deduce the evolution of the aspect ratio and the relativeradius. While in functionals with linear surface terms yield the same aspect ratioin 2D and 3D, the configurations when usingquadratic surface terms are distinct.We relate our results with well-known solutions from capillarity theory, and verifyour analytical findings with a three-dimensional vertex model.
© 2023 The Authors. International Journal for Numerical Methods in Biomedical Engineering published by John Wiley & Sons Ltd.
2023-09-15T11:45:19Z
Khan, Ahmad Kamal
Muñoz Castro, Guillem
Muñoz Romero, José
Vertex models have been extensively used for simulating the evolution ofmulticellular systems, and have given rise to important global properties con-cerning their macroscopic rheology or jamming transitions. These models arebased on the definition of an energy functional, which fully determines the cellu-lar response and conclusions. While two-dimensional vertex models have beenwidely employed, three-dimensional models are far more scarce, mainly due tothe large amount of configurations that they may adopt and the complex geomet-rical transitions they undergo. We hereinvestigate the shape of single and two-cells configurations as a function of the energy terms, and we study the depen-dence of the final shape on the model parameters: namely the exponent of theterm penalising cell-cell adhesion and surface contractility. In single cell analysis,we deduce analytically the radius and limit values of the contractility for linearand quadratic surface energy terms, in 2D and 3D. In two-cells systems, symmetri-cal and asymmetrical, we deduce the evolution of the aspect ratio and the relativeradius. While in functionals with linear surface terms yield the same aspect ratioin 2D and 3D, the configurations when usingquadratic surface terms are distinct.We relate our results with well-known solutions from capillarity theory, and verifyour analytical findings with a three-dimensional vertex model.
On remote electronic voting with both coercion resistance and cast-as-intended verifiability
Finogina, Tamara
Herranz Sotoca, Javier
http://hdl.handle.net/2117/393548
2023-10-29T02:21:33Z
2023-09-15T10:56:03Z
On remote electronic voting with both coercion resistance and cast-as-intended verifiability
Finogina, Tamara; Herranz Sotoca, Javier
In this work, we study two essential but apparently contradictory properties of electronic voting systems: coercion resistance (CR) and cast-as-intended verifiability (CAI). Informally, the CR property ensures that a voter cannot prove to anybody else the vote content, which prevents vote selling and voting under duress. The CAI property ensures that a malicious voting device cannot cheat the voter and send to the ballot box an encryption of a voting option different from the one chosen by the voter.
In this work, we formalize security definitions capturing both coercion resistance and cast-as-intended verification in settings without secure delivery channels between the election authority and voters. After that, we consider some previously proposed solutions aimed at providing these two properties. For some of them (that we call unsatisfactory solutions) we show why they fail to achieve some of the two properties. We then concentrate on one of the two generic solutions that we call satisfactory: we prove that it satisfies the two proposed definitions and we detail how it can be instantiated in both classical cryptographic (e.g., ElGamal ciphertexts) and quantum-resistant (e.g., using lattice-based cryptosystems) settings.
2023-09-15T10:56:03Z
Finogina, Tamara
Herranz Sotoca, Javier
In this work, we study two essential but apparently contradictory properties of electronic voting systems: coercion resistance (CR) and cast-as-intended verifiability (CAI). Informally, the CR property ensures that a voter cannot prove to anybody else the vote content, which prevents vote selling and voting under duress. The CAI property ensures that a malicious voting device cannot cheat the voter and send to the ballot box an encryption of a voting option different from the one chosen by the voter.
In this work, we formalize security definitions capturing both coercion resistance and cast-as-intended verification in settings without secure delivery channels between the election authority and voters. After that, we consider some previously proposed solutions aimed at providing these two properties. For some of them (that we call unsatisfactory solutions) we show why they fail to achieve some of the two properties. We then concentrate on one of the two generic solutions that we call satisfactory: we prove that it satisfies the two proposed definitions and we detail how it can be instantiated in both classical cryptographic (e.g., ElGamal ciphertexts) and quantum-resistant (e.g., using lattice-based cryptosystems) settings.
On the Felsenthal power index
Freixas Bosch, Josep
Samaniego Vidal, Daniel
http://hdl.handle.net/2117/392589
2023-12-20T10:02:22Z
2023-07-31T11:19:11Z
On the Felsenthal power index
Freixas Bosch, Josep; Samaniego Vidal, Daniel
The paper that introduces the Felsenthal index is titled: ‘A well-behaved index of a priori P-Power for simple n-person games.’ In 2016, Felsenthal introduced his index for simple games. His definition does not base on the axiomatic approach. Then, Felsenthal regarded some properties and proved that his index satisfies a list of six reasonable and compelling postulates. Three of the properties that he regarded refer to the weighted games, but this fact does not reduce the definition of his index to weighted games. He proves that none of seven well-known efficient power indices proposed to date satisfies the list of postulates, indicating for each of them which of the six postulates violate. In this paper we extend some of his postulates, originally defined for weighted games, to simple games. The main objective of the article is to answer three open questions motivated in his article. In particular, we prove that his index may not be the unique one fulfilling the six proposed postulates, provide an axiomatic characterization for his index and, propose an impossibility result, which is obtained by adding a new postulate to a sublist of the postulates he considered. We also remark the existence of some alternative compelling postulates which are not satisfied for the index.
2023-07-31T11:19:11Z
Freixas Bosch, Josep
Samaniego Vidal, Daniel
The paper that introduces the Felsenthal index is titled: ‘A well-behaved index of a priori P-Power for simple n-person games.’ In 2016, Felsenthal introduced his index for simple games. His definition does not base on the axiomatic approach. Then, Felsenthal regarded some properties and proved that his index satisfies a list of six reasonable and compelling postulates. Three of the properties that he regarded refer to the weighted games, but this fact does not reduce the definition of his index to weighted games. He proves that none of seven well-known efficient power indices proposed to date satisfies the list of postulates, indicating for each of them which of the six postulates violate. In this paper we extend some of his postulates, originally defined for weighted games, to simple games. The main objective of the article is to answer three open questions motivated in his article. In particular, we prove that his index may not be the unique one fulfilling the six proposed postulates, provide an axiomatic characterization for his index and, propose an impossibility result, which is obtained by adding a new postulate to a sublist of the postulates he considered. We also remark the existence of some alternative compelling postulates which are not satisfied for the index.