Relaxation times and ergodicity properties in a realistic ionic--crystal model, and the modern form of the FPU problem

It is well known that Gibbs' statistical mechanics is not justified for systems presenting long-range interactions, such as plasmas or galaxies. In a previous work we considered a realistic FPU-like model of an ionic crystal (and thus with long-range interactions), and showed that it reproduces the experimental infrared spectra from 1000 K down to 7 K, provided one abandons the Gibbs identification of temperature in terms of specific kinetic energy, at low temperatures. Here we investigate such a model in connection with its ergodicity properties. The conclusion we reach is that at low temperatures ergodicity does not occur, and thus the Gibbs prescriptions are not dynamically justified, up to geological time scales. We finally give a preliminary result indicating how the so-called `nonclassical' q-statistics show up in the realistic ionic-crystal model. How to formulate a consistent statistical mechanics, with the corresponding suitable identification of temperature in such nonergodicity conditions, remains an open problem, which apparently constitutes the modern form of the FPU problem

Bitcoin: a new Proof-of-Work system with reduced variance

Proof-of-Work (PoW) is a popular consensus protocol used by Bitcoin since its inception. PoW has the well-known flaw of assigning all the reward to the single miner (or pool) that inserts the new block. This has the consequence of making the variance of the reward and thus the mining enterprise risk extremely high. To address this problem, Shi in 2016 proposed a theoretical algorithm that would substantially reduce the issue. We introduce a variant of Proof-of-Work that improves on Shi's idea and can be easily implemented in practice. In order to insert a block, the network must not find a single nonce, but must find a few of them. This small change allows for a fairer distribution of rewards and at the same time has the effect of regularizing the insertion time of blocks. This would facilitate the emergence of small pools or autonomous miners

Automatically Drafting Ontologies from Competency Questions with FrODO

We present the Frame-based ontology Design Outlet (FrODO), a novel method and tool for drafting ontologies from competency questions automatically. Competency questions are expressed as natural language and are a common solution for representing requirements in a number of agile ontology engineering methodologies, such as the eXtreme Design (XD) or SAMOD. FrODO builds on top of FRED. In fact, it leverages the frame semantics for drawing domain-relevant boundaries around the RDF produced by FRED from a competency question, thus drafting domain ontologies. We carried out a user-based study for assessing FrODO in supporting engineers for ontology design tasks. The study shows that FrODO is effective in this and the resulting ontology drafts are qualitative.Comment: 15 page

Non-Interactive Commitment from Non-Transitive Group Actions

Group actions are becoming a viable option for post-quantum cryptography assumptions. Indeed, in recent years some works have shown how to construct primitives from assumptions based on isogenies of elliptic curves, such as CSIDH, on tensors or on code equivalence problems. This paper presents a bit commitment scheme, built on non-transitive group actions, which is shown to be secure in the standard model, under the decisional Group Action Inversion Problem. In particular, the commitment is computationally hiding and perfectly binding, and is obtained from a novel and general framework that exploits the properties of some orbit-invariant functions, together with group actions. Previous constructions depend on an interaction between the sender and the receiver in the commitment phase, which results in an interactive bit commitment. We instead propose the first non-interactive bit commitment based on group actions. Then we show that, when the sender is honest, the constructed commitment enjoys an additional feature, i.e., it is possible to tell whether two commitments were obtained from the same input, without revealing the input. We define the security properties that such a construction must satisfy, and we call this primitive linkable commitment. Finally, as an example, an instantiation of the scheme using tensors with coefficients in a finite field is provided. In this case, the invariant function is the computation of the rank of a tensor, and the cryptographic assumption is related to the Tensor Isomorphism problem

TRIFORS: LINKable Trilinear Forms Ring Signature

We present TRIFORS (TRIlinear FOrms Ring Signature), a logarithmic post-quantum (linkable) ring signature based on a novel assumption regarding the equivalence of alternating trilinear forms. The basis of this work is the construction by Beullens, Katsumata and Pintore from Asiacrypt 2020 to obtain a linkable ring signature from a cryptographic group action. The group action on trilinear forms used here is the same employed in the signature presented by Tang et al. at Eurocrypt 2022. We first define a sigma protocol that, given a set of public keys, the ring, allows to prove the knowledge of a secret key corresponding to a public one in the ring. Furthermore, some optimisations are used to reduce the size of the signature: among others, we use a novel application of the combinatorial number system to the space of the challenges. Using the Fiat-Shamir transform, we obtain a (linkable) ring signature of competitive length with the state-of-the-art among post-quantum proposals for security levels 128 and 192

Do altmetrics work for assessing research quality?

Alternative metrics (aka altmetrics) are gaining increasing interest in the scientometrics community as they can capture both the volume and quality of attention that a research work receives online. Nevertheless, there is limited knowledge about their effectiveness as a mean for measuring the impact of research if compared to traditional citation-based indicators. This work aims at rigorously investigating if any correlation exists among indicators, either traditional (i.e. citation count and h-index) or alternative (i.e. altmetrics) and which of them may be effective for evaluating scholars. The study is based on the analysis of real data coming from the National Scientific Qualification procedure held in Italy by committees of peers on behalf of the Italian Ministry of Education, Universities and Research