We discuss the production of two hadrons in e + e − annihilation within the framework of perturbative QCD. The cross section for this process is calculated to next-toleading order accuracy with a selection of variables that allows the consideration of events where the two hadrons are detected in the same jet. In this configuration we contemplate the possibility that the hadrons come from a double fragmentation of a single parton. The double-fragmentation functions required to describe the transition of a parton to two hadrons are also necessary to completely factorize all collinear singularities. We explicitly show that factorization applies to order α s in the case of two-hadron production. * Partially supported by Fundación Antorchas and CONICET.

Although the use of the word 'information', with different meanings, can be traced back to antique and medieval texts (see Adriaans 2013), it is only in the 20 th century that the term begins to acquire the present-day sense. Nevertheless, the pervasiveness of the notion of information both in our everyday life and in our scientific practice does not imply the agreement about the content of the concept. As Luciano Floridi (2010Floridi ( , 2011 stresses, it is a polysemantic concept associated with different phenomena, such as communication, knowledge, reference, meaning, truth, etc. In the second half of the 20 th century, philosophy begins to direct its attention to this omnipresent but intricate concept in an effort of unravel the tangle of significances surrounding it.According to a deeply rooted intuition, information is related with data, it has or carries content. In order to elucidate this idea, the philosophy of information has coined the concept of semantic information (Bar-Hillel and Carnap 1953, Bar-Hillel 1964, Floridi 2013, strongly related with notions such as reference, meaning and representation: semantic information has intentionality −"aboutness"−, it is directed to other things. On the other hand, in the field of science certain problems are expressed in terms of a notion of information amenable to quantification. At present, this mathematical perspective for understanding information is manifested in different formalisms, each corresponding to its own concept: Fisher information (which measures the dependence of a random variable X on an unknown parameter θ upon which the probability of X depends; see Fisher 1925), algorithmic information (which measures the length of the shortest program that produces a string on a universal Turing machine; see, e.g., Chaitin 1987), von Neumann entropy (which gives a measure of the quantum resources necessary to faithfully encode the state of the source-system; see Schumacher 1995), among others.Nevertheless, it is traditionally agreed that the seminal work for the mathematical view of information is the paper where Claude Shannon (1948) introduces a precise formalism designed to solve certain specific technological problems in communication engineering (see also Shannon 2 and Weaver 1949). Roughly speaking, Shannon entropy is concerned with the statistical properties of a given system and the correlations between the states of two systems, independently of the meaning and any semantic content of those states. Nowadays, Shannon's theory is a basic ingredient of the communication engineers training.At present, the philosophy of information has put on the table a number of open problems related with the concept of information (see Adriaans and van Benthem 2008): the possibility of unification of various theories of information, the question about a logic of information, the relations between information and thermodynamics, the meaning of quantum information, the links between information and computation, among others. In this wide panoply of open issues, it ca...

The word 'information' refers to a polysemantic concept associated with very different phenomena, such as communication, knowledge, reference and meaning (Floridi 2010(Floridi , 2011. In the discussions about this matter, the first distinction to be introduced is that between a semantic view, according to which information carries semantic content and, thus, is related to notions as reference and meaning, However, the problems of interpretation do not disappear even when the attention is restricted to a single formal concept (see Lombardi, Holik and Vanni 2014).During the last decades, new interpretive problems have arisen with the advent of quantum information, which combine the difficulties in the understanding of the concept of information with the well-known foundational puzzles derived from quantum mechanics itself. This situation contrasts with the huge development of the research field named 'quantum information', where new formal results multiply rapidly. In this context, the question 'What is quantum information?' is still far from having an answer on which the whole quantum information community agrees. In fact, the positions about the matter range from those who seem to deny the existence of quantum information (Duwell 2003), those who consider that it refers to information when it is encoded in quantum systems , and those who conceive it as a new kind of information absolutely different than Shannon information (Jozsa 1998;Brukner and Zeilinger 2001).In the present article we will address the question 'What is quantum information?' from a conceptual viewpoint. For this purpose, in Section 2 Schumacher's formalism is introduced by contrast with Shannon's theory. In Section 3 the definition of quantum information in terms of a quantum source is discussed. Section 4 is devoted to analyze the definition of information in terms of coding theorems. These tasks lead us to focus on the relationship between Shannon entropy and von Neumann entropy in Section 5, and to discuss the differences between the concepts of bit and

The so-called classical limit of quantum mechanics is generally studied in terms of the decoherence of the state operator that characterizes a system. This is not the only possible approach to decoherence. In previous works we have presented the possibility of studying the classical limit in terms of the decoherence of relevant observables of the system. On the basis of this approach, in this paper we introduce the classical limit from a logical perspective, by studying the way in which the logical structure of quantum properties corresponding to relevant observables acquires Boolean characteristics.

We present a formalism which allows one to define probabilities for expressions that involve properties at different times for classical and quantum systems and we study its lattice structure. The formalism is based on the notion of time translation of properties. In the quantum case, the properties involved should satisfy compatibility conditions in order to obtain well-defined probabilities. The formalism is applied to describe the double-slit experiment.