Ontological indistinguishability as a central tenet of quantum theory.

Quantum indistinguishability directly relates to the philosophical debate on the notions of identity and individuality. They are crucial for our understanding of multipartite quantum systems. Furthermore, the correct interpretation of this feature of quantum theory has implications that transcend fundamental science and philosophy, given that quantum indistinguishability is a resource in quantum information theory. Most of the conceptual analysis of quantum indistinguishability is restricted to studying the permutational invariance of quantum states, the concomitant quantum statistics and their entanglement. Here, we analyse the role of indistinguishability and non-individuality in other areas of quantum theory. We start by analysing how a very peculiar use of indistinguishability underlies Feynman's rules for summing amplitudes in interference phenomena. Next, we study how quantum indistinguishability is underestimated in several topics of debate in the quantum physics literature, such as the Einstein-Podolsky-Rosen argument, Bell's inequalities and the Bell-Kochen-Specker theorem. Finally, we argue that an ontology of truly indistinguishable entities can serve as a basis for a quantum ontology that can give interesting answers to the interpretational problems of quantum mechanics. We claim that, in addition to superposition, contextuality and entanglement, indistinguishability (understood in a robust ontological sense) is one of the central features of quantum physics. This article is part of the theme issue 'Identity, individuality and indistinguishability in physics and mathematics'.

Comment on "Quantum Kaniadakis entropy under projective measurement".

We comment on the main result given by Ourabah et al. [Phys. Rev. E 92, 032114 (2015)PLEEE81539-375510.1103/PhysRevE.92.032114], noting that it can be derived as a special case of the more general study that we have provided in [Quantum Inf Process 15, 3393 (2016)10.1007/s11128-016-1329-5]. Our proof of the nondecreasing character under projective measurements of so-called generalized (h,ϕ) entropies (that comprise the Kaniadakis family as a particular case) has been based on majorization and Schur-concavity arguments. As a consequence, we have obtained that this property is obviously satisfied by Kaniadakis entropy but at the same time is fulfilled by all entropies preserving majorization. In addition, we have seen that our result holds for any bistochastic map, being a projective measurement a particular case. We argue here that looking at these facts from the point of view given in [Quantum Inf Process 15, 3393 (2016)10.1007/s11128-016-1329-5] not only simplifies the demonstrations but allows for a deeper understanding of the entropic properties involved.

[Roentgenological characteristic of pulmonary metastases in thyroid cancer in respect of its biological behaviour (author's transl)]. / Röntgenologische Charakteristik von Lungenmetastasen des Schilddrüsenkarzinoms mit Bezug auf sein biologisches Verhalten.

In metastases of the lung which must be considered as typical in cancer of the thyroid, it is possible to differentiate roentgenologically between fine and coarse nodules, the limit being approximately 10 mm. Metastases consisting of fine nodules are by no means to be considered as representing a fatal generalisation, whereas metastases with coarse nodules are frequently accompanied by other metastases distant from the primary tumour.

[Evaluation of the therapeutic and toxic action of platinum cis-dichlorodiamine]. / Otsenka terapevticheskogo i toksicheskogo deistviia tsis-dikhlordiamina platiny.

The substance under study was employed in 9 patients with a far-advanced lesion. Dosage of 7.5 mg/m2 of the body surface failed to render any effect, whereas 15 mg/m2 induced partial regression in 2 patients and stabilization of the process in another 2 patients. Some toxic phenomena were noted on the part of the digestive tract.