Memory about the 14 th BWMC: SN P systems vs. ESN P systems with Transmittable States

The objectives of this memory are, on one hand, to provide a general overview about the topic of Membrane Computing, answering basic questions as what is it, which are its basic elements, which problems it allows to solve, its current limita- tions... and, on the other hand, to provide a more speci c information about the model of Spiking Neural P systems in both its original formulation and on the variant of the model suggested on the 14th edition of the Brainstorming Week on Membrane Computing, the Extended Spiking Neural P systems with Transmittable States. The motivation to further explore the topic of Spiking Neural P systems (SN P systems for short) comes from the idea that they could be a really suitable framework in order to model chain-reaction processes as the ssion of 235U taking place inside a nuclear reactor

Does inflation squeeze cosmological perturbations?

There seems to exist agreement about the fact that inflation squeezes the quantum state of cosmological perturbations and entangles modes with wavenumbers $\vec k$ and $-\vec k$. Paradoxically, this result has been used to justify both the classicality as well as the quantumness of the primordial perturbations at the end of inflation. We reexamine this question and point out that the definition of two-mode squeezing of the modes $\vec k$ and $-\vec k$ used in previous work rests on choices that are only justified for systems with time-independent Hamiltonians and finitely many degrees of freedom. We argue that for quantum fields propagating on generic time-dependent Friedmann-Lema\^itre-Robertson-Walker backgrounds, the notion of squeezed states is subject to ambiguities, which go hand in hand with the ambiguity in the definition of particles. In other words, we argue that the question "does the cosmic expansion squeeze and entangle modes with wavenumbers $\vec k$ and $-\vec k$?" contains the same ambiguity as the question "does the cosmic expansion create particles?". When additional symmetries are present, like in the (quasi) de Sitter-like spacetimes used in inflationary models, one can resolve the ambiguities, and we find that the answer to the question in the title turns out to be in the negative. We further argue that this fact does not make the state of cosmological perturbations any less quantum, at least when deviations from Gaussianity can be neglected.Comment: 19 pages + 8 pages as appendice

Stern-Gerlach Experiment

This work is about modelling an experiment composed by multiple Stern- Gerlach devices using Membrane Computing. We will study the behaviour of a set of independent particles passing through three linked Stern-Gerlach devices and discarting the spin down particles after passing through the first one, taking profit of the Membrane Computing’s ability of running parallel processing. Using a cell-like model to describe the system and testing it using the P-lingua framework we have obtained the theorically predicted results when the number of initial multisets is high enough

How ubiquitous is entanglement in quantum field theory?

It is well known that entanglement is widespread in quantum field theory, in the following sense: every Reeh-Schlieder state contains entanglement between any two spatially separated regions. This applies, in particular, to the vacuum of a non-interacting scalar theory in Minkowski spacetime. Discussions on entanglement in field theory have focused mainly on subsystems containing infinitely many degrees of freedom -- typically, the field modes that are supported within a compact region of space. In this article, we study entanglement in subsystems made of finitely many field degrees of freedom, in a free scalar theory in $D+1$-dimensional Minkowski spacetime. The focus on finitely many modes of the field is motivated by the finite capabilities of real experiments. We find that entanglement between finite-dimensional subsystems is {\em not common at all}, and that one needs to carefully select the support of modes for entanglement to show up. We also find that entanglement is increasingly sparser in higher dimensions. We conclude that entanglement in Minkowski spacetime is significantly less ubiquitous than normally thought.Comment: 25 pages, 19 figure

Interplay between [Delta] Particles and hyperons in neutron stars

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2018, Tutora: Àngels RamosWe analyze the effects of including [Delta](1232) isobars in an equation of state (EoS) forcold, [beta]-stable neutron star matter, employing Relativistic Nuclear Mean Field Theory. The selected EoS reproduces the properties of nuclear matter and finite nuclei, and also allows for the presence of hyperons in neutron stars having masses larger than 2M. We find that the composition and the structure of neutron stars are critically in uenced by the addition of the [delta]'s, an observation that allows us to constraint their interaction with the meson fields sigma and omega. Imposing that the EoS is stable and ensures the existence of 2M. neutron stars, as well as requiring agreement with data of [delta] excitation in nuclei, we find that, in the absence of other mechanisms stiffening the EoS at high densities, the interaction of the [delta]'s with the sigma and omega fields must be stronger than that of the nucleons

Uranium- decay chain

The main objective of this article is to modelize the process of decay of Uranium within the framework of Membrane Computing, so the evolution of great numbers of particles can be progressively followed and the results of the desintegrations (nuclei coming from and − decays) can be counted. In order to model the process in an accurate manner, exploiting the properties of maximal parallelism and non-determinism of Membrane Computing, a Population Dynamic P system (or PDP for short) restricted to one environment and a P system conformed by only the skin have been selected. The difficulty in the characterisation of this reactions lays in the simultaneity of the different decays, since the number of desintegrations of nucleous of each specie depend on the number of atoms of the initial population. In order to solve this problem and keep their attachment, the characteristic time of production of each decay has been translated into probabilities of deintregration of a nucleous using the decay constant

TDIS pressure profile simulations after LS2

During the LS2 (Long Shutdown 2), the current TDI (Beam Absorber for Injection) will be replaced by the new so called, TDIS (Beam Absorber for Injection Segmented). A throughout static/dynamic pressure profile validation in the concerned sectors is important for the upcoming beam operations. This document summarizes the outcome of the TDIS pressure profile simulations