358 research outputs found
Modality, Potentiality and Contradiction in Quantum Mechanics
In [11], Newton da Costa together with the author of this paper argued in
favor of the possibility to consider quantum superpositions in terms of a
paraconsistent approach. We claimed that, even though most interpretations of
quantum mechanics (QM) attempt to escape contradictions, there are many hints
that indicate it could be worth while to engage in a research of this kind.
Recently, Arenhart and Krause [1, 2, 3] have raised several arguments against
this approach and claimed that, taking into account the square of opposition,
quantum superpositions are better understood in terms of contrariety
propositions rather than contradictory propositions. In [17] we defended the
Paraconsistent Approach to Quantum Superpositions (PAQS) and provided arguments
in favor of its development. In the present paper we attempt to analyze the
meanings of modality, potentiality and contradiction in QM, and provide further
arguments of why the PAQS is better suited, than the Contrariety Approach to
Quantum Superpositions (CAQS) proposed by Arenhart and Krause, to face the
interpretational questions that quantum technology is forcing us to consider.Comment: Published in: New Directions in Paraconsistent Logic, J-Y B\'eziau M.
Chakraborty & S. Dutta (Eds.), Springer, in press. arXiv admin note: text
overlap with arXiv:1404.518
Multiplexing Biochemical Signals
In this paper we show that living cells can multiplex biochemical signals,
i.e. transmit multiple signals through the same signaling pathway
simultaneously, and yet respond to them very specifically. We demonstrate how
two binary input signals can be encoded in the concentration of a common
signaling protein, which is then decoded such that each of the two output
signals provides reliable information about one corresponding input. Under
biologically relevant conditions the network can reach the maximum amount of
information that can be transmitted, which is 2 bits.Comment: 4 pages, 4 figure
Non-local signatures of the chiral magnetic effect in Dirac semimetal BiSb
The field of topological materials science has recently been focussing on
three-dimensional Dirac semimetals, which exhibit robust Dirac phases in the
bulk. However, the absence of characteristic surface states in accidental Dirac
semimetals (DSM) makes it difficult to experimentally verify claims about the
topological nature using commonly used surface-sensitive techniques. The chiral
magnetic effect (CME), which originates from the Weyl nodes, causes an
-dependent chiral charge polarization, which
manifests itself as negative magnetoresistance. We exploit the extended
lifetime of the chirally polarized charge and study the CME through both local
and non-local measurements in Hall bar structures fabricated from single
crystalline flakes of the DSM BiSb. From the non-local
measurement results we find a chiral charge relaxation time which is over one
order of magnitude larger than the Drude transport lifetime, underlining the
topological nature of BiSb.Comment: 6 pages, 6 figures + 7 pages of supplemental materia
Many worlds and modality in the interpretation of quantum mechanics: an algebraic approach
Many worlds interpretations (MWI) of quantum mechanics avoid the measurement
problem by considering every term in the quantum superposition as actual. A
seemingly opposed solution is proposed by modal interpretations (MI) which
state that quantum mechanics does not provide an account of what `actually is
the case', but rather deals with what `might be the case', i.e. with
possibilities. In this paper we provide an algebraic framework which allows us
to analyze in depth the modal aspects of MWI. Within our general formal scheme
we also provide a formal comparison between MWI and MI, in particular, we
provide a formal understanding of why --even though both interpretations share
the same formal structure-- MI fall pray of Kochen-Specker (KS) type
contradictions while MWI escape them.Comment: submitted to the Journal of Mathematical Physic
periodic Andreev bound states in a Dirac semimetal
Electrons in a Dirac semimetals possess linear dispersion in all three
spatial dimensions, and form part of a developing platform of novel quantum
materials. BiSb supports a three-dimensional Dirac cone at the
Sb-induced band inversion point. Nanoscale phase-sensitive junction technology
is used to induce superconductivity in this Dirac semimetal. Radio frequency
irradiation experiments reveal a significant contribution of 4-periodic
Andreev bound states to the supercurrent in Nb-BiSb-Nb
Josephson junctions. The conditions for a substantial contribution to
the supercurrent are favourable because of the Dirac cone's topological
protection against backscattering, providing very broad transmission
resonances. The large g-factor of the Zeeman effect from a magnetic field
applied in the plane of the junction, allows tuning of the Josephson junctions
from 0 to regimes.Comment: Supplementary information is include
Revisiting the Applicability of Metaphysical Identity in Quantum Mechanics
We discuss the hypothesis that the debate about the interpretation of the orthodox formalism of quantum mechanics might have been misguided right from the start by a biased metaphysical interpretation of the formalism and its inner mathematical relations. In particular, we focus on the orthodox interpretation of the congruence relation, '=', which relates equivalent classes of different mathematical representations of a vector in Hilbert
space, in terms of metaphysical identity. We will argue that this seemingly "common sense" interpretation, at the semantic level, has severe difficulties when considering the syntactic level of the theory
Carnot cycle for an oscillator
Carnot established in 1824 that the efficiency of cyclic engines operating
between a hot bath at absolute temperature and a bath at a lower
temperature cannot exceed . We show that linear
oscillators alternately in contact with hot and cold baths obey this principle
in the quantum as well as in the classical regime. The expression of the work
performed is derived from a simple prescription. Reversible and non-reversible
cycles are illustrated. The paper begins with historical considerations and is
essentially self-contained.Comment: 19 pages, 3 figures, sumitted to European Journal of Physics Changed
content: Fluctuations are considere
3-D focused inversion of near-seafloor magnetic data with application to the Brothers volcano hydrothermal system, Southern Pacific Ocean, New Zealand
Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 117 (2012): B10102, doi:10.1029/2012JB009349.We describe and apply a new inversion method for 3-D modeling of magnetic anomalies designed for general application but which is particularly useful for the interpretation of near-seafloor magnetic anomalies. The crust subsurface is modeled by a set of prismatic cells, each with uniform magnetization, that together reproduce the observed magnetic field. This problem is linear with respect to the magnetization, and the number of cells is normally greater than the amount of available data. Thus, the solution is obtained by solving an under-determined linear problem. A focused solution, exhibiting sharp boundaries between different magnetization domains, is obtained by allowing the amplitudes of magnetization to vary between a pre-determined range and by minimizing the region of the 3-D space where the source shows large variations, i.e., large gradients. A regularization functional based on a depth-weighting function is also introduced in order to counter-act the natural decay of the magnetic field intensity with depth. The inversion method has been used to explore the characteristics of the submarine hydrothermal system of Brothers volcano in the Kermadec arc, by inverting near-bottom magnetic data acquired by Autonomous Underwater Vehicles (AUVs). Different surface expressions of the hydrothermal vent fields show specific vertical structures in their underlying demagnetization regions that we interpret to represent hydrothermal upflow zones. For example, at focused vent sites the demagnetized conduits are vertical, pipe-like structures extending to depths of ~1000 m below the seafloor, whereas at diffuse vent sites the demagnetization regions are characterized by thin and inclined conduits.This contribution was made possible through funding by the New Zealand
Foundation for Research, Science and Technology (FRST contract
C05X0406) and by the Royal Society of New Zealand by the Marsden Fund
(grant GNS1003).2013-04-1
New Age and Geochemical Data from the Southern Colville and Kermadec Ridges, SW Pacific: Insights into the recent geological history and petrogenesis of the Proto-Kermadec (Vitiaz) Arc
Highlights
• Age and petrogenesis of the Miocene-Pleistocene proto Kermadec arc: the Kermadec and Colville Ridge
• Complex interplay between element flux from the subducting Pacific Plate and heterogenous mantle wedge
• New insights into the recent tectonic history of the Kermadec arc system
Abstract
The intra-oceanic Kermadec arc system extends ~1300 km between New Zealand and Fiji and comprises at least 30 arc front volcanoes, the Havre Trough back-arc and the remnant Colville and Kermadec Ridges. To date, most research has focussed on the Kermadec arc front volcanoes leaving the Colville and Kermadec Ridges virtually unexplored. Here, we present seven 40Ar/39Ar ages together with a comprehensive major and trace element and Sr-, Nd-, and Pb-isotope dataset from the Colville and Kermadec Ridges to better understand the evolution, petrogenesis and splitting of the former proto-Kermadec (Vitiaz) Arc to form these two remnant arc ridges. Our 40Ar/39Ar ages range from ~7.5–2.6 Ma, which suggests that arc volcanism at the Colville Ridge occurred continuously and longer than previously thought. Recovered Colville and Kermadec Ridge lavas range from mafic picro-basalts (MgO = ~8 wt%) to dacites. The lavas have arc-type normalised incompatible element patterns and Sr and Pb isotopic compositions intermediate between Pacific MORB and subducted lithosphere (including sediments, altered oceanic crust and serpentinised uppermost mantle). Geochemically diverse lavas, including ocean island basalt-like and potassic lavas with high Ce/Yb, Th/Zr, intermediate 206Pb/204Pb and low 143Nd/144Nd ratios were recovered from the Oligocene South Fiji Basin (and Eocene Three Kings Ridge) located west of the Colville Ridge. If largely trench-perpendicular mantle flow was operating during the Miocene, this geochemical heterogeneity was likely preserved in the Colville and Kermadec sub arc mantle. The Colville and Kermadec Ridge data therefore highlight the complex interplay between pre-existing mantle heterogeneities and material fluxes from the subducting Pacific Plate. The new data allow us to present a holistic (yet simplified) picture of the tectonic evolution of the late Vitiaz Arc and northern Zealandia since the Miocene and how this tectonism influences volcanic activity along the Kermadec arc at the present
A Topological Study of Contextuality and Modality in Quantum Mechanics
Kochen-Specker theorem rules out the non-contextual assignment of values to
physical magnitudes. Here we enrich the usual orthomodular structure of quantum
mechanical propositions with modal operators. This enlargement allows to refer
consistently to actual and possible properties of the system. By means of a
topological argument, more precisely in terms of the existence of sections of
sheaves, we give an extended version of Kochen-Specker theorem over this new
structure. This allows us to prove that contextuality remains a central feature
even in the enriched propositional system.Comment: 10 pages, no figures, submitted to I. J. Th. Phy
- …