Missing Elements and Missing Premises: A Combinatorial Argument for the Ontological Reduction of Chemistry

Does chemistry reduce to physics? If this means Can we derive the laws of chemistry from the laws of physics?', recent discussions suggest that the answer is no'. But sup posing that kind of reduction-- epistemological reduction'--to be impossible, the thesis of ontological reduction may still be true: that chemical properties are determined by more fundamental properties. However, even this thesis is threatened by some objections to the physicalist programme in the philosophy of mind, objections that generalize to the chemical case. Two objections are discussed: that physicalism is vacuous, and that nothing grounds the asymmetry of dependence which reductionism requires. Although it might seem rather surprising that the philosophy of chemistry is affected by shock waves from debates in the philosophy of mind, these objections show that there is an argumentative gap between, on the one hand, the theoretical connection linking chemical properties with properties at the sub-atomic level, and, on the other, the philosophical thesis of ontological reduction. The aim of this paper is to identify the missing premises (among them a theory of physical possibility) that would bridge this gap. Introduction: missing elements and the mystery of discreteness The refutation of physicalism A combinatorial theory of physical possibilia Combinatorialism and the Bohr model Objections The missing premises and a disanalogy with min

Time, and the static image

Photographs, paintings, rigid sculptures: all these provide examples of static images. It is true that they change-photographs fade,paintings darken and sculptures crumble-but what change they undergo (unless very damaging) is irrelevant to their representational content. A static image is one that represents by virtue of properties which remain largely unchanged throughout its existence. Because of this defining feature, according to a long tradition in aesthetics, a static image can only represent an instantaneous moment, or to be more exact the state of affairs obtaining at that moment'. It cannot represent movement and the passage of time. This traditional vieu- mirrors a much older one in metaphysics: that change is to be conceived of as a series of instantaneous states and hence that an interval of time is composed of extensionless moments. The metaphysical view has been involved in more controversy than its aesthetic counterpart. Aristotle identified it as one of the premises of Zeno's arrow paradoxZ and Augustine employed it in his proof of the unreality of time. The aesthetic view, for its part, was subjected to a blistering attack in Ernst Gombrich's brilliant essay 'Moment and movement in Art'", uhich persuasively argues, not only against the doctrine that the changeless cannot represent change, but also against the very idea of an instant of time. Still, Gombrich overstates his case. Is the idea of an instant simply a philosophers' fiction? And if we allow such an idea into our conception of the world, are we thereby committed to a mistaken view of pictorial representation? Implicit in Gombrich's argument is a link between depiction and perception. But what is this link, and what role does it play in the argument? I propose in this essay to take another look at the question of what time-span is represented by the static image, and consider whether answering this question presupposes a view of time and change. I shall begin with a brief resume of Gombrich's discussion

Space, supervenience and substantivalism

[FIRST PARAGRAPH] Consider a straight line on a flat surface running from point A to C and passing though B. Suppose the distance AB to be four inches, and the distance BC to be six inches. We can infer that the distance AC is ten inches. Of all geometrical inferences, this is surely one of the simplest. Of course, things are a little more complicated if the surface is not flat. If A, B and C are points on a sphere, then the shortest distance between A and C may be smaller (it may even be zero). We can make our inference immune from concerns about non-Euclidean spaces, however, by qualifying it as follows: if AB = n, and BC = m, then, in the direction A⇒B⇒C, the distance AC is n + m. This is apparently entirely trivial. But trivial truths can hide significant ontological ones. Let us translate our mathematical example to the physical world, and suppose A, B and C to be points, still in a straight line, but now at the centre of gravity of three physical objects

A puzzle concerning time perception

According to a plausible and influential account of perceptual knowledge, the truth-makers of beliefs that constitute perceptual knowledge must feature in the causal explanation of how we acquire those beliefs. However, this account runs into difficulties when it tries to accommodate time perception – specifically perception of order and duration – since the features we are apparently tracking in such perception are (it is argued) not causal. The central aim of the paper is to solve this epistemological puzzle. Two strategies are examined. The first strategy locates the causal truth-makers within the psychological mechanism underlying time perception, thus treating facts about time order and duration as mind-dependent. This strategy, however, is problematic. The second strategy modifies the causal account of perceptual knowledge to include a non-causal component in the explanation of belief-acquisition, namely chronometric explanation. Applying this much more satisfactory approach to perceptual knowledge of time, we can preserve the mind-independence of order and duration, but not that of time's flow

QUIJOTE Scientific Results. II. Polarisation Measurements of the Microwave Emission in the Galactic molecular complexes W43 and W47 and supernova remnant W44

We present Q-U-I JOint TEnerife (QUIJOTE) intensity and polarisation maps at 10-20 GHz covering a region along the Galactic plane 24<l<45 deg, |b|<8 deg. These maps result from 210 h of data, have a sensitivity in polarisation of ~40 muK/beam and an angular resolution of ~1 deg. Our intensity data are crucial to confirm the presence of anomalous microwave emission (AME) towards the two molecular complexes W43 (22 sigma) and W47 (8 sigma). We also detect at high significance (6 sigma) AME associated with W44, the first clear detection of this emission towards a SNR. The new QUIJOTE polarisation data, in combination with WMAP, are essential to: i) Determine the spectral index of the synchrotron emission in W44, beta_sync =-0.62 +/-0.03, in good agreement with the value inferred from the intensity spectrum once a free-free component is included in the fit. ii) Trace the change in the polarisation angle associated with Faraday rotation in the direction of W44 with rotation measure -404 +/- 49 rad/m2. And iii) set upper limits on the polarisation of W43 of Pi_AME <0.39 per cent (95 per cent C.L.) from QUIJOTE 17~GHz, and <0.22 per cent from WMAP 41 GHz data, which are the most stringent constraints ever obtained on the polarisation fraction of the AME. For typical physical conditions (grain temperature and magnetic field strengths), and in the case of perfect alignment between the grains and the magnetic field, the models of electric or magnetic dipole emissions predict higher polarisation fractions.Comment: Accepted for publication in MNRA

Comparison of Magnetic Field Structures on Different Scales in and around the Filamentary Dark Cloud GF 9

New visible polarization data combined with existing IR and FIR polarization data are used to study how the magnetic field threading the filamentary molecular cloud GF 9 connects to larger structures in its general environment. We find that when both visible and NIR polarization data are plotted as a function of extinction, there is no evidence for a plateau or a saturation effect in the polarization at Av ~ 1.3 as seen in dark clouds in Taurus. This lack of saturation effect suggests that even in the denser parts of GF 9 we are still probing the magnetic field. The visible polarization is smooth and has a well-defined orientation. The IR data are also well defined but with a different direction, and the FIR data in the core region are well defined and with yet another direction, but are randomly distributed in the filament region. On the scale of a few times the mean radial dimension of the molecular cloud, it is as if the magnetic field were `blind' to the spatial distribution of the filaments while on smaller scales within the cloud, in the core region near the IRAS point source PSC 20503+6006, polarimetry shows a rotation of the magnetic field lines in these denser phases. Hence, in spite of the fact that the spatial resolution is not the same in the visible/NIR and in the FIR data, all the data put together indicate that the field direction changes with the spatial scale. Finally, the Chandrasekhar and Fermi method is used to evaluate the magnetic field strength, indicating that the core region is approximately magnetically critical. A global interpretation of the results is that in the core region an original poloidal field could have been twisted by a rotating elongated (core+envelope) structure. There is no evidence for turbulence and ambipolar diffusion does not seem to be effective at the present time.Comment: 33 pages, 6 tables, 8 figures, Accepted by Ap

Comparison of prestellar core elongations and large-scale molecular cloud structures in the Lupus 1 region

Turbulence and magnetic fields are expected to be important for regulating molecular cloud formation and evolution. However, their effects on sub-parsec to 100 parsec scales, leading to the formation of starless cores, are not well understood. We investigate the prestellar core structure morphologies obtained from analysis of the Herschel-SPIRE 350 mum maps of the Lupus I cloud. This distribution is first compared on a statistical basis to the large-scale shape of the main filament. We find the distribution of the elongation position angle of the cores to be consistent with a random distribution, which means no specific orientation of the morphology of the cores is observed with respect to the mean orientation of the large-scale filament in Lupus I, nor relative to a large-scale bent filament model. This distribution is also compared to the mean orientation of the large-scale magnetic fields probed at 350 mum with the Balloon-borne Large Aperture Telescope for Polarimetry during its 2010 campaign. Here again we do not find any correlation between the core morphology distribution and the average orientation of the magnetic fields on parsec scales. Our main conclusion is that the local filament dynamics---including secondary filaments that often run orthogonally to the primary filament---and possibly small-scale variations in the local magnetic field direction, could be the dominant factors for explaining the final orientation of each core

Optical polarization and spectral properties of the H-poor superluminous supernovae SN 2021bnw and SN 2021fpl

New optical photometric, spectrocopic and imaging polarimetry data are combined with publicly available data to study some of the physical properties of the two H-poor superluminous supernovae (SLSN) SN 2021bnw and SN 2021fpl. For each SLSN, the best-fit parameters obtained from the magnetar model with \texttt{MOSFiT} do not depart from the range of parameter obtained on other SLSNe discussed in the literature. A spectral analysis with \texttt{SYN++} shows that SN 2021bnw is a W Type, Fast evolver, while SN 2021fpl is a 15bn Type, Slow evolver. The analysis of the polarimetry data obtained on SN 2021fpl at four epochs (+1.8, +20.6, +34.1 and +43.0 days, rest-frame) shows $> 3\sigma$ polarization detections in the range 0.8--1 $\%$. A comparison of the spectroscopy data suggests that SN 2021fpl underwent a spectral transition a bit earlier than SN 2015bn, during which, similarly, it could have underwent a polarization transition. The analysis of the polarimetry data obtained on SN 2021bnw do not show any departure from symmetry of the photosphere at an empirical diffusion timescale of $\approx$ 2 (+81.1 days rest-frame). This result is consistent with those on the sample of W Type SLSN observed at empirical diffusion timescale $\le$ 1 with that technique, even though it is not clear the effect of limited spectral windows varying from one object to the other. Measurements at higher empirical diffusion timescale may be needed to see any departure from symmetry as it is discussed in the literature for SN 2017egm.Comment: 29 pages, 13 Figures, 15 Tables, submitted to the MNRA

QUIJOTE scientific results - II. Polarisation measurements of the microwave emission in the Galactic molecular complexes W43 and W47 and supernova remnant W44

We present Q-U-I JOint TEnerife (QUIJOTE) intensity and polarisation maps at 10-20 GHz covering a region along the Galactic plane 24° ≳ l ≳ 45°, |b| ≳ 8°. These maps result from 210 h of data, have a sensitivity in polarisation of ≈ 40 μK beam and an angular resolution of ≈1°. Our intensity data are crucial to confirm the presence of anomalous microwave emission (AME) towards the two molecular complexesW43 (22σ) and W47 (8σ).We also detect at high significance (6σ) AME associated with W44, the first clear detection of this emission towards a supernova remnant. The new QUIJOTE polarisation data, in combination with Wilkinson Microwave Anisotropy Probe (WMAP), are essential to (i) determine the spectral index of the synchrotron emission in W44, β = -0.62 ± 0.03, in good agreement with the value inferred from the intensity spectrum once a free-free component is included in the fit; (ii) trace the change in the polarisation angle associated with Faraday rotation in the direction of W44 with rotation measure -404 ± 49 rad m and (iii) set upper limits on the polarisation ofW43 of Π < 0.39 per cent (95 per cent C.L.) from QUIJOTE 17 GHz, and < 0.22 per cent from WMAP 41 GHz data, which are the most stringent constraints ever obtained on the polarisation fraction of the AME. For typical physical conditions (grain temperature and magnetic field strengths), and in the case of perfect alignment between the grains and the magnetic field, the models of electric or magnetic dipole emissions predict higher polarisation fractions.This work has been partially funded by the Spanish Ministry of Economy and Competitiveness (MINECO) under the projects AYA2007-68058-C03-01, AYA2010-21766- C03-02, AYA2012-39475-C02-01, the Consolider-Ingenio project CSD2010-00064 (EPI: Exploring the Physics of Inflation) and also by the European Union’s Horizon 2020 research and innovation programme under grant agreement number 687312. FP thanks the European Commission under the Marie Sklodowska-Curie Actions within the H2020 program, Grant Agreement Number 658499-PolAME-H2020-MSCA-IF-2014.Peer Reviewe