Shallow Analysis and the Slingshot Argument

According to the standard opinions in the literature, blocking the unacceptable consequences of the notorious slingshot argument requires imposing constraints on the metaphysics of facts or on theories of definite descriptions (or class abstracts). This paper argues that both of these well-known strategies to rebut the slingshot overshoot the mark. The slingshot, first and foremost, raises the question as to the adequate logical formalization of statements about facts, i.e. of factual contexts. It will be shown that a rigorous application of Quine's maxim of shallow analysis to formalizations of factual contexts paves the way for an account of formalizing such contexts which blocks the slingshot without ramifications for theories of facts or definite description

Causal Slingshots

Causal slingshots are formal arguments advanced by proponents of an event ontology of token-level causation which, in the end, are intended to show two things: (i) The logical form of statements expressing causal dependencies on token level features a binary predicate " causes ...” and (ii) that predicate takes events as arguments. Even though formalisms are only revealing with respect to the logical form of natural language statements, if the latter are shown to be adequately captured within a corresponding formalism, proponents of slingshots usually take the adequacy of their formalizations for granted without justifying it. The first part of this paper argues that the most discussed version of a causal slingshot, viz. the one e.g. presented by Davidson (Essays on actions and events. Oxford, Clarendon Press, 1980), can indeed be refuted for relying on an inadequate formal apparatus. In contrast, the formal means of Gödel's (The philosophy of Betrand Russell. New York, Tudor, 1944) often neglected slingshot are shown to stand on solid ground in the second part of the paper. Nonetheless, I contend that Gödel's slingshot does only half the work friends of event causation would like it to do. It provides good reasons for (i) but not for (ii

The Assembly and Merging History of Supermassive Black Holes in Hierarchical Models of Galaxy Formation

We assess models for the assembly of supermassive black holes (SMBHs) at the center of galaxies that trace their hierarchical build-up far up in the dark halo `merger tree'. We assume that the first `seed' black holes (BHs) formed in (mini)halos collapsing at z=20 from high-sigma density fluctuations. As these pregalactic holes become incorporated through a series of mergers into larger and larger halos, they sink to the center owing to dynamical friction, accrete a fraction of the gas in the merger remnant to become supermassive, form a binary system, and eventually coalesce. The merger history of dark matter halos and associated BHs is followed by cosmological Monte Carlo realizations of the merger hierarchy. A simple model, where quasar activity is driven by major mergers and SMBHs accrete at the Eddington rate a mass that scales with the fifth power of the velocity dispersion, is shown to reproduce the optical LF of quasars in the redshift range 1<z<4. Binary and triple BH interactions are followed in our merger tree. The assumptions underlying our scenario lead to the prediction of a population of massive BHs wandering in galaxy halos and the intergalactic medium at the present epoch, and contributing <10% to the total BH mass density. At all epochs the fraction of binary SMBHs in galaxy nuclei is of order 10%, while the fraction of binary quasars is less than 0.3%Comment: revised version, accepted for publication in the ApJ, emulateapj, 15 pages, 16 figure

Gödel's "slingshot" argument and his onto-theological system

The paper shows that it is possible to obtain a "slingshot" result in Gödel's theory of positiveness in the presence of the theorem of the necessary existence of God. In the context of the reconstruction of Gödel's original "slingshot" argument on the suppositions of non-Fregean logic, this is a natural result. The "slingshot" result occurs in sufficiently strong non-Fregean theories accepting the necessary existence of some entities. However, this feature of a Gödelian theory may be considered not as a trivialisation, but as an intended consequence of Gödel's ontotheological views

Recientes avances en metafísica: Categorías ontológicas y esquemas categoriales

[ES] Desde una perspectiva ontológica tradicional, y con la declarada intención de alejarse del relativismo contemporáneo, el presente escrito busca establecer algunos principios básicos para mantener la posición de la metafísica como el estudio sistemático de la realidad como un todo, y de la ontología como la ciencia del ser, sustentada en una teoría de categorías. Estas categorías están diferenciadas por las características distintivas de existencia e identidad de sus respectivos miembros, tomándose como «categorías ontológicas fundamentales» aquellas en donde sus miembros tienen condiciones para estas características de existencia e identidad que no sean especificables en una forma exhaustiva, en términos de dependencia ontológica, entre esos miembros y los miembros de otras categorías ontológicas. Este escrito hace entonces una revisión de las diferentes teorías de categorías ontológicas, y sus respectivas interpretaciones de cuántas y cuáles categorías deben ser reconocidas. [EN] From a traditional ontological perspective, and with the declared intention to move away from contemporary relativism, this paper aims to establish some basic principles to maintain the position of Metaphysics as the systematic study of reality as a whole, and Ontology as the science of being, based on a theory of categories. These categories are differentiated by the distinctive features of existence and identity of their respective members, taking as «fundamental ontological categories» those where its members have conditions for these characteristics of existence and identity that are not exhaustively specifiable, in terms of ontological dependence, between those members and members of other ontological categories. This paper then makes a revision of the different theories of ontological categories, and their respective interpretations of how many and which categories should be recognized

The Formation of the First Massive Black Holes

Supermassive black holes (SMBHs) are common in local galactic nuclei, and SMBHs as massive as several billion solar masses already exist at redshift z=6. These earliest SMBHs may grow by the combination of radiation-pressure-limited accretion and mergers of stellar-mass seed BHs, left behind by the first generation of metal-free stars, or may be formed by more rapid direct collapse of gas in rare special environments where dense gas can accumulate without first fragmenting into stars. This chapter offers a review of these two competing scenarios, as well as some more exotic alternative ideas. It also briefly discusses how the different models may be distinguished in the future by observations with JWST, (e)LISA and other instruments.Comment: 47 pages with 306 references; this review is a chapter in "The First Galaxies - Theoretical Predictions and Observational Clues", Springer Astrophysics and Space Science Library, Eds. T. Wiklind, V. Bromm & B. Mobasher, in pres

Multi-wavelength studies of non-magnetic cataclysmic variables

This thesis comprises spectroscopic case studies of three non-magnetic nova-like and dwarf nova type cataclysmic variables (CVs). The principal goals were to investigate the accretion disk and optical spectral line properties of a sample of CVs which are known (usually from ultraviolet studies) to drive a fast outflow or wind. New optical, time-series data sets, secured from La Palma and Canada, are used to establish the (often complex) time- and phase-dependent behaviour of the emission and absorption line sources. The optical analyses have also been compared and contrasted with constraints from Hubble Space Telescope (HST) and archive International Ultraviolet Explorer (IUE) data. High resolution optical spectroscopy of V795 Herculis is presented. Separate low and high velocity fluctuations phased on the 2.6 hr orbital period are observed in the Balmer lines. This thesis argues against models which invoke channelled accretion columns flowing onto a synchronously rotating white dwarf, instead presenting disk-overflow model simulations which quantitatively account for several of the observed dynamical properties of V795 Her. The discrepancies of this model are addressed. A comparison of these optical spectra to quasi-simultaneous HST observations (which provide an unprecedented multi-wavelength data set) is made. A strong correlation between the overall UV and optical line strength changes implies that the UV changes cannot be principally due to the fast outflow. A time-resolved orbital study of the dwarf nova SS Cygni is also presented. These observations were taken at the maximum of a long, asymmetric type outburst, and confirm the presence of stationary, low velocity emission previously reported during a long, symmetric outburst. Possible sources for this emission, including a wind origin, are investigated. The peculiar nova-like BZ Camelopardalis, associated with a bow-shock nebula, has previously shown unambiguous evidence for a wind in its optical spectrum. New optical data reveal wind-formed features in the Balmer lines. Model fits constrain the inclination angle and archive IUE spectra are used to estimate the wind mass loss

An Energetic AGN Outburst Powered by a Rapidly Spinning Supermassive Black Hole or an Accreting Ultramassive Black Hole

Powering the 10^62 erg nuclear outburst in the MS0735.6+7421 cluster central galaxy by accretion implies that its supermassive black hole (SMBH) grew by ~6x10^8 solar masses over the past 100 Myr. We place upper limits on the amount of cold gas and star formation near the nucleus of <10^9 solar masses and <2 solar masses per year, respectively. These limits imply that an implausibly large fraction of the preexisting cold gas in the bulge must have been consumed by its SMBH at the rate of ~3-5 solar masses per year while leaving no trace of star formation. Such a high accretion rate would be difficult to maintain by stellar accretion or the Bondi mechanism, unless the black hole mass approaches 10^11 solar masses. Its feeble nuclear luminosities in the UV, I, and X-ray bands compared to its enormous mechanical power are inconsistent with rapid accretion onto a ~5x10^9 solar mass black hole. We suggest instead that the AGN outburst is powered by a rapidly-spinning black hole. A maximally-spinning, 10^9 solar mass black hole contains enough rotational energy, ~10^62 erg, to quench a cooling flow over its lifetime and to contribute significantly to the excess entropy found in the hot atmospheres of groups and clusters. Two modes of AGN feedback may be quenching star formation in elliptical galaxies centered in cooling halos at late times. An accretion mode that operates in gas-rich systems, and a spin mode operating at modest accretion rates. The spin conjecture may be avoided in MS0735 by appealing to Bondi accretion onto a central black hole whose mass greatly exceeds 10^10 solar mass. The host galaxy's unusually large, 3.8 kpc stellar core radius (light deficit) may witness the presence of an ultramassive black hole.Comment: Accepted for publication in ApJ. Modifications: adopted slightly higher black hole mass using Lauer's M_SMBH vs L_bulge relation and adjusted related quantities; considered more seriously the consequences of a ultramassive black hole, motivated by new Kormendy & Bender paper published after our submission; other modifications per referee comments by Ruszkowsk