A Sea Change in Eta Carinae

Major stellar-wind emission features in the spectrum of Eta Car have recently decreased by factors of order 2 relative to the continuum. This is unprecedented in the modern observational record. The simplest, but unproven, explanation is a rapid decrease in the wind density.Comment: 11 pages, 3 figures, accepted for publication in ApJ

Permutations and foster problems: two puzzles or one?

How are permutation arguments for the inscrutability of reference to be formulated in the context of a Davidsonian truth-theoretic semantics? Davidson (1979) takes these arguments to establish that there are no grounds for favouring a reference scheme that assigns London to ‘Londres’, rather than one that assigns Sydney to that name. We shall see, however, that it is far from clear whether permutation arguments work when set out in the context of the kind of truth-theoretic semantics which Davidson favours. The principle required to make the argument work allows us to resurrect Foster problems against the Davidsonian position. The Foster problems and the permutation inscrutability problems stand or fall together: they are one puzzle, not two

1-Hyperreflexivity and Complete Hyperreflexivity

The subspaces and subalgebras of B(H) which are hyperreflexive with constant 1 are completely classified. It is shown that there are 1-hyperreflexive subspaces for which the complete hyperreflexivity constant is strictly greater than 1. The constants for \bC T \otimes B(H) are analyzed in detail.Comment: 41 page

Finitely Correlated Representations of Product Systems of C∗C^*-Correspondences over Nk\mathbb{N}^k

We study isometric representations of product systems of correspondences over the semigroup $\mathbb{N}^k$ which are minimal dilations of finite dimensional, fully coisometric representations. We show the existence of a unique minimal cyclic coinvariant subspace for all such representations. The compression of the representation to this subspace is shown to be complete unitary invariant. For a certain class of graph algebras the nonself-adjoint \textsc{wot}-closed algebra generated by these representations is shown to contain the projection onto the minimal cyclic coinvariant subspace. This class includes free semigroup algebras. This result extends to a class of higher-rank graph algebras which includes higher-rank graphs with a single vertex.Comment: 34 pages; Introduction extended; to appear in the Journal of Functional Analysi

The trouble with ethnicity

The concept of exploitation is central to the Marxist understanding of history and contemporary society. But not all social conflicts can be immediately reduced to the struggle between exploiters and exploited, and to explain these conflicts we require other concepts. The most important is that of oppression. This refers to systematic discrimination by one social group against another on the grounds of characteristics either inherited (skin colour, gender) or socially acquired (religious belief, sexual orientation). The experience of oppression cuts across class lines, although that experience is more or less severe depending on where its victims are placed within the class structure. Some forms, like the oppression of women, have persisted throughout the existence of class society, while others, like racism, are specific to capitalism alone. Sometimes the reasons, or pretexts, for the oppression of a group may change over time. During the feudal era, for example, Jewish people were persecuted for their religious beliefs, but as capitalism developed persecution increasingly took place on the grounds of their supposed race. Whatever the reason or pretext, however, ruling classes throughout history have instigated or endorsed the oppression of different groups in order to maintain or create divisions amongst those over whom they rule. Recently, groups have increasingly been subjected to oppression on the grounds of their ethnicity. The most extreme form of such oppression has become known as 'ethnic cleansing'

Preparing for the Bomb: The Development of Civil Defence Policy in Canada, 1948–1963

During the period 1948 to 1963 civil defence in Canada developed in a number of stages that reflected changes in technology, weaponry and scientific discovery. The first stage of development, roughly between 1948 and 1952, witnessed only minor developments. Civil defence followed the Second World War practice, with a focus on air raid shelters and, if possible, evacuation. In the years 1952 to 1954 as the possibility of a nuclear attack became more real as a result of the Soviet development of intercontinental bombers, civil defence officials moved towards a policy of mass evacuation of target areas and the rescue of survivors. The detonation of a hydrogen bomb and the discovery of radioactive fallout in 1954 led to yet another change in civil defence plans. Civil defence officials became more convinced that mass evacuation of target areas was the answer, however, fallout shelters were also recommended for those areas outside the target area likely to be blanketed with radioactive debris. In the late 1950s and into the early 1960s civil defence again had to be redefined as intercontinental ballistic missiles (ICBMs) were developed and evacuation was no longer possible as nuclear attack could occur virtually without warning

Swine Feeding

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Axions: Bose Einstein Condensate or Classical Field?

The axion is a motivated dark matter candidate, so it would be interesting to find features in Large Scale Structures specific to axion dark matter. Such features were proposed for a Bose Einstein condensate of axions, leading to confusion in the literature (to which I contributed) about whether axions condense due to their gravitational interactions. This note argues that the Bose Einstein condensation of axions is a red herring: the axion dark matter produced by the misalignment mechanism is already a classical field, which has the distinctive features attributed to the axion condensate (BE condensates are described as classical fields). This note also estimates that the rate at which axion particles condense to the field, or the field evaporates to particles, is negligeable.Comment: 11 pages, 1 figure, version accepted for publicatio