133 research outputs found
Supersymmetric version of a hydrodynamic system in Riemann invariants and its solutions
In this paper, a supersymmetric extension of a system of hydrodynamic type
equations involving Riemann invariants is formulated in terms of a superspace
and superfield formalism. The symmetry properties of both the classical and
supersymmetric versions of this hydrodynamical model are analyzed through the
use of group-theoretical methods applied to partial differential equations
involving both bosonic and fermionic variables. More specifically, we compute
the Lie superalgebras of both models and perform classifications of their
respective subalgebras. A systematic use of the subalgebra structures allow us
to construct several classes of invariant solutions, including travelling
waves, centered waves and solutions involving monomials, exponentials and
radicals.Comment: 30 page
Obscurity and Gender Resistance in Patricia Duncker's James Miranda Barry
publication-status: Submittedtypes: Article© 2012 by Taylor & FrancisSince his death in 1865, military surgeon James Barry has alternately been classified as a
cross-dressing woman or as an intersexed individual. Patricia Duncker’s novel James
Miranda Barry (1999) poses an important challenge to such readings, as it does not
reveal any foundational truth about Barry’s sex. Resting on obscurity rather than
revelation, the text frustrates the desire to know the past in terms of gender binaries and
stable sexual identity categories. Drawing on feminist and queer theorisations of the
relation between gender and time, this essay demonstrates that Duncker’s use of obscurity
opens up alternative strategies of gender resistance.The Wellcome Trus
The Violence of the Canon: Revisiting Contemporary Notions of Canonical Forms
The historical conditions surrounding the processes of forming a canon are rarely examined directly, yet it is these processes which govern over the realm of religious representations and identity constructions. In light of recent critical scholarship, it is imperative to address theologically the role that the canon plays within a religious tradition. This essay demonstrates the cultural necessity of canonical forms despite their “monotheistic tendency” to subdivide the world into binary oppositions. By utilizing a scale of violence to determine the impact of the canonical form upon culture this essay offers an account of canons and their role in forming religious identities over and beyond the violence they are said to provoke. Through this clarification, an alternative perspective of canons can emerge that reveals the violence at the core of cultural-canonical norms, thus providing a valuable distinction between differing (violence-concealing or violence-revealing) canonical forms
Population density modifies the ecological impacts of invasive species
In assessments of ecological impact in invasion ecology, most studies compare un-invaded sites with highly invaded sites, representing the ‘worst-case scenario’, and so there is little information on how impact is modified by the population density of the invader. Here, we assess how ecological impact is modified by population density through the experimental development of density-impact curves for a model invasive fish. Using replicated mesocosms and the highly invasive Pseudorasbora parva as the model, we quantified how their population density influenced their diet composition and their impacts on invertebrate communities and ecosystem processes. The density-impact curves revealed both linear and non-linear density-impact relationships. The relationship between P. parva density and zooplankton body mass was represented by a low-threshold curve, where their impact was higher at low densities than predicted by a linear relationship. In contrast, whilst the relationship between density and zooplankton biomass and abundance was also non-linear, it was high-threshold, indicating a lower impact than a linear relationship would predict. Impacts on diversity and phytoplankton standing stock were linear and impacts on benthic invertebrate abundance and decomposition rates were represented by s-shaped curves. These relationships were underpinned by P. parva dietary analyses that revealed increasing reliance on zooplankton as density increased due to depletion of other resources. We caution against the common assumption that ecological impact increases linearly with invader density and suggest that increased understanding of the relationship between invader population density and ecological impact can avoid under-investment in the management of invaders that cause severe problems at low densities
The Nontriviality of Trivial General Covariance: How Electrons Restrict 'Time' Coordinates, Spinors (Almost) Fit into Tensor Calculus, and 7/16 of a Tetrad Is Surplus Structure
It is a commonplace that any theory can be written in any coordinates via
tensor calculus. But it is claimed that spinors as such cannot be represented
in coordinates in a curved space-time. What general covariance means for
theories with fermions is thus unclear. In fact both commonplaces are wrong.
Though it is not widely known, Ogievetsky and Polubarinov (OP) constructed
spinors in coordinates in 1965, helping to spawn nonlinear group
representations. Locally, these spinors resemble the orthonormal basis or
"tetrad" formalism in the symmetric gauge, but they are conceptually
self-sufficient. The tetrad formalism is de-Ockhamized, with 6 extra fields and
6 compensating gauge symmetries. OP spinors, as developed nonperturbatively by
Bilyalov, admit any coordinates at a point, but "time" must be listed first:
the product of the metric components and the matrix diag(-1,1,1,1) must have no
negative eigenvalues to yield a real symmetric square root function of the
metric. Thus the admissible coordinates depend on the types and values of the
fields. Apart from coordinate order and spinorial two-valuedness, OP spinors
form, with the metric, a nonlinear geometric object, with Lie and covariant
derivatives. Such spinors avoid a spurious absolute object in the
Anderson-Friedman analysis of substantive general covariance. They also permit
the gauge-invariant localization of the infinite-component gravitational energy
in GR. Density-weighted spinors exploit the conformal invariance of the
massless Dirac equation to show that the volume element is absent. Thus instead
of a matrix with 16 components, one can use weighted OP spinors coupled to the
9-component symmetric unimodular square root of the conformal metric density.
The surprising mildness of the restrictions on coordinates for the
Schwarzschild solution is exhibited. (edited)Comment: Forthcoming in \textit{Studies in History and Philosophy of Modern
Physics
The neutron and its role in cosmology and particle physics
Experiments with cold and ultracold neutrons have reached a level of
precision such that problems far beyond the scale of the present Standard Model
of particle physics become accessible to experimental investigation. Due to the
close links between particle physics and cosmology, these studies also permit a
deep look into the very first instances of our universe. First addressed in
this article, both in theory and experiment, is the problem of baryogenesis ...
The question how baryogenesis could have happened is open to experimental
tests, and it turns out that this problem can be curbed by the very stringent
limits on an electric dipole moment of the neutron, a quantity that also has
deep implications for particle physics. Then we discuss the recent spectacular
observation of neutron quantization in the earth's gravitational field and of
resonance transitions between such gravitational energy states. These
measurements, together with new evaluations of neutron scattering data, set new
constraints on deviations from Newton's gravitational law at the picometer
scale. Such deviations are predicted in modern theories with extra-dimensions
that propose unification of the Planck scale with the scale of the Standard
Model ... Another main topic is the weak-interaction parameters in various
fields of physics and astrophysics that must all be derived from measured
neutron decay data. Up to now, about 10 different neutron decay observables
have been measured, much more than needed in the electroweak Standard Model.
This allows various precise tests for new physics beyond the Standard Model,
competing with or surpassing similar tests at high-energy. The review ends with
a discussion of neutron and nuclear data required in the synthesis of the
elements during the "first three minutes" and later on in stellar
nucleosynthesis.Comment: 91 pages, 30 figures, accepted by Reviews of Modern Physic
Orientalism, Balkanism and Europe's Ottoman heritage
‘Orientalism’ has been used as a lens to understand consumption of heritage sites in non-Western contexts. Through the supplementary lens of ‘Balkanism’, we examine a European region with a significant heritage reflecting the c.500 year rule of the Ottoman Empire. Bosnia and Herzegovina, Republic of North Macedonia and Albania are selected for study given their concentration of Ottoman heritage sites. We note first that these countries' heritage tourism sectors anticipate and modify interpretation to accommodate ‘Western’ tourists' affectation of ‘surprise’ and ‘delight’ at a ‘remarkable’ crossroads between ‘West/East’ or ‘Christendom/Islam’. To understand why Ottoman heritage is often understood to be in but not of Europe, our analysis draws on scholarship interrogating ‘Europe's’ longstanding discursive erasure of its Ottoman-Islamic-Oriental ‘self’ and Tourism's role in this
Robust and persistent reactivation of SIV and HIV by N-803 and depletion of CD8+ cells
Human immunodeficiency virus (HIV) persists indefinitely in individuals with HIV who receive antiretroviral therapy (ART) owing to a reservoir of latently infected cells that contain replication-competent virus1–4. Here, to better understand the mechanisms responsible for latency persistence and reversal, we used the interleukin-15 superagonist N-803 in conjunction with the depletion of CD8+ lymphocytes in ART-treated macaques infected with simian immunodeficiency virus (SIV). Although N-803 alone did not reactivate virus production, its administration after the depletion of CD8+ lymphocytes in conjunction with ART treatment induced robust and persistent reactivation of the virus in vivo. We found viraemia of more than 60 copies per ml in all macaques (n = 14; 100%) and in 41 out of a total of 56 samples (73.2%) that were collected each week after N-803 administration. Notably, concordant results were obtained in ART-treated HIV-infected humanized mice. In addition, we observed that co-culture with CD8+ T cells blocked the in vitro latency-reversing effect of N-803 on primary human CD4+ T cells that were latently infected with HIV. These results advance our understanding of the mechanisms responsible for latency reversal and lentivirus reactivation during ART-suppressed infection
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