17,474 research outputs found
On compatibility between isogenies and polarisations of abelian varieties
We discuss the notion of polarised isogenies of abelian varieties, that is,
isogenies which are compatible with given principal polarisations. This is
motivated by problems of unlikely intersections in Shimura varieties. Our aim
is to show that certain questions about polarised isogenies can be reduced to
questions about unpolarised isogenies or vice versa.
Our main theorem concerns abelian varieties B which are isogenous to a fixed
abelian variety A. It establishes the existence of a polarised isogeny A to B
whose degree is polynomially bounded in n, if there exist both an unpolarised
isogeny A to B of degree n and a polarised isogeny A to B of unknown degree. As
a further result, we prove that given any two principally polarised abelian
varieties related by an unpolarised isogeny, there exists a polarised isogeny
between their fourth powers.
The proofs of both theorems involve calculations in the endomorphism algebras
of the abelian varieties, using the Albert classification of these endomorphism
algebras and the classification of Hermitian forms over division algebras
Clustering and Correlations at the Neutron Dripline
Some recent experimental studies of clustering and correlations within very
neutron-rich light nuclei are reviewed. In particular, the development of the
novel probes of neutron-neutron interferometry and Dalitz-plot analyses is
presented through the example of the dissociation of the two-neutron halo
system Be. The utility of high-energy proton radiative capture is
illustrated using a study of the He(p,) reaction. A new approach
to the production and detection of bound neutron clusters is also described,
and the observation of events with the characteristics expected for
tetraneutrons (n) liberated in the breakup of Be is discussed. The
prospects for future work, including systems beyond the neutron dripline, are
briefly outlined.Comment: Invited contribution to a topical issue on Exotic Nuclei of Les
Comptes Rendus de l'Academie des Sciences Paris, Serie IV. 29 pages,11
figures (format RevTex preprint
Space and place: writing encounters self
In addition to contributing this editorial article, Susan Orr and Claire Hind guest edited this issue
AXA General Insurance Ltd v Lord Advocate : analysis
Discusses the Supreme Court decision in AXA General Insurance Ltd, Petitioners on whether Scottish legislation which reversed a House of Lords ruling concerning the actionability of certain asbestos-related conditions breached insurers' rights
BeppoSAX observations of low-energy spectral features in AGN
The combination of the broad band coverage and moderate spectral resolution
of the LECS and MECS instruments on-board BeppoSAX allow the spectra of AGN to
be studied in unprecedented detail down to 0.1 keV. We describe the calibration
and the performance of the LECS and report on observations of low-energy
absorption features in the spectra of both a low (MCG-6-30-15) and a high
luminosity (3C 273) AGN. These features provide important diagnostics on the
location and nature of the material surrounding the AGN. A comparison of LECS
and ASCA/SIS low energy performance is also presented in the case of 3C 273.Comment: 5 pages. To appear in symposium proceedings: The Active X-Ray Sky,
Rome, October 199
Nonmodal energy growth and optimal perturbations in compressible plane Couette flow
Nonmodal transient growth studies and estimation of optimal perturbations
have been made for the compressible plane Couette flow with three-dimensional
disturbances. The maximum amplification of perturbation energy over time,
, is found to increase with increasing Reynolds number ,
but decreases with increasing Mach number . More specifically, the optimal
energy amplification (the supremum of over both the
streamwise and spanwise wavenumbers) is maximum in the incompressible limit and
decreases monotonically as increases. The corresponding optimal streamwise
wavenumber, , is non-zero at M=0, increases with increasing
, reaching a maximum for some value of and then decreases, eventually
becoming zero at high Mach numbers. While the pure streamwise vortices are the
optimal patterns at high Mach numbers, the modulated streamwise vortices are
the optimal patterns for low-to-moderate values of the Mach number. Unlike in
incompressible shear flows, the streamwise-independent modes in the present
flow do not follow the scaling law , the reasons
for which are shown to be tied to the dominance of some terms in the linear
stability operator. Based on a detailed nonmodal energy analysis, we show that
the transient energy growth occurs due to the transfer of energy from the mean
flow to perturbations via an inviscid {\it algebraic} instability. The decrease
of transient growth with increasing Mach number is also shown to be tied to the
decrease in the energy transferred from the mean flow () in
the same limit
ties that bind us
when objects converge in a space
they start a dialogue of their lives
lives that become entangled with your life
your memory
objects are the narrators of memory
a stain, a chip, a tear
materials embed meaning and metaphor within the process of creating
woven cloth, throwing lines, squeezed and pressed coils
all become remnants of the hand
as I make, play, and collect materials and objects
questions are brought forward
How do these components talk to one other?
What are they saying?
How do I listen?
knowledge is generated in the transformation of material through the process of
making with my hands.
a call and response
a conversation
an attentive listener / / an intuitive maker
I seek to excavate spaces and analyze my findings
in hope of contemplation and examination
a moment where my art becomes artifact
where the unfamiliar appears familiar
connecting materials and objects that have anchored our human experience
to ask the unanswerable questions of human existence
to love
to grieve
to grasp onto memories
to let go
to admire fate
to mourn
to gro
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