8,244 research outputs found
On the order of a non-abelian representation group of a slim dense near hexagon
We show that, if the representation group of a slim dense near hexagon
is non-abelian, then is of exponent 4 and ,
, where is the near polygon
embedding dimension of and is the dimension of the universal
representation module of . Further, if , then
is an extraspecial 2-group (Theorem 1.6)
On hyperovals of polar spaces
We derive lower and upper bounds for the size of a hyperoval of a finite polar space of rank 3. We give a computer-free proof for the uniqueness, up to isomorphism, of the hyperoval of size 126 of H(5, 4) and prove that the near hexagon E-3 has up to isomorphism a unique full embedding into the dual polar space DH(5, 4)
Introduction: Planetary memory in contemporary American fiction
This special issue considers the ways in which contemporary American fiction seeks to imagine a mode of ‘planetary memory’ able to address the scalar and systemic complexities of the Anthropocene – the epoch in which the combined activity of the human species has become a geological force in its own right. As Naomi Klein has recently argued, confronting the problem of anthropogenic climate change alters everything we know about the world: demanding wholesale recalibration of economic and political priorities; destabilising the epistemic frameworks through which quotidian life is interpreted and enacted; and decentring the dominant cultural imaginaries that seek to give form to historical experienc
Geometric Hyperplanes of the Near Hexagon L_3 times GQ(2, 2)
Having in mind their potential quantum physical applications, we classify all
geometric hyperplanes of the near hexagon that is a direct product of a line of
size three and the generalized quadrangle of order two. There are eight
different kinds of them, totalling to 1023 = 2^{10} - 1 = |PG(9, 2)|, and they
form two distinct families intricately related with the points and lines of the
Veldkamp space of the quadrangle in question.Comment: 10 pages, 5 figures and 2 tables; Version 2 - more detailed
discussion of the properties of hyperplane
CII* Absorption in Damped Lyman Alpha Systems: (II) A New Window on the Star Formation History of the Universe
Starting from the SFR per unit physical area, determined for DLAs using the C
II* method, we obtain the SFR per unit comoving volume at 3, and
find that it agrees with that for the Lyman Break Galaxies (LBGs). Though the
mass of produced stars indicated by the SFRs is consistent with the current
densities of known stellar populations, the mass of metals produced by =2.5
is 30 times larger than detected in absorption in DLAs. The most likely
solutions to this ``missing metals'' problem is that star formation occurs in
compact bulge regions. We search for evidence of feedback and find no
correlations between the SFR per unit area and N(H I), but possible
correlations between SFR per unit area and low-ion velocity width and SFR per
unit area and metal abundance. We show that (a) the correlation between cooling
rate and dust-to-gas ratio is positive evidence for grain photoelectric
heating, (b) the CMB does not significantly populate the C II excited
fine-structure states, and (c) the ratio of CII* to resonance-line optical
depths is a sensitive probe of the multi-phase structure of the DLA gas. We
address recent arguments that DLAs are comprised only of WNM gas, and show them
to be inconclusive. Despite the rough agreement between SFR per unit comoving
volume for DLAs and LBGs, current evidence indicates these are distinct
populations
Response of thin-film SQUIDs to applied fields and vortex fields: Linear SQUIDs
In this paper we analyze the properties of a dc SQUID when the London
penetration depth \lambda is larger than the superconducting film thickness d.
We present equations that govern the static behavior for arbitrary values of
\Lambda = \lambda^2/d relative to the linear dimensions of the SQUID. The
SQUID's critical current I_c depends upon the effective flux \Phi, the magnetic
flux through a contour surrounding the central hole plus a term proportional to
the line integral of the current density around this contour. While it is well
known that the SQUID inductance depends upon \Lambda, we show here that the
focusing of magnetic flux from applied fields and vortex-generated fields into
the central hole of the SQUID also depends upon \Lambda. We apply this
formalism to the simplest case of a linear SQUID of width 2w, consisting of a
coplanar pair of long superconducting strips of separation 2a, connected by two
small Josephson junctions to a superconducting current-input lead at one end
and by a superconducting lead at the other end. The central region of this
SQUID shares many properties with a superconducting coplanar stripline. We
calculate magnetic-field and current-density profiles, the inductance
(including both geometric and kinetic inductances), magnetic moments, and the
effective area as a function of \Lambda/w and a/w.Comment: 18 pages, 20 figures, revised for Phys. Rev. B, the main revisions
being to denote the effective flux by \Phi rather than
Quantum Monte Carlo Algorithm Based on Two-Body Density Functional Theory for Fermionic Many-Body Systems: Application to 3He
We construct a quantum Monte Carlo algorithm for interacting fermions using
the two-body density as the fundamental quantity. The central idea is mapping
the interacting fermionic system onto an auxiliary system of interacting
bosons. The correction term is approximated using correlated wave functions for
the interacting system, resulting in an effective potential that represents the
nodal surface. We calculate the properties of 3He and find good agreement with
experiment and with other theoretical work. In particular, our results for the
total energy agree well with other calculations where the same approximations
were implemented but the standard quantum Monte Carlo algorithm was usedComment: 4 pages, 3 figures, 1 tabl
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