8,560 research outputs found
Functorial properties of Putnam's homology theory for Smale spaces
We investigate functorial properties of Putnam's homology theory for Smale
spaces. Our analysis shows that the addition of a conjugacy condition is
necessary to ensure functoriality. Several examples are discussed that
elucidate the need for our additional hypotheses. Our second main result is a
natural generalization of Putnam's Pullback Lemma from shifts of finite type to
non-wandering Smale spaces.Comment: Updated to agree with published versio
Static and Dynamic Properties of Trapped Fermionic Tonks-Girardeau Gases
We investigate some exact static and dynamic properties of one-dimensional
fermionic Tonks-Girardeau gases in tight de Broglie waveguides with attractive
p-wave interactions induced by a Feshbach resonance. A closed form solution for
the one-body density matrix for harmonic trapping is analyzed in terms of its
natural orbitals, with the surprising result that for odd, but not for even,
numbers of fermions the maximally occupied natural orbital coincides with the
ground harmonic oscillator orbital and has the maximally allowed fermionic
occupancy of unity. The exact dynamics of the trapped gas following turnoff of
the p-wave interactions are explored.Comment: 4 pages, 2 figures, submitted to PR
Saddle Points and Stark Ladders: Exact Calculations of Exciton Spectra in Superlattices
A new, exact method for calculating excitonic absorption in superlattices is
described. It is used to obtain high resolution spectra showing the saddle
point exciton feature near the top of the miniband. The evolution of this
feature is followed through a series of structures with increasing miniband
width. The Stark ladder of peaks produced by an axial electric field is
investigated, and it is shown that for weak fields the line shapes are strongly
modified by coupling to continuum states, taking the form of Fano resonances.
The calculated spectra, when suitably broadened, are found to be in good
agreement with experimental results.Comment: 9 pages Revtex v3.0, followed by 4 uuencoded postscript figures,
SISSA-CM-94-00
Theory of spinor Fermi and Bose gases in tight atom waveguides
Divergence-free pseudopotentials for spatially even and odd-wave interactions
in spinor Fermi gases in tight atom waveguides are derived. The Fermi-Bose
mapping method is used to relate the effectively one-dimensional fermionic
many-body problem to that of a spinor Bose gas. Depending on the relative
magnitudes of the even and odd-wave interactions, the N-atom ground state may
have total spin S=0, S=N/2, and possibly also intermediate values, the case
S=N/2 applying near a p-wave Feshbach resonance, where the N-fermion ground
state is space-antisymmetric and spin-symmetric. In this case the fermionic
ground state maps to the spinless bosonic Lieb-Liniger gas. An external
magnetic field with a longitudinal gradient causes a Stern-Gerlach spatial
separation of the corresponding trapped Fermi gas with respect to various
values of .Comment: 4+ pages, 1 figure, revtex4. Submitted to PRA. Minor corrections of
typos and notatio
Coherence properties of the microcavity polariton condensate
A theoretical model is presented which explains the dominant decoherence
process in a microcavity polariton condensate. The mechanism which is invoked
is the effect of self-phase modulation, whereby interactions transform
polariton number fluctuations into random energy variations. The model shows
that the phase coherence decay, g1(t), has a Kubo form, which can be Gaussian
or exponential, depending on whether the number fluctuations are slow or fast.
This fluctuation rate also determines the decay time of the intensity
correlation function, g2(t), so it can be directly determined experimentally.
The model explains recent experimental measurements of a relatively fast
Gaussian decay for g1(t), but also predicts a regime, further above threshold,
where the decay is much slower.Comment: 5 pages, 1 figur
Media Coverage, Public Awareness and State Intervention in Child Abuse in China – An Analysis of High-Profile Cases
Abstract Key Practitioner Messages •Child abuse is a complex social problem that is often deeply rooted in the cultural, economic and social practices of the country in which it exists. •Child abuse in China is understood as deliberate and harmful acts, while many Western societies also include acts of omission such as neglect. •There is a complex relationship between public awareness, media coverage and state intervention
A direct proof of Kim's identities
As a by-product of a finite-size Bethe Ansatz calculation in statistical
mechanics, Doochul Kim has established, by an indirect route, three
mathematical identities rather similar to the conjugate modulus relations
satisfied by the elliptic theta constants. However, they contain factors like
and , instead of . We show here that
there is a fourth relation that naturally completes the set, in much the same
way that there are four relations for the four elliptic theta functions. We
derive all of them directly by proving and using a specialization of
Weierstrass' factorization theorem in complex variable theory.Comment: Latex, 6 pages, accepted by J. Physics
Evaluation of the Lewisham Trauma Informed Group Work Programme
This study is an evaluation of the Trauma Informed Group Work Programme developed by the Lewisham Youth Offending Service. It was commissioned by the London Borough of Lewisham with funding from the Youth Justice Board.
The Lewisham Trauma Informed Group Work Programme is an intervention that aims to reduce morbidity and mortality in under-18s due to violent assaults
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