3,017 research outputs found
News and narratives in financial systems: Exploiting big data for systemic risk assessment
This paper applies algorithmic analysis to financial market text-based data to assess how narratives and sentiment might drive financial system developments. We find changes in emotional content in narratives are highly correlated across data sources and show the formation (and subsequent collapse) of exuberance prior to the global financial crisis. Our metrics also have predictive power for other commonly used indicators of sentiment and appear to influence economic variables. A novel machine learning application also points towards increasing consensus around the strongly positive narrative prior to the crisis. Together, our metrics might help to warn about impending financial system distress
The Breathing Modes of the Skyrmion and the Spin-Orbit Interaction
The coupling of the breathing and rotational modes of the skyrmion-skyrmion
system leads to a nucleon-nucleon spin-orbit interaction of short range, as
well as to spin-orbit potentials for the transitions , and . The longest range behaviour of these
spin-orbit potentials is calculated in closed form.Comment: Latex, figures not include
The middle Pleistocene transition by frequency locking and slow ramping of internal period
The increase in glacial cycle length from approximately to on average
thousand years around million years ago, called the Middle
Pleistocene Transition (MPT), lacks a conclusive explanation. We describe a
dynamical mechanism which we call Ramping with Frequency Locking (RFL), that
explains the transition by an interaction between the internal period of a
self-sustained oscillator and forcing that contains periodic components. This
mechanism naturally explains the abrupt increase in cycle length from
approximately to thousand years observed in proxy data, unlike some
previously proposed mechanisms for the MPT. A rapid increase in durations can
be produced by a rapid change in an external parameter, but this assumes rather
than explains the abruptness. In contrast, models relying on frequency locking
can produce a rapid change in durations assuming only a slow change in an
external parameter. We propose a scheme for detecting RFL in complex,
computationally expensive models, and motivate the search for climate variables
that can gradually increase the internal period of the glacial cycles.Comment: 14 pages, 12 figure
Tapered-amplified AR-coated laser diodes for Potassium and Rubidium atomic-physics experiments
We present a system of room-temperature extended-cavity grating-diode lasers
(ECDL) for production of light in the range 760-790nm. The extension of the
tuning range towards the blue is permitted by the weak feedback in the cavity:
the diodes are anti-reflection coated, and the grating has just 10%
reflectance. The light is then amplified using semiconductor tapered amplifiers
to give more than 400mW of power. The outputs are shown to be suitable for
atomic physics experiments with potassium (767nm), rubidium (780nm) or both, of
particular relevance to doubly-degenerate boson-fermion mixtures
Anomalous radio emission from dust in the Helix
A byproduct of experiments designed to map the CMB is the recent detection of
a new component of foreground Galactic emission. The anomalous foreground at ~
10--30 GHz, unexplained by traditional emission mechanisms, correlates with
100um dust emission. We report that in the Helix the emission at 31 GHz and
100um are well correlated, and exhibit similar features on sky images, which
are absent in H\beta. Upper limits on the 250 GHz continuum emission in the
Helix rule out cold grains as candidates for the 31 GHz emission, and provide
spectroscopic evidence for an excess at 31 GHz over bremsstrahlung. We estimate
that the 100um-correlated radio emission, presumably due to dust, accounts for
at least 20% of the 31 GHz emission in the Helix. This result strengthens
previous tentative interpretations of diffuse ISM spectra involving a new dust
emission mechanism at radio frequencies. Very small grains have not been
detected in the Helix, which hampers interpreting the new component in terms of
spinning dust. The observed iron depletion in the Helix favors considering the
identity of this new component to be magnetic dipole emission from hot
ferromagnetic grains. The reduced level of free-free continuum we report also
implies an electronic temperature of Te=4600\pm1200K for the free-free emitting
material, which is significantly lower than the temperature of 9500\pm500K
inferred from collisionally-excited lines (abridged).Comment: Accepted for publication in Ap
RESPOND â A patient-centred program to prevent secondary falls in older people presenting to the emergency department with a fall: Protocol for a multi-centre randomised controlled trial
Introduction: Participation in falls prevention activities by older people following presentation to the Emergency Department (ED) with a fall is suboptimal. This randomised controlled trial (RCT) will test the RESPOND program which is designed to improve older personsâ participation in falls prevention activities through delivery of patient-centred education and behaviour change strategies. Design and setting: An RCT at two tertiary referral EDs in Melbourne and Perth, Australia. Participants: Five-hundred and twenty eight community-dwelling people aged 60-90 years presenting to the ED with a fall and discharged home will be recruited. People who: require an interpreter or hands-on assistance to walk; live in residential aged care or >50 kilometres from the trial hospital; have terminal illness, cognitive impairment, documented aggressive behaviour or history of psychosis; are receiving palliative care; or are unable to use a telephone will be excluded. Methods: Participants will be randomly allocated to the RESPOND intervention or standard care control group. RESPOND incorporates: (1) home-based risk factor assessment; (2) education, coaching, goal setting, and follow-up telephone support for management of one or more of four risk factors with evidence of effective intervention; and (3) healthcare provider communication and community linkage delivered over six months. Primary outcomes are falls and fall injuries per-person-year. Discussion: RESPOND builds on prior falls prevention learnings and aims to help individuals make guided decisions about how they will manage their falls risk. Patient-centred models have been successfully trialled in chronic and cardiovascular disease however evidence to support this approach in falls prevention is limited. Trial registration. The protocol for this study is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12614000336684)
Nucleon form factors in the canonically quantized Skyrme model
The explicit expressions for the electric, magnetic, axial and induced
pseudoscalar form factors of the nucleons are derived in the {\it ab initio}
quantized Skyrme model. The canonical quantization procedure ensures the
existence of stable soliton solutions with good quantum numbers. The form
factors are derived for representations of arbitrary dimension of the SU(2)
group. After fixing the two parameters of the model, and , by the
empirical mass and electric mean square radius of the proton, the calculated
electric and magnetic form factors are fairly close to the empirical ones,
whereas the the axial and induced pseudoscalar form factors fall off too slowly
with momentum transfer.Comment: 14pp including figure
Correlated two-pion exchange and large-N(C) behavior of nuclear forces
The effect of correlated scalar-isoscalar two-pion exchange (CrTPE) modes is
considered in connection with central and spin-orbit parts of the NN force. The
two-pion correlation function is coupled directly to the scalar form factor of
the nucleon which we calculate in the large-N(C) limit where the nucleon can be
described as a soliton of an effective chiral theory. The results for the
central NN force show a strong repulsive core at short internucleon distances
supplemented by a moderate attraction beyond 1 fm. The long-range tail of the
central NN potential is driven by the the pion-nucleon sigma term and
consistent with the effective meson exchange. The spin-orbit part of
the NN potential is repulsive. The large-N(C) scaling behavior of the
scalar-isoscalar NN interaction is addressed. We show that the spin-orbit part
is O(1/N^2(C)) in strength relative to the central force resulting in the ratio
suggested by the 1/N(C) expansion for N(C)=3. The latter is in
agreement with our numerical analysis and with the Kaplan-Manohar large-N(C)
power counting. Unitarization of the scattering amplitude plays here
an important role and improves the tree level results. Analytical
representations of the CrTPE NN potential in terms of elementary functions are
derived and their chiral content is discussed.Comment: 29 pages, 7 figure
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