5,369 research outputs found
Efficiently Learning from Revealed Preference
In this paper, we consider the revealed preferences problem from a learning
perspective. Every day, a price vector and a budget is drawn from an unknown
distribution, and a rational agent buys his most preferred bundle according to
some unknown utility function, subject to the given prices and budget
constraint. We wish not only to find a utility function which rationalizes a
finite set of observations, but to produce a hypothesis valuation function
which accurately predicts the behavior of the agent in the future. We give
efficient algorithms with polynomial sample-complexity for agents with linear
valuation functions, as well as for agents with linearly separable, concave
valuation functions with bounded second derivative.Comment: Extended abstract appears in WINE 201
Realizing lateral wrap-gated nanowire FETs: Controlling gate length with chemistry rather than lithography
An important consideration in miniaturizing transistors is maximizing the
coupling between the gate and the semiconductor channel. A nanowire with a
coaxial metal gate provides optimal gate-channel coupling, but has only been
realized for vertically oriented nanowire transistors. We report a method for
producing laterally oriented wrap-gated nanowire field-effect transistors that
provides exquisite control over the gate length via a single wet etch step,
eliminating the need for additional lithography beyond that required to define
the source/drain contacts and gate lead. It allows the contacts and nanowire
segments extending beyond the wrap-gate to be controlled independently by
biasing the doped substrate, significantly improving the sub-threshold
electrical characteristics. Our devices provide stronger, more symmetric gating
of the nanowire, operate at temperatures between 300 to 4 Kelvin, and offer new
opportunities in applications ranging from studies of one-dimensional quantum
transport through to chemical and biological sensing.Comment: 16 pages, 5 figures. Submitted version, published version available
at http://http://pubs.acs.org/journal/nalef
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Volatility term structures in commodity markets
In this study, we comprehensively examine the volatility term structures in commodity markets. We model state‐dependent spillovers in principal components (PCs) of the volatility term structures of different commodities, as well as that of the equity market. We detect strong economic links and a substantial interconnectedness of the volatility term structures of commodities. Accounting for intra‐commodity‐market spillovers significantly improves out‐of‐sample forecasts of the components of the volatility term structure. Spillovers following macroeconomic news announcements account for a large proportion of this forecast power. There thus seems to be substantial information transmission between different commodity markets
The Hall algebras of annuli
We refine and prove the central conjecture of our first paper for annuli with at least two marked intervals on each boundary component by computing the derived Hall algebras of their Fukaya categories
Activity Dependent Branching Ratios in Stocks, Solar X-ray Flux, and the Bak-Tang-Wiesenfeld Sandpile Model
We define an activity dependent branching ratio that allows comparison of
different time series . The branching ratio is defined as . The random variable is the value of the next signal given
that the previous one is equal to , so . If
, the process is on average supercritical when the signal is equal to
, while if , it is subcritical. For stock prices we find
within statistical uncertainty, for all , consistent with an ``efficient
market hypothesis''. For stock volumes, solar X-ray flux intensities, and the
Bak-Tang-Wiesenfeld (BTW) sandpile model, is supercritical for small
values of activity and subcritical for the largest ones, indicating a tendency
to return to a typical value. For stock volumes this tendency has an
approximate power law behavior. For solar X-ray flux and the BTW model, there
is a broad regime of activity where , which we interpret as an
indicator of critical behavior. This is true despite different underlying
probability distributions for , and for . For the BTW model the
distribution of is Gaussian, for sufficiently larger than one, and
its variance grows linearly with . Hence, the activity in the BTW model
obeys a central limit theorem when sampling over past histories. The broad
region of activity where is close to one disappears once bulk dissipation
is introduced in the BTW model -- supporting our hypothesis that it is an
indicator of criticality.Comment: 7 pages, 11 figure
Enhanced Zeeman splitting in Ga0.25In0.75As quantum point contacts
The strength of the Zeeman splitting induced by an applied magnetic field is
an important factor for the realization of spin-resolved transport in
mesoscopic devices. We measure the Zeeman splitting for a quantum point contact
etched into a Ga0.25In0.75As quantum well, with the field oriented parallel to
the transport direction. We observe an enhancement of the Lande g-factor from
|g*|=3.8 +/- 0.2 for the third subband to |g*|=5.8 +/- 0.6 for the first
subband, six times larger than in GaAs. We report subband spacings in excess of
10 meV, which facilitates quantum transport at higher temperatures.Comment: [Version 2] Revtex4, 11 pages, 3 figures, accepted for publication in
Applied Physics Letter
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