2,887 research outputs found
Fast hashing with Strong Concentration Bounds
Previous work on tabulation hashing by Patrascu and Thorup from STOC'11 on
simple tabulation and from SODA'13 on twisted tabulation offered Chernoff-style
concentration bounds on hash based sums, e.g., the number of balls/keys hashing
to a given bin, but under some quite severe restrictions on the expected values
of these sums. The basic idea in tabulation hashing is to view a key as
consisting of characters, e.g., a 64-bit key as characters of
8-bits. The character domain should be small enough that character
tables of size fit in fast cache. The schemes then use tables
of this size, so the space of tabulation hashing is . However, the
concentration bounds by Patrascu and Thorup only apply if the expected sums are
.
To see the problem, consider the very simple case where we use tabulation
hashing to throw balls into bins and want to analyse the number of
balls in a given bin. With their concentration bounds, we are fine if ,
for then the expected value is . However, if , as when tossing
unbiased coins, the expected value is for large data sets,
e.g., data sets that do not fit in fast cache.
To handle expectations that go beyond the limits of our small space, we need
a much more advanced analysis of simple tabulation, plus a new tabulation
technique that we call \emph{tabulation-permutation} hashing which is at most
twice as slow as simple tabulation. No other hashing scheme of comparable speed
offers similar Chernoff-style concentration bounds.Comment: 54 pages, 3 figures. An extended abstract appeared at the 52nd Annual
ACM Symposium on Theory of Computing (STOC20
Network-aware design-space exploration of a power-efficient embedded application
The paper presents the design and multi-parameter optimization of a networked embedded application for the health-care domain. Several hardware, software, and application parameters, such as clock frequency, sensor sampling rate, data packet rate, are tuned at design- and run-time according to application specifications and operating conditions to optimize hardware requirements, packet loss, power consumption. Experimental results show that further power efficiency can be achieved by considering also communication aspects during design space exploratio
Carrier-envelope phase dependence in single-cycle laser pulse propagation with the inclusion of counter-rotating terms
We focus on the propagation properties of a single-cycle laser pulse through
a two-level medium by numerically solving the full-wave Maxwell-Bloch
equations. The counter-rotating terms in the spontaneous emission damping are
included such that the equations of motion are slightly different from the
conventional Bloch equations. The counter-rotating terms can considerably
suppress the broadening of the pulse envelope and the decrease of the group
velocity rooted from dispersion. Furthermore, for incident single-cycle pulses
with envelope area 4, the time-delay of the generated soliton pulse from
the main pulse depends crucially on the carrier-envelope phase of the incident
pulse. This can be utilized to determine the carrier-envelope phase of the
single-cycle laser pulse.Comment: 6 pages, 5 figure
Metabolism impacts upon Candida immunogenicity and pathogenicity at multiple levels
Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved. Open Access funded by Wellcome TrustNon peer reviewedPublisher PD
Measuring photon-photon interactions via photon detection
The strong non-linearity plays a significant role in physics, particularly,
in designing novel quantum sources of light and matter as well as in quantum
chemistry or quantum biology. In simple systems, the photon-photon interaction
can be determined analytically. However, it becomes challenging to obtain it
for more compex systems. Therefore, we show here how to measure strong
non-linearities via allowing the sample to interact with a weakly pumped
quantized leaking optical mode. We found that the detected mean-photon number
versus pump-field frequency shows several peaks. Interestingly, the interval
between neighbour peaks equals the photon-photon interaction potential.
Furthermore, the system exhibits sub-Poissonian photon statistics, entanglement
and photon switching with less than one photon. Finally, we connect our study
with existing related experiments.Comment: 4 pages, 3 figure
Asymptotic Stability for a Class of Metriplectic Systems
Using the framework of metriplectic systems on we will describe a
constructive geometric method to add a dissipation term to a Hamilton-Poisson
system such that any solution starting in a neighborhood of a nonlinear stable
equilibrium converges towards a certain invariant set. The dissipation term
depends only on the Hamiltonian function and the Casimir functions
Magnetic microscopy of topologically protected homochiral domain walls in an ultrathin perpendicularly magnetized Co film
Next-generation concepts for solid-state memory devices are based on
current-driven domain wall propagation, where the wall velocity governs the
device performance. It has been shown that the domain wall velocity and the
direction of travel is controlled by the nature of the wall and its chirality.
This chirality is attributed to effects emerging from the lack of inversion
symmetry at the interface between a ferromagnet and a heavy metal, leading to
an interfacial Dzyaloshinskii-Moriya interaction that can control the shape and
chirality of the magnetic domain wall. Here we present direct imaging of domain
walls in Pt/Co/AlO films using Lorentz transmission electron microscopy,
demonstrating the presence of homochiral, and thus topologically protected,
N\'{e}el walls. Such domain walls are good candidates for dense data storage,
bringing the bit size down close to the limit of the domain wall width
Nonholonomic Ricci Flows and Running Cosmological Constant: I. 4D Taub-NUT Metrics
In this work we construct and analyze exact solutions describing Ricci flows
and nonholonomic deformations of four dimensional (4D) Taub-NUT spacetimes. It
is outlined a new geometric techniques of constructing Ricci flow solutions.
Some conceptual issues on spacetimes provided with generic off-diagonal metrics
and associated nonlinear connection structures are analyzed. The limit from
gravity/Ricci flow models with nontrivial torsion to configurations with the
Levi-Civita connection is allowed in some specific physical circumstances by
constraining the class of integral varieties for the Einstein and Ricci flow
equations.Comment: latex2e, final variant to be published in IJMP
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