388 research outputs found
Addendum to "Nonlinear quantum evolution with maximal entropy production"
The author calls attention to previous work with related results, which has
escaped scrutiny before the publication of the article "Nonlinear quantum
evolution with maximal entropy production", Phys.Rev.A63, 022105 (2001).Comment: RevTex-latex2e, 2pgs., no figs.; brief report to appear in the May
2001 issue of Phys.Rev.
Deglaciation constraints in the Parâng Mountains, Southern Romania, using surface exposure dating
Cosmogenic nuclide surface exposure ages have been widely used to constrain glacial chronologies in the European regions. This paper brings new evidence that the Romanian Carpathians sheltered mountain glaciers in their upper valleys and cirques until the end of the last glaciation. Twenty-four 10Be surface exposure ages were obtained from boulders on moraine crests in the central area of the Parâng Mountains, Southern Carpathians. Exposure ages were used to constrain the timing of the deglaciation events during the Late Glacial. The lowest boulders yielded an age of 13.0 ± 1.1 (1766 m) and final deglaciation occurred at 10.2 ± 0.9 ka (2055 m). Timing of the Late Glacial events and complete deglaciation reported in this study are consistent with, and confirm, previously reported ages of deglaciation within the Carpathian and surrounding European region
WALLSY: The UWB and SmartMesh IP enabled Wireless Ad-hoc Low-power Localization SYstem
This paper follows the implementation of a proofof-concept localization system for GNSS-denied environments.
WALLSY (Wireless Ad-hoc Low-power Localization SYstem)
is a portable and modular Ultra Wide-Band (UWB) and Smart
Mesh IP (SMIP) hybrid. WALLSY uses UWB two way ranging
(TWR) to measure distances, which are then sent via the lowpower SMIP backbone network to a central hub for calculating
coordinates of tracked objects. The system is highly flexible and
requires no external infrastructure or prior knowledge of the
installation site. It uses a completely nomadic topology and
delivers high localization accuracy with all modules being
battery powered. It achieves this by using a custom time-slotting
protocol which maximizes deep-sleep mode for UWB. Battery
life can be further improved by activating inertial measurement
unit (IMU) filtering. Visualization of tracked objects and
system reconfiguration can be executed on-the-fly and are both
accessible to end users through a simple graphical user interface
(GUI). Results demonstrate that WALLSY can achieve more
than ten times longer battery lifetime compared to competing
solutions (localizing every 30 seconds). It provides 3D
coordinates with an average spatial error of 60.5cm and an
average standard deviation of 15cm. The system also provides
support for up to 20 tags
Off-Diagonal Deformations of Kerr Metrics and Black Ellipsoids in Heterotic Supergravity
Geometric methods for constructing exact solutions of motion equations with
first order corrections to the heterotic supergravity action
implying a non-trivial Yang-Mills sector and six dimensional, 6-d,
almost-K\"ahler internal spaces are studied. In 10-d spacetimes, general
parametrizations for generic off-diagonal metrics, nonlinear and linear
connections and matter sources, when the equations of motion decouple in very
general forms are considered. This allows us to construct a variety of exact
solutions when the coefficients of fundamental geometric/physical objects
depend on all higher dimensional spacetime coordinates via corresponding
classes of generating and integration functions, generalized effective sources
and integration constants. Such generalized solutions are determined by generic
off-diagonal metrics and nonlinear and/or linear connections. In particular, as
configurations which are warped/compactified to lower dimensions and for
Levi-Civita connections. The corresponding metrics can have (non) Killing
and/or Lie algebra symmetries and/or describe (1+2)-d and/or (1+3)-d domain
wall configurations, with possible warping nearly almost-K\"ahler manifolds,
with gravitational and gauge instantons for nonlinear vacuum configurations and
effective polarizations of cosmological and interaction constants encoding
string gravity effects. A series of examples of exact solutions describing
generic off-diagonal supergravity modifications to black hole/ ellipsoid and
solitonic configurations are provided and analyzed. We prove that it is
possible to reproduce the Kerr and other type black solutions in general
relativity (with certain types of string corrections) in 4-d and to generalize
the solutions to non-vacuum configurations in (super) gravity/ string theories.Comment: latex2e, 44 pages with table of content, v2 accepted to EJPC with
minor typos modifications requested by editor and referee and up-dated
reference
A Variational Procedure for Time-Dependent Processes
A simple variational Lagrangian is proposed for the time development of an
arbitrary density matrix, employing the "factorization" of the density. Only
the "kinetic energy" appears in the Lagrangian. The formalism applies to pure
and mixed state cases, the Navier-Stokes equations of hydrodynamics, transport
theory, etc. It recaptures the Least Dissipation Function condition of
Rayleigh-Onsager {\bf and in practical applications is flexible}. The
variational proposal is tested on a two level system interacting that is
subject, in one instance, to an interaction with a single oscillator and, in
another, that evolves in a dissipative mode.Comment: 25 pages, 4 figure
On the robustness of bucket brigade quantum RAM
We study the robustness of the bucket brigade quantum random access memory
model introduced by Giovannetti, Lloyd, and Maccone [Phys. Rev. Lett. 100,
160501 (2008)]. Due to a result of Regev and Schiff [ICALP '08 pp. 773], we
show that for a class of error models the error rate per gate in the bucket
brigade quantum memory has to be of order (where is the
size of the memory) whenever the memory is used as an oracle for the quantum
searching problem. We conjecture that this is the case for any realistic error
model that will be encountered in practice, and that for algorithms with
super-polynomially many oracle queries the error rate must be
super-polynomially small, which further motivates the need for quantum error
correction. By contrast, for algorithms such as matrix inversion [Phys. Rev.
Lett. 103, 150502 (2009)] or quantum machine learning [Phys. Rev. Lett. 113,
130503 (2014)] that only require a polynomial number of queries, the error rate
only needs to be polynomially small and quantum error correction may not be
required. We introduce a circuit model for the quantum bucket brigade
architecture and argue that quantum error correction for the circuit causes the
quantum bucket brigade architecture to lose its primary advantage of a small
number of "active" gates, since all components have to be actively error
corrected.Comment: Replaced with the published version. 13 pages, 9 figure
- …