10,707 research outputs found
Non-geometric Kaluza-Klein monopoles and magnetic duals of M-theory R-flux backgrounds
We introduce a magnetic analogue of the seven-dimensional nonassociative
octonionic R-flux algebra that describes the phase space of M2-branes in
four-dimensional locally non-geometric M-theory backgrounds. We show that these
two algebras are related by a Spin(7) automorphism of the 3-algebra that
provides a covariant description of the eight-dimensional M-theory phase space.
We argue that this algebra also underlies the phase space of electrons probing
a smeared magnetic monopole in quantum gravity by showing that upon appropriate
contractions, the algebra reduces to the noncommutative algebra of a spin foam
model of three-dimensional quantum gravity, or to the nonassociative algebra of
electrons in a background of uniform magnetic charge. We realise this set-up in
M-theory as M-waves probing a delocalised Kaluza-Klein monopole, and show that
this system also has a seven-dimensional phase space. We suggest that the
smeared Kaluza-Klein monopole is non-geometric because it cannot be described
by a local metric. This is the magnetic analogue of the local non-geometry of
the R-flux background and arises because the smeared Kaluza-Klein monopole is
described by a U(1)-gerbe rather than a U(1)-fibration.Comment: 19 pages, 2 figures; v2: dimensionful factors corrected throughout,
exposition improved; Final version to be published in JHE
Comment on "Competition between helimagnetism and commensurate quantum spin correlations in LiCu2O2"
The microscopic origin of the recently observed helical structure in LiCu2O2
[1] is considered. It is shown that the frustrated antiferromagnetic double
chain scenario adopted in Ref.1 is unrealistic. It should be replaced by a
frustrated single-chain (CuO2) scenario proposed in Ref. 2 with ferromagnetic
nearest neighbor and antiferromagnetic next nearest neighbor exchange integrals
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[1] T. Masuda et al. Phys. Rev. Lett. 92 (2004), 177201. [2] A. Gippius et
al. Phys. Rev. B 70 (2004), R01426; cond-mat/0312576.Comment: one page, one figur
Towards Baselines for Shoulder Surfing on Mobile Authentication
Given the nature of mobile devices and unlock procedures, unlock
authentication is a prime target for credential leaking via shoulder surfing, a
form of an observation attack. While the research community has investigated
solutions to minimize or prevent the threat of shoulder surfing, our
understanding of how the attack performs on current systems is less well
studied. In this paper, we describe a large online experiment (n=1173) that
works towards establishing a baseline of shoulder surfing vulnerability for
current unlock authentication systems. Using controlled video recordings of a
victim entering in a set of 4- and 6-length PINs and Android unlock patterns on
different phones from different angles, we asked participants to act as
attackers, trying to determine the authentication input based on the
observation. We find that 6-digit PINs are the most elusive attacking surface
where a single observation leads to just 10.8% successful attacks, improving to
26.5\% with multiple observations. As a comparison, 6-length Android patterns,
with one observation, suffered 64.2% attack rate and 79.9% with multiple
observations. Removing feedback lines for patterns improves security from
35.3\% and 52.1\% for single and multiple observations, respectively. This
evidence, as well as other results related to hand position, phone size, and
observation angle, suggests the best and worst case scenarios related to
shoulder surfing vulnerability which can both help inform users to improve
their security choices, as well as establish baselines for researchers.Comment: Will appear in Annual Computer Security Applications Conference
(ACSAC
Automatic Classifiers for Medical Data from Doppler Unit
Nowadays, hand-held ultrasonic Doppler units are often used for noninvasive screening of atherosclerosis in arteries of the lower limbs. The mean velocity of blood flow in time and blood pressures are measured on several positions on each lower limb. This project presents software that is able to analyze such data and classify it in real time into selected diagnostic classes. It is also capable of giving a notice of some errors encountered during measuring. At the Department of Functional Diagnostics in the Regional Hospital of Liberec a database of several hundreds signals was collected. In cooperation with the specialist, the signals were manually classified into four classes. Consequently selected signal features were extracted and used for training a distance and a Bayesian classifier. Another set of signals was used for evaluating and optimizing the parameters of the classifiers. This paper compares the results of the software with those provided by a human expert. They agreed in 89 % cases
Intrinsic localized modes in the charge-transfer solid PtCl
We report a theoretical analysis of intrinsic localized modes in a
quasi-one-dimensional charge-transfer-solid (PtCl). We discuss strongly nonlinear features of resonant Raman
overtone scattering measurements on PtCl, arising from quantum intrinsic
localized (multiphonon) modes (ILMs) and ILM-plus-phonon states. We show, that
Raman scattering data displays clear signs of a non-thermalization of lattice
degrees-of-freedom, manifested in a nonequilibrium density of intrinsic
localized modes.Comment: 4 pages, 4 figures, REVTE
Development of a solid state thermostat final report
Solid state thermostat for space and airborne application
U-duality in three and four dimensions
Using generalised geometry we study the action of U-duality acting in three
and four dimensions on the bosonic fields of eleven dimensional supergravity.
We compare the U-duality symmetry with the T-duality symmetry of double field
theory and see how the and SL(5) U-duality groups reduce
to the SO(2,2) and SO(3,3) T-duality symmetry groups of the type IIA theory. As
examples we dualise M2-branes, both black and extreme. We find that uncharged
black M2-branes become charged under U-duality, generalising the Harrison
transformation, while extreme M2-branes will become new extreme M2-branes. The
resulting tension and charges are quantised appropriately if we use the
discrete U-duality group .Comment: v1: 35 pages; v2: minor corrections in section 4.1.2, many references
added; v3: further discussion added on the conformal factor of the
generalised metric in section 2 and on the Wick-rotation used to construct
examples in section
Kesediaan Pentadbir Awam Malaysia Menangani Globalisasi Dan Era E-Government
Malaysia liveliness wake Corridor region Raya Multimedia (Multimedia Super Corridor - MSC) has opened a new chapter to the development of the city. Get along or not Malaysia is no exception terheret together in globalization. Malaysia needs to be comparable to the developed countries so as not to lag behind in economic and technological development. Indeed, in order to achieve competitiveness in the global ranking high rate capability, along with the development of Putrajaya and Cyberjaya Bestari Bandaraya, electronics empire system has been implemented. The main Matlamat kingdom perlaksanaan electronic system is to deliver a system that cekap Pentadbiran kingdom, so that the impression can be competitive in the global rankings. However, the main cases that need to be woken up instead of our other systems, even cover human resource development lay administrators (e-governance) itself. Indeed, the issue essentially lay the extent of the willingness of administrators to handle the presence of systems electronics empire? Are there they are capable of in the aspect of human resource development such as a change in attitude and scientific (Humanware)? In connection with the issue-perseoalan dikemukan this paper will Membincang three major cases. The first is a theoretical discussion about the process of globalization, global society and the concept bandaraya bermaklumat bestari. Secondly, the discussion of the kingdom of electronic systems and the concept of ‘good governance' and the factors of human development. Third, during the discussion of keupayaan lay administrators in handling the system electronics empire
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