19,332 research outputs found
Hierarchical Role-Based Access Control with Homomorphic Encryption for Database as a Service
Database as a service provides services for accessing and managing customers
data which provides ease of access, and the cost is less for these services.
There is a possibility that the DBaaS service provider may not be trusted, and
data may be stored on untrusted server. The access control mechanism can
restrict users from unauthorized access, but in cloud environment access
control policies are more flexible. However, an attacker can gather sensitive
information for a malicious purpose by abusing the privileges as another user
and so database security is compromised. The other problems associated with the
DBaaS are to manage role hierarchy and secure session management for query
transaction in the database. In this paper, a role-based access control for the
multitenant database with role hierarchy is proposed. The query is granted with
least access privileges, and a session key is used for session management. The
proposed work protects data from privilege escalation and SQL injection. It
uses the partial homomorphic encryption (Paillier Encryption) for the
encrypting the sensitive data. If a query is to perform any operation on
sensitive data, then extra permissions are required for accessing sensitive
data. Data confidentiality and integrity are achieved using the role-based
access control with partial homomorphic encryption.Comment: 11 Pages,4 figures, Proceedings of International Conference on ICT
for Sustainable Developmen
Topological Origin of Zero-Energy Edge States in Particle-Hole Symmetric Systems
A criterion to determine the existence of zero-energy edge states is
discussed for a class of particle-hole symmetric Hamiltonians. A ``loop'' in a
parameter space is assigned for each one-dimensional bulk Hamiltonian, and its
topological properties, combined with the chiral symmetry, play an essential
role. It provides a unified framework to discuss zero-energy edge modes for
several systems such as fully gapped superconductors, two-dimensional d-wave
superconductors, and graphite ribbons. A variants of the Peierls instability
caused by the presence of edges is also discussed.Comment: Completely rewritten. Discussions on coexistence of is- or
id_{xy}-wave order parameter near edges in d_{x^{2}-y^{2}}-wave
superconductors are added; 4 pages, 3 figure
Boltzmann Suppression of Interacting Heavy Particles
Matsumoto and Yoshimura have recently argued that the number density of heavy
particles in a thermal bath is not necessarily Boltzmann-suppressed for T << M,
as power law corrections may emerge at higher orders in perturbation theory.
This fact might have important implications on the determination of WIMP relic
densities. On the other hand, the definition of number densities in a
interacting theory is not a straightforward procedure. It usually requires
renormalization of composite operators and operator mixing, which obscure the
physical interpretation of the computed thermal average. We propose a new
definition for the thermal average of a composite operator, which does not
require any new renormalization counterterm and is thus free from such
ambiguities. Applying this definition to the model of Matsumoto and Yoshimura
we find that it gives number densities which are Boltzmann-suppressed at any
order in perturbation theory. We discuss also heavy particles which are
unstable already at T=0, showing that power law corrections do in general
emerge in this case.Comment: 7 pages, 5 figures. New section added, with the discussion of the
case of an unstable heavy particle. Version to appear on Phys. Rev.
DIRBE Minus 2MASS: Confirming the CIRB in 40 New Regions at 2.2 and 3.5 Microns
With the release of the 2MASS All-Sky Point Source Catalog, stellar fluxes
from 2MASS are used to remove the contribution due to Galactic stars from the
intensity measured by DIRBE in 40 new regions in the North and South Galactic
polar caps. After subtracting the interplanetary and Galactic foregrounds, a
consistent residual intensity of 14.69 +/- 4.49 kJy/sr at 2.2 microns is found.
Allowing for a constant calibration factor between the DIRBE 3.5 microns and
the 2MASS 2.2 microns fluxes, a similar analysis leaves a residual intensity of
15.62 +/- 3.34 kJy/sr at 3.5 microns. The intercepts of the DIRBE minus 2MASS
correlation at 1.25 microns show more scatter and are a smaller fraction of the
foreground, leading to a still weak limit on the CIRB of 8.88 +/- 6.26 kJy/sr
(1 sigma).Comment: 25 pages LaTeX, 10 figures, 5 tables; Version accepted by the ApJ.
Includes minor changes to the text including further discussion of zodiacal
light issues and the allowance for variable stars in computing uncertainties
in the stellar contribution to the DIRBE intensitie
On Witten multiple zeta-functions associated with semisimple Lie algebras IV
In our previous work, we established the theory of multi-variable Witten
zeta-functions, which are called the zeta-functions of root systems. We have
already considered the cases of types , , , and . In
this paper, we consider the case of -type. We define certain analogues of
Bernoulli polynomials of -type and study the generating functions of them
to determine the coefficients of Witten's volume formulas of -type. Next
we consider the meromorphic continuation of the zeta-function of -type and
determine its possible singularities. Finally, by using our previous method, we
give explicit functional relations for them which include Witten's volume
formulas.Comment: 22 pag
Global Structure of Optically Thin, Magnetically Supported, Two-Temperature, Black Hole Accretion Disks
We present global solutions of optically thin, two-temperature black hole
accretion disks incorporating magnetic fields. We assume that the
{\pi}{\phi}-component of the Maxwell stress is proportional to the total
pressure, and prescribe the radial dependence of the magnetic flux advection
rate in order to complete the set of basic equations. We obtained magnetically
supported (low-{\beta}) disk solutions, whose luminosity exceeds the maximum
luminosity for an advection-dominated accretion flow (ADAF), L > 0.4 {\alpha}^2
L_Edd, where L_Edd is the Eddington luminosity. The accretion flow is composed
of the outer ADAF, a luminous hot accretion flow (LHAF) inside the transition
layer from the outer ADAF to the low-{\beta} disk, the low-{\beta} disk, and
the inner ADAF. The low-{\beta} disk region becomes wider as the mass-accretion
rate increases further. In the low-{\beta} disk, the magnetic heating balances
the radiative cooling, and the electron temperature decreases from ~ 10^9.5 K
to ~ 10^8 K as the luminosity increases. These results are consistent with the
anti-correlation between the energy cutoff in X-ray spectra (hence the electron
temperature) and the luminosity when L > 0.1 L_Edd, observed in the bright/hard
state during the bright hard-to-soft transitions of transient outbursts in
galactic black hole candidates.Comment: 27 pages, 15 figures, accepted for Publications of Astronomical
Society of Japa
Functional relations for zeta-functions of weight lattices of Lie groups of type
We study zeta-functions of weight lattices of compact connected semisimple
Lie groups of type . Actually we consider zeta-functions of SU(4), SO(6)
and PU(4), and give some functional relations and new classes of evaluation
formulas for them.Comment: 25 Page
Three-Dimensional Evolution of the Parker Instability under a Uniform Gravity
Using an isothermal MHD code, we have performed three-dimensional,
high-resolution simulations of the Parker instability. The initial equilibrium
system is composed of exponentially-decreasing isothermal gas and magnetic
field (along the azimuthal direction) under a uniform gravity. The evolution of
the instability can be divided into three phases: linear, nonlinear, and
relaxed. During the linear phase, the perturbations grow exponentially with a
preferred scale along the azimuthal direction but with smallest possible scale
along the radial direction, as predicted from linear analyses. During the
nonlinear phase, the growth of the instability is saturated and flow motion
becomes chaotic. Magnetic reconnection occurs, which allows gas to cross field
lines. This, in turn, results in the redistribution of gas and magnetic field.
The system approaches a new equilibrium in the relaxed phase, which is
different from the one seen in two-dimensional works. The structures formed
during the evolution are sheet-like or filamentary, whose shortest dimension is
radial. Their maximum density enhancement factor relative to the initial value
is less than 2. Since the radial dimension is too small and the density
enhancement is too low, it is difficult to regard the Parker instability alone
as a viable mechanism for the formation of giant molecular clouds.Comment: 8 pages of text, 4 figures (figure 2 in degraded gif format), to
appear in The Astrophysical Journal Letters, original quality figures
available via anonymous ftp at
ftp://ftp.msi.umn.edu/pub/users/twj/parker3d.uu or
ftp://canopus.chungnam.ac.kr/ryu/parker3d.u
Improvement of stabilizer based entanglement distillation protocols by encoding operators
This paper presents a method for enumerating all encoding operators in the
Clifford group for a given stabilizer. Furthermore, we classify encoding
operators into the equivalence classes such that EDPs (Entanglement
Distillation Protocol) constructed from encoding operators in the same
equivalence class have the same performance. By this classification, for a
given parameter, the number of candidates for good EDPs is significantly
reduced. As a result, we find the best EDP among EDPs constructed from [[4,2]]
stabilizer codes. This EDP has a better performance than previously known EDPs
over wide range of fidelity.Comment: 22 pages, 2 figures, In version 2, we enumerate all encoding
operators in the Clifford group, and fix the wrong classification of encoding
operators in version
- …