5,017 research outputs found
Noncommutative field theories on : Towards UV/IR mixing freedom
We consider the noncommutative space , a deformation of
the algebra of functions on which yields a "foliation" of
into fuzzy spheres. We first construct a natural matrix base
adapted to . We then apply this general framework to the
one-loop study of a two-parameter family of real-valued scalar noncommutative
field theories with quartic polynomial interaction, which becomes a non-local
matrix model when expressed in the above matrix base. The kinetic operator
involves a part related to dynamics on the fuzzy sphere supplemented by a term
reproducing radial dynamics. We then compute the planar and non-planar 1-loop
contributions to the 2-point correlation function. We find that these diagrams
are both finite in the matrix base. We find no singularity of IR type, which
signals very likely the absence of UV/IR mixing. We also consider the case of a
kinetic operator with only the radial part. We find that the resulting theory
is finite to all orders in perturbation expansion.Comment: 31 pages, 4 figures. Improved version. Sections 5.1 and 5.2 have been
clarified. A minor error corrected. References adde
SecMon: End-to-End Quality and Security Monitoring System
The Voice over Internet Protocol (VoIP) is becoming a more available and
popular way of communicating for Internet users. This also applies to
Peer-to-Peer (P2P) systems and merging these two have already proven to be
successful (e.g. Skype). Even the existing standards of VoIP provide an
assurance of security and Quality of Service (QoS), however, these features are
usually optional and supported by limited number of implementations. As a
result, the lack of mandatory and widely applicable QoS and security guaranties
makes the contemporary VoIP systems vulnerable to attacks and network
disturbances. In this paper we are facing these issues and propose the SecMon
system, which simultaneously provides a lightweight security mechanism and
improves quality parameters of the call. SecMon is intended specially for VoIP
service over P2P networks and its main advantage is that it provides
authentication, data integrity services, adaptive QoS and (D)DoS attack
detection. Moreover, the SecMon approach represents a low-bandwidth consumption
solution that is transparent to the users and possesses a self-organizing
capability. The above-mentioned features are accomplished mainly by utilizing
two information hiding techniques: digital audio watermarking and network
steganography. These techniques are used to create covert channels that serve
as transport channels for lightweight QoS measurement's results. Furthermore,
these metrics are aggregated in a reputation system that enables best route
path selection in the P2P network. The reputation system helps also to mitigate
(D)DoS attacks, maximize performance and increase transmission efficiency in
the network.Comment: Paper was presented at 7th international conference IBIZA 2008: On
Computer Science - Research And Applications, Poland, Kazimierz Dolny
31.01-2.02 2008; 14 pages, 5 figure
Molecular Signature of Polyoxometalates in Electron Transport of Silicon-based Molecular Junctions
Polyoxometalates (POMs) are unconventional electro-active molecules with a
great potential for applications in molecular memories, providing efficient
processing steps onto electrodes are available. The synthesis of the
organic-inorganic polyoxometalate hybrids
[PMO(Sn(CH)CC(CH)N)] (M = Mo,
W) endowed with a remote diazonium function is reported together with their
covalent immobilization onto hydrogenated n-Si(100) substrates. Electron
transport measurements through the resulting densely-packed monolayers
contacted with a mercury drop as a top electrode confirms their homogeneity.
Adjustment of the current-voltage curves with the Simmons equation gives a mean
tunnel energy barrier of 1.8 eV and 1.6 eV, for the Silicon-Molecules-Metal
(SMM) junctions based on the polyoxotungstates (M = W) and polyoxomolybdates (M
= Mo), respectively. This follows the trend observed in the electrochemical
properties of POMs in solution, the polyoxomolybdates being easier to reduce
than the polyoxotungstates, in agreement with lowest unoccupied molecular
orbitals (LUMOs) of lower energy. The molecular signature of the POMs is thus
clearly identifiable in the solid-state electrical properties and the unmatched
diversity of POM molecular and electronic structures should offer a great
modularity
Energy-efficient power allocation for point-to-point MIMO systems over the rayleigh fading channel
It is well-established that transmitting at full power is the most spectral-efficient power allocation strategy for point-to-point (P2P) multi-input multi-output (MIMO) systems, however, can this strategy be energy efficient as well? In this letter, we address the most energy-efficient power allocation policy for symmetric P2P MIMO systems by accurately approximating in closed-form their optimal transmit power when a realistic MIMO power consumption model is considered. In most cases, being energy efficient implies a reduction in transmit and overall consumed powers at the expense of a lower spectral efficiency
Quantum scale biomimicry of low dimensional growth: An unusual complex amorphous precursor route to TiO2 band confinement by shape adaptive biopolymer-like flexibility for energy applications
Crystallization via an amorphous pathway is often preferred by biologically driven processes enabling living species to better regulate activation energies to crystal formation that are intrinsically linked to shape and size of dynamically evolving morphologies. Templated ordering of 3-dimensional space around amorphous embedded non-equilibrium phases at heterogeneous polymer-metal interfaces signify important routes for the genesis of low-dimensional materials under stress-induced polymer confinement. We report the surface induced catalytic loss of P=O ligands to bond activated aromatization of C-C C=C and Ti=N resulting in confinement of porphyrin-TiO(2 )within polymer nanocages via particle attachment. Restricted growth nucleation of TiO2 to the quantum scale (Ë= 2 nm) is synthetically assisted by nitrogen, phosphine and hydrocarbon polymer chemistry via self-assembly. Here, the amorphous arrest phase of TiO, is reminiscent of biogenic amorphous crystal growth patterns and polymer coordination has both a chemical and biomimetic significance arising from quantum scale confinement which is atomically challenging. The relative ease in adaptability of non-equilibrium phases renders host structures more shape compliant to congruent guests increasing the possibility of geometrical confinement. Here, we provide evidence for synthetic biomimicry akin to bio-polymerization mechanisms to steer disorder-to-order transitions via solvent plasticization-like behaviour. This challenges the rationale of quantum driven confinement processes by conventional processes. Further, we show the change in optoelectronic properties under quantum confinement is intrinsically related to size that affects their optical absorption band energy range in DSSC.This work was supported by the National Research Foundation of Korea (NRF) grant funded by Korea government (MEST) NRF-2012R1A1A2008196, NRF 2012R1A2A2A01047189, NRF 2017R1A2B4008801, 2016R1D1A1A02936936, (NRF-2018R1A4A1059976, NRF-2018R1A2A1A13078704) and NRF Basic Research Programme in Science and Engineering by the Ministry of Education (No. 2017R1D1A1B03036226) and by the INDO-KOREA JNC program of the National Research Foundation of Korea Grant No. 2017K1A3A1A68. We thank BMSI (A*STAR) and NSCC for support. SJF is funded by grant IAF25 PPH17/01/a0/009 funded by A* STAR/NRF/EDB. CSV is the founder of a spinoff biotech Sinopsee Therapeutics. The current work has no conflicting interests with the company. We would like to express our very great appreciation to Ms. Hyoseon Kim for her technical expertise during HRTEM imaging
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