20,615 research outputs found
Modular Constraints on Superconformal Field Theories
We constrain the spectrum of and
superconformal field theories in two-dimensions by requiring the NS-NS sector
partition function to be invariant under the congruence
subgroup of the full modular group . We employ semi-definite
programming to find constraints on the allowed spectrum of operators with or
without charges. Especially, the upper bounds on the twist gap for the
non-current primaries exhibit interesting peaks, kinks, and plateau. We
identify a number of candidate rational (S)CFTs realized at the numerical
boundaries and find that they are realized as the solutions to modular
differential equations associated to . Some of the candidate
theories have been discussed by H\"ohn in the context of self-dual extremal
vertex operator (super)algebra. We also obtain bounds for the charged operators
and study their implications to the weak gravity conjecture in AdS.Comment: 50 pages, 16 figure
Modular Constraints on Conformal Field Theories with Currents
We study constraints coming from the modular invariance of the partition
function of two-dimensional conformal field theories. We constrain the spectrum
of CFTs in the presence of holomorphic and anti-holomorphic currents using the
semi-definite programming. In particular, we find the bounds on the twist gap
for the non-current primaries depend dramatically on the presence of
holomorphic currents, showing numerous kinks and peaks. Various rational CFTs
are realized at the numerical boundary of the twist gap, saturating the upper
limits on the degeneracies. Such theories include Wess-Zumino-Witten models for
the Deligne's exceptional series, the Monster CFT and the Baby Monster CFT. We
also study modular constraints imposed by -algebras of various
type and observe that the bounds on the gap depend on the choice of
-algebra in the small central charge region.Comment: 49 pages, 23 figure
A Design of MAC Model Based on the Separation of Duties and Data Coloring: DSDC-MAC
Among the access control methods for database security, there is Mandatory Access Control (MAC) model in which the security level is set to both the subject and the object to enhance the security control. Legacy MAC models have focused only on one thing, either confidentiality or integrity. Thus, it can cause collisions between security policies in supporting confidentiality and integrity simultaneously. In addition, they do not provide a granular security class policy of subjects and objects in terms of subjects\u27 roles or tasks. In this paper, we present the security policy of Bell_LaPadula Model (BLP) model and Biba model as one complemented policy. In addition, Duties Separation and Data Coloring (DSDC)-MAC model applying new data coloring security method is proposed to enable granular access control from the viewpoint of Segregation of Duty (SoD). The case study demonstrated that the proposed modeling work maintains the practicality through the design of Human Resources management System. The proposed model in this study is suitable for organizations like military forces or intelligence agencies where confidential information should be carefully handled. Furthermore, this model is expected to protect systems against malicious insiders and improve the confidentiality and integrity of data
Fabrication and tuning of plasmonic optical nanoantennas around droplet epitaxy quantum dots by cathodoluminescence
We use cathodoluminescence to locate droplet epitaxy quantum dots with a
precision nm before fabricating nanoantennas in their vicinity by
electron-beam lithography. Cathodoluminescence is further used to evidence the
effect of the antennas as a function of their length on the light emitted by
the dot. Experimental results are in good agreement with numerical simulations
of the structures
Decay dynamics and exciton localization in large GaAs quantum dots grown by droplet epitaxy
We investigate the optical emission and decay dynamics of excitons confined
in large strain-free GaAs quantum dots grown by droplet epitaxy. From
time-resolved measurements combined with a theoretical model we show that
droplet-epitaxy quantum dots have a quantum efficiency of about 75% and an
oscillator strength between 8 and 10. The quantum dots are found to be fully
described by a model for strongly-confined excitons, in contrast to the
theoretical prediction that excitons in large quantum dots exhibit the
so-called giant oscillator strength. We attribute these findings to localized
ground-state excitons in potential minima created by material intermixing
during growth. We provide further evidence for the strong-confinement regime of
excitons by extracting the size of electron and hole wavefunctions from the
phonon-broadened photoluminescence spectra. Furthermore, we explore the
temperature dependence of the decay dynamics and, for some quantum dots,
observe a pronounced reduction in the effective transition strength with
temperature. We quantify and explain these effects as being an intrinsic
property of large quantum dots owing to thermal excitation of the ground-state
exciton. Our results provide a detailed understanding of the optical properties
of large quantum dots in general, and of quantum dots grown by droplet epitaxy
in particular.Comment: 13 pages, 7 figure
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