scholarly journals Parametric FIR Design of Propagation Loss Filters in Digital Waveguide String Models

2010 ◽  
Vol 17 (9) ◽  
pp. 795-798 ◽  
Author(s):  
Maarten van Walstijn
2021 ◽  
Vol 2021 (8) ◽  
Author(s):  
Anamaría Font ◽  
Bernardo Fraiman ◽  
Mariana Graña ◽  
Carmen A. Núñez ◽  
Héctor Parra De Freitas

Abstract Compactifications of the heterotic string on special Td/ℤ2 orbifolds realize a landscape of string models with 16 supercharges and a gauge group on the left-moving sector of reduced rank d + 8. The momenta of untwisted and twisted states span a lattice known as the Mikhailov lattice II(d), which is not self-dual for d > 1. By using computer algorithms which exploit the properties of lattice embeddings, we perform a systematic exploration of the moduli space for d ≤ 2, and give a list of maximally enhanced points where the U(1)d+8 enhances to a rank d + 8 non-Abelian gauge group. For d = 1, these groups are simply-laced and simply-connected, and in fact can be obtained from the Dynkin diagram of E10. For d = 2 there are also symplectic and doubly-connected groups. For the latter we find the precise form of their fundamental groups from embeddings of lattices into the dual of II(2). Our results easily generalize to d > 2.


2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Bilal Aghoutane ◽  
Mohammed El Ghzaoui ◽  
Hanan El Faylali

AbstractThe aim of this work consists in characterizing the Terahertz (THz) propagation channel in an indoor environment, in order to propose a channel model for THz bands. We first described a propagation loss model by taking into account the attenuation of the channel as a function of distance and frequency. The impulse response of the channel is then described by a set of rays, characterized by their amplitude, their delay and their phase. Apart from the frequency selective nature, path loss in THz band is also an others issue associated with THz communication systems. This work based on the conventional Saleh-Valenzuela (SV) model which is intended for indoor scenarios. In this paper, we have introduced random variables as Line of sight (LOS) component, and then merging it with the SV channel model to adopt it to the THz context. From simulation, we noted an important effect when the distance between the transmitter and the receiver change. This effect produces variations in frequency loss. The simulations carried out from this model show that to enhance the performance of THz system it is recommended to transmit information over transmission windows instead over the whole band.


2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Ivano Basile ◽  
Stefano Lanza

Abstract We study de Sitter configurations in ten-dimensional string models where supersymmetry is either absent or broken at the string scale. To this end, we derive expressions for the cosmological constant in general warped flux compactifications with localized sources, which yield no-go theorems that extend previous works on supersymmetric cases. We frame our results within a dimensional reduction and connect them to a number of Swampland conjectures, corroborating them further in the absence of supersymmetry. Furthermore, we construct a top-down string embedding of de Sitter brane-world cosmologies within unstable anti-de Sitter landscapes, providing a concrete realization of a recently revisited proposal.


1990 ◽  
Vol 56 (11) ◽  
pp. 990-992 ◽  
Author(s):  
M. Seto ◽  
A. Shahar ◽  
R. J. Deri ◽  
W. J. Tomlinson ◽  
A. Yi‐Yan

Author(s):  
C. Yamada ◽  
T. Nishimura ◽  
R. Yoshimura ◽  
H. Shimasaki ◽  
Y. Kado ◽  
...  
Keyword(s):  

2014 ◽  
Vol 11 (17) ◽  
pp. 20140707-20140707 ◽  
Author(s):  
Hiroki Ujihara ◽  
Neisei Hayashi ◽  
Marie Tabaru ◽  
Yosuke Mizuno ◽  
Kentaro Nakamura

2005 ◽  
Vol 20 (29) ◽  
pp. 7032-7034 ◽  
Author(s):  
T. S. YULDASHBAEV ◽  
KH. NURITDINOV

According to Pamir X-ray Emulsion Chamber (XEC) experimental data at the energies E est > 2 × 1016 eV the fraction of events with four "aligned" most energetic particles increases sharply for families without leading secondary particles. That energy dependence is not described by Quark Gluon String Models.


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