2,785 research outputs found
Fubini vacua as a classical de Sitter vacua
The Fubini's idea to introduce a fundamental scale of hadron phenomena by
means of dilatation non-invariant vacuum state in the frame work of a scale
invariant Lagrangian field theory is recalled. The Fubini vacua is invariant
under the de Sitter subgroup of the full conformal group. We obtain a finite
entropy for the quantum state corresponding to the classical Fubini vacua in
Euclidean space-time resembeling the entropy of the de Sitter vacua. In
Minkowski space-time it is shown that the Fubini vacua is mainly a bath of
radiation with Rayleigh-Jeans distribution for the low energy radiation. In
four dimensions, the critical scalar theory is shown to be equivalent to the
Einstein field equation in the ansatz of conformally flat metrics and to the
SU(2) Yang-Mills theory in the 't Hooft ansatz. In D-dimensions, the Hitchin
formula for the information geometry metric of the moduli space of instantons
is used to obtain the information geometry of the free-parameter space of the
Fubini vacua which is shown to be a (D+1)-dimensional AdS space. Considering
the Fubini vacua as a de Sitter vacua, the corresponding cosmological constant
is shown to be given by the coupling constant of the critical scalar theory. In
Minkowski spacetime it is shown that the Fubini vacua is equivalent to an open
FRW universe.Comment: 15 pages, revtex4, to appear in Mod.Phys.Lett.
Filter Bank Multicarrier for Massive MIMO
This paper introduces filter bank multicarrier (FBMC) as a potential
candidate in the application of massive MIMO communication. It also points out
the advantages of FBMC over OFDM (orthogonal frequency division multiplexing)
in the application of massive MIMO. The absence of cyclic prefix in FBMC
increases the bandwidth efficiency. In addition, FBMC allows carrier
aggregation straightforwardly. Self-equalization, a property of FBMC in massive
MIMO that is introduced in this paper, has the impact of reducing (i)
complexity; (ii) sensitivity to carrier frequency offset (CFO); (iii)
peak-to-average power ratio (PAPR); (iv) system latency; and (v) increasing
bandwidth efficiency. The numerical results that corroborate these claims are
presented.Comment: 7 pages, 6 figure
Pilot Decontamination in CMT-based Massive MIMO Networks
Pilot contamination problem in massive MIMO networks operating in
time-division duplex (TDD) mode can limit their expected capacity to a great
extent. This paper addresses this problem in cosine modulated multitone (CMT)
based massive MIMO networks; taking advantage of their so-called blind
equalization property. We extend and apply the blind equalization technique
from single antenna case to multi-cellular massive MIMO systems and show that
it can remove the channel estimation errors (due to pilot contamination effect)
without any need for cooperation between different cells or transmission of
additional training information. Our numerical results advocate the efficacy of
the proposed blind technique in improving the channel estimation accuracy and
removal of the residual channel estimation errors caused by the users of the
other cells.Comment: Accepted in ISWCS 201
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