21,111 research outputs found
Theories and Varying Fine Structure Constant
In analogy to theory, recently a new modified gravity theory, namely
the so-called theory, has been proposed to drive the current accelerated
expansion without invoking dark energy. In the present work, by extending
Bisabr's idea, we try to constrain theories with the varying fine
structure "constant", . We find that the constraints
on theories from the observational data are very
severe. In fact, they make theories almost indistinguishable from
CDM model.Comment: 12 pages, 4 figures, 1 table, revtex4; v2: discussions added, Phys.
Lett. B in press; v3: published versio
Neutron Density Distributions of Neutron-Rich Nuclei Studied with the Isobaric Yield Ratio Difference
The isobaric yield ratio difference (IBD) between two reactions of similar
experimental setups is found to be sensitive to nuclear density differences
between projectiles. In this article, the IBD probe is used to study the
density variation in neutron-rich Ca. By adjusting diffuseness in the
neutron density distribution, three different neutron density distributions of
Ca are obtained. The yields of fragments in the 80 MeV Ca
+ C reactions are calculated by using a modified statistical
abrasion-ablation model. It is found that the IBD results obtained from the
prefragments are sensitive to the density distribution of the projectile, while
the IBD results from the final fragments are less sensitive to the density
distribution of the projectile.Comment: 3 figure
Mixed numerologies interference analysis and inter-numerology interference cancellation for windowed OFDM systems
Extremely diverse service requirements are one of the critical challenges for the upcoming fifth-generation (5G) radio access technologies. As a solution, mixed numerologies transmission is proposed as a new radio air interface by assigning different numerologies to different subbands. However, coexistence of multiple numerologies induces the inter-numerology interference (INI), which deteriorates the system performance. In this paper, a theoretical model for INI is established for windowed orthogonal frequency division multiplexing (W-OFDM) systems. The analytical expression of the INI power is derived as a function of the channel frequency response of interfering subcarrier, the spectral distance separating the aggressor and the victim subcarrier, and the overlapping windows generated by the interferer's transmitter windows and the victim's receiver window. Based on the derived INI power expression, a novel INI cancellation scheme is proposed by dividing the INI into a dominant deterministic part and an equivalent noise part. A soft-output ordered successive interference cancellation (OSIC) algorithm is proposed to cancel the dominant interference, and the residual interference power is utilized as effective noise variance for the calculation of log-likelihood ratios (LLRs) for bits. Numerical analysis shows that the INI theoretical model matches the simulated results, and the proposed interference cancellation algorithm effectively mitigates the INI and outperforms the state-of-the-art W-OFDM receiver algorithms
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