The Neutrino Mass Window for Baryogenesis

Interactions of heavy Majorana neutrinos in the thermal phase of the early universe may be the origin of the cosmological matter-antimatter asymmetry. This mechanism of baryogenesis implies stringent constraints on light and heavy Majorana neutrino masses. We derive an improved upper bound on the CP asymmetry in heavy neutrino decays which, together with the kinetic equations, yields an upper bound on all light neutrino masses of 0.1 eV. Lepton number changing processes at temperatures above the temperature T_B of baryogenesis can erase other, pre-existing contributions to the baryon asymmetry. We find that these washout processes become very efficient if the effective neutrino mass \tilde{m}_1 is larger than m_* \simeq 10^{-3} eV. All memory of the initial conditions is then erased. Hence, for neutrino masses in the range from (\Delta m^2_sol)^{1/2} \simeq 8*10^{-3} eV to (\Delta m^2_atm)^{1/2} \simeq 5*10^{-2} eV, which is suggested by neutrino oscillations, leptogenesis emerges as the unique source of the cosmological matter-antimatter asymmetry.Comment: 29 pages, 12 figures include

Some Aspects of Thermal Leptogenesis

Properties of neutrinos may be the origin of the matter-antimatter asymmetry of the universe. In the seesaw model for neutrino masses this leads to important constraints on the properties of light and heavy neutrinos. In particular, an upper bound on the light neutrino masses of 0.1 eV can be derived. We review the present status of thermal leptogenesis with emphasis on the theoretical uncertainties and discuss some implications for lepton and quark mass hierarchies, CP violation and dark matter. We also comment on the `leptogenesis conspiracy', the remarkable fact that neutrino masses may lie in the range where leptogenesis works best.Comment: 23 pages, 5 figures, submitted to the Focus on Neutrino Physics issue of the New Journal of Physics, edited by F. Halzen, M. Lindner and A. Suzuk

Cosmic Microwave Background, Matter-Antimatter Asymmetry and Neutrino Masses

We study the implications of thermal leptogenesis for neutrino parameters. Assuming that decays of N_1, the lightest of the heavy Majorana neutrinos, initiate baryogenesis, we show that the final baryon asymmetry is determined by only four parameters: the CP asymmetry epsilon_1, the heavy neutrino mass M_1, the effective light neutrino mass \tilde{m}_1, and the quadratic mean \bar{m} of the light neutrino masses. Imposing the CMB measurement of the baryon asymmetry as constraint on the neutrino parameters, we show, in a model independent way, that quasi-degenerate neutrinos are incompatible with thermal leptogenesis. For maximal CP asymmetry epsilon_1, and neutrino masses in the range from (\Delta m^2_{sol})^{1/2} to (\Delta m^2_{atm})^{1/2}, the baryogenesis temperature is T_B = O(10^{10}) GeV.Comment: 28 pages, 14 figures included; v2: erratum added, M_1 lower bound in the strong wash-out regime (see Eq. (63)) relaxed by a factor 2/

Analysis of cyclic delay diversity on DVB-H systems over spatially correlated channel

The objective of this work is to research and analyze the performance of Cyclic Delay Diversity (CDD) with two transmit antenna on DVB-H systems operating in spatially correlated channel. It is shown in this paper that CDD can achieve desirable transmit diversity gain over uncorrelated channel with or without receiver diversity. However, in reality, the respective signal paths between spatially separated antennas and the mobile receiver is likely to be correlated because of insufficient antenna separation at the transmitter and the lack of scattering effect of the channel. Under this spatially correlated channel, it is apparent that CDD cannot achieve the same diversity gain as obtained under the uncorrelated channel. In this paper, a new upper bound on the pairwise error probability (PEP) of the CDD with spatial correlation of two transmit antennas is derived. The upper bound is used to study the CDD theoretical error performance and diversity gain losses over a generalized spatially correlated Rayleigh channel. This theoretical analysis is validated by the simulation of DVB-H systems with two transmit antennas and the CDD scheme. Both the theoretical and simulated results give the valuable insight that the CDD ability to perform well with a certain amount of channel correlation

Evaluation of diversity gains for DVB-T systems

Copyright @ 2008 Eurescom GmbHThe requirements for future DVB-T/H networks demand that broadcasters design and deploy networks that provide ubiquitous reception in challenging indoors and other obstructed situations. It is essential that such networks are designed costeffectively and with minimized environmental impact. The EC funded project PLUTO has since its start in 2006 explored the use of diversity to improve coverage in these difficult situations. The purpose of this paper is to investigate the performance of transmit and receive diversity gains with two antennas to improve the reception of DVB-T/H systems operating in different realistic propagation conditions through a series of tests using the Spirent dual channel emulator

Extrajudicial Killings in Bangladesh: Exploring the Phenomenon of Human Rights Violations As a Means of Maintaing Power

When the South Asian nation of Bangladesh emerged as an independent nation on December 16, 1971, the founding fathers sought to establish a liberal democracy that would uphold the rule of law and the fundamental human rights of individuals. To this end, they incorporated extensive guarantees, including safeguarding the enforcement of an impressive eighteen fundamental rights, in the Constitution of Bangladesh of 1972. However, this Article will demonstrate that after almost fifty years of independence, the promise of a liberal democracy has remained elusive in Bangladesh due to the frequent violation of human rights through extrajudicial killings as a convenient means of maintaining power. Although successive governments have resorted to extrajudicial killings, the current government of the Bangladesh Awami League, which has ruled the nation uninterruptedly for the past twelve and a half years, has gone further than all previous governments in resorting to such killings to suppress any threat to its aspiration of perpetuating power. The regime’s contempt for the human rights of individuals is further evident from the fact that even during the COVID-19 pandemic, it has not shied away from resorting to extrajudicial killings to put down its adversaries. This Article will put forward recommendations for ensuring the realization of the elusive promise of a liberal democracy on which the nation was founded

The natural death of the Supreme Judicial Commission of Bangladesh and the consequent patronage appointments to the Bench: Advocating the establishment of an Independent Judicial Commission

In order to strengthen the constitutional process of appointment of judges in Superior Courts, Bangladesh established a Supreme Judicial Commission in 2008 by promulgating an Ordinance. This Ordinance was neither promulgated in pursuance of any provisions of the Constitution nor by introducing any amendment to the provisions of the Constitution. The recommendations of the Commission were not given binding force on the executive. The power of the executive to accept or reject the candidates recommended by the Supreme Judicial Commission at his pleasure defeated the very objective of establishing the Commission for appointing the most competent and suitable persons as judges of the superior courts in Bangladesh. However, following the general elections held on 29 December 2008, the newly elected Government of Bangladesh Awami League dispensed with the Supreme Judicial Commission by not placing the Supreme Judicial Commission Ordinance before the parliament for its approval. This resulted in restoring the previous system of appointing judges on the satisfaction of the executive, which has resulted in patronage appointments. Thus, the establishment of an independent judicial commission in Bangladesh is an imperative necessity for strengthening the independence and impartiality of the judiciary