Wednesday, October 26, 2011

Faster than light? Maybe not

While theorists have been sceptical about the faster than light neutrinos for a while, there is now a new experiment which casts further doubt on the results of the OPERA collaboration. The ICARUS experiment offers a rebuttal of the earlier claims of neutrinos travelling faster than light.

The ICARUS(Imaging Cosmic and Rare Underground Signals) experiment also collects neutrinos that travel from CERN to Gran Sasso, but measures the energy spectrum rather than the time of flight, as is done by the OPERA experiment, which is also located at Gran Sasso and reported superluminal (faster than light) speeds. ICARUS has shown that the energy spectrum does not show the signature of the Cohen-Glashow effect which is the analogue of the Cerenkov radiation emitted by charged particles. Charged particles such as electrons that travel in media with velocities greater than the velocity of light in that medium, emit radiation known as Cerenkov radiation, and lose energy in the process. If the neutrinos of the Opera experiment did travel with velocities greater than light, they would emit particles (electron, positron pairs and photons, mediated by a Z0 boson, as per Cohen and Glashow), and lose energy themselves in the process. There is a straightforward relation between the rate at which the neutrinos lose energy and the speed at which they travel. The average energy of the neutrinos that leave CERN is 28.2 GeV. If they actually travelled at superluminal speeds, they would reach Gran Sasso, where both OPERA, and ICARUS are located, with an average energy of 12.1 GeV. Instead, ICARUS reports that the neutrinos detected by them, have an average energy of 26 GeV, about what the neutrinos would have, if they travelled at the boring old speed of light!

By the way, ICARUS only has about 100 reliable neutrino events, whereas OPERA has about 16,000. However, the results of the ICARUS experiment rely on a straightforward measurement of the distribution of energies, and hence do not get mired down by issues like the synchronisation and slowing down of clocks that the time of flight experiments of OPERA do, and are being taken very seriously. As in all the other issues like the Tevatron bump, and the missing Higgs, which have come up recently, only more measurements, and further experiments by independent collaborations, can resolve the question. We look forward to more exciting results.

Tailpiece: Does E still equal mc squared? (The Corrigan brothers). We don't know yet, but that's the way to bet.

Happy Diwali, everyone.

This blog post is by Neelima Gupte and Sumathi Rao.

Tuesday, October 11, 2011

Three ladies (reprise)

So here are three ladies in the news again, and no prizes for guessing which three ladies they are: Ellen Johnson Sirleaf, Leymah Gbowee and Tawakkul Karmen, two Liberians and a Yemeni, in that order, and joint winners of the Nobel prize for peace this year. Tawakkul Karmen is the first Arab woman to win this prize, and her prize is the Nobel committee's recognition of the Arab spring, as well as of the role of the Islamists and of women in the uprisings. The first, i.e. the recognition of the Arab spring, could have been foreseen, but given the number of people who have contributed to it, and could have been considered contenders for the prize, the choice of the actual winner is truly progressive, and not quite on expected lines. The other two winners, President Sirleaf of Liberia, and Gbowe who organised the Women for Peace movement, an organisation of Muslim and Christian women against the Liberian warlords, are perceived widely as reformers and peacemakers.

The citation of the committee is both explicit and heartening, "We cannot achieve democracy and lasting peace in the world unless women obtain the same opportunities as men to influence developments at all levels of society." Since this message of female empowerment will be heard round the world, it will have its desired impact, and perhaps one day reality may rise to the ideal in the song:

"As we come marching, marching, we bring the greater days,
The rising of the women means the rising of the race,
No more the drudge and idler---ten that toil while one reposes,
But a sharing of life's glories: Bread and roses! Bread and roses!"

This post is by Neelima Gupte and Sumathi Rao

Sunday, October 2, 2011

The rise and fall of the Indian liberal tradition: A talk by Ramachandra Guha

An Indian liberal visited Chennai a few weeks ago, and gave a talk on his perception of the state of the liberal tradition in India. In addition to being a liberal, he is a well known historian, a polemical writer in the grand tradition of George Orwell, a cricket enthusiast, and last, but not least, a Stephenian. Those who caught all the cues, (and read the title of this post), would have zeroed in on Ramachandra Guha.

It is not so easy to identify who qualifies as an Indian liberal, so Guha started off with the dictionary definition of a liberal, i.e. favourable to or respectful of individual rights and freedoms, favouring individual liberty, free trade, and moderate political and social reform, regarding many traditional beliefs as dispensable, invalidated by modern thought, or liable to change. Out of these the OED distills an overall definition, viz. willing to respect or accept behaviour or opinions different from one’s own; open to new ideas. To these, the Indian liberal added some additional qualities, viz. hopefulness about the future, and implicit patriotism as exemplified by Tagore's notion of nationalism. The nationalist movement in the 1900-s threw up liberals like Raja Ram Mohan Roy, and Gopal Krishna Gokhale,who tried to liberalise the backward and ossified indigeneous tradition using ideas brought in by the technologically advanced colonisers. It was pointed out that all of these violated the dictionary definition, as they did not believe in free markets, and liberals such as Mahatma Gandhi and C. Rajagopalachari accepted many aspects of traditional and religious belief. Despite this, the constitutional privileges, secular structure and multilingual polity that Indians take for granted arise directly from this liberal tradition. The second phase of liberalism was from 1940-1950 where the liberal tradition upheld by Nehru and B.R. Ambedkar led to the Hindu Code Bill, equal rights for women, anti-caste legislation and support for the disadvantaged segments of society.

The liberal tradition faced its moments of crisis. The first arose in the period 1947-1950 when Mahatma Gandhi was shot dead and the liberal tradition faced attacks both from the resurgence of right wing religious fundamentalism, and from the Marxist fundamentalism and support for armed insurgency by a leftist party like the CPM. However, the center held, despite these threats, thanks to the strenuous efforts of Nehru, Patel and Ambedkar. The second attack on the liberal tradition came during 1971-1977 due to Indira Gandhi's authoritarianism and attempts to make the Indian National Conference a family firm. This destroyed the decentralised democratic structure of the Congress and created a cadre of committed civil servants and judiciary.

Today's threat to the liberal tradition comes from illiberal tendencies that arise from all directions, the left, the right and the center. The left contributes Maoist extremism, fueled by political economy, tribes displaced by development, and isolated by geographical terrain. The parties of the center contribute to corruption and family feudalism. Right wing fundamentalist ideas have not lost their attraction for certain segments of the polity.

So what can liberals do, to fight off this attack? Guha's prescription for the liberals is to stand firm against all forms of illiberalism. These include Hindu theocrats who feed paranoia, sycophants of political families, political opportunists, apologists for the Maoists, emotional blackmailers, and supporters of vigilante armies. He deplored the pussillanimity of the liberals, and said liberals should not be timid. He quoted Orwell who said a writer can never be a loyal member of a political party. He said that institution building is hard work, to which no substitutes or short cuts are available. The internet can spread ideas far and wide, but can also contribute to incivility. The media can spotlight a problem, but it can only be solved by debate, dialogue and receptivity. Finally, steady, patient work, away from the glare of the media, alone can provide lasting solutions to the evils that plague society.

This lecture was delivered at the Institute of Mathematical Sciences, Chennai, on September 7, 2011, as a memorial lecture for Rahul Basu.

This blog post is by Neelima Gupte and Sumathi Rao.