Who are the shining stars among PhD students? Alison Goddard asked six supervisors to nominate those pursuing the most innovative ideas

Doing a PhD is like giving birth - it is painful, drawn out and a joy when it is over." So speaks one researcher who submitted her thesis earlier this year. But despite the difficulties - low social status and negligible pay - more than 5,000 bright brains will embark on a doctorate in October.

Driven by a romantic excitement, they are enthusiastic about adding to the body of human knowledge. So what are the ideas propelling their intellectual toil - what are Britain's young research stars investigating? And will their final discoveries be worth the labour?

Three of the six, including one Briton, have been offered jobs in the United States. All but one want to become fully fledged academics.

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A flock of sculptors

"A white marmorean flock" is how the author Henry James described the American women sculptors he met in 19th-century Rome. Nancy Proctor, in the third year of her PhD at the University of Leeds, is exploring the position of these women in the history of art.

The role of the sculptors has been neglected, says Proctor's supervisor, Griselda Pollock, who believes the women were excluded from art history because no one expected them to be there. "Nancy's is a very creative thesis on the theme of estrangement," she says.

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"I was very surprised to discover that there were American women sculptors in Rome (between 1848 and the 1880s)," concedes Proctor, who spent a semester in Rome while studying for her degree in classics and art history at an American university.

Building on previous work, she has identified 14 professional sculptors - including Harriet Hosmer, Anne Whitney, Edmonia Lewis and Emma Stebbines. They worked in white marble or bronze, creating idealised neo-classical pieces based on classical and biblical themes and legends. Whitney was also known for pieces that expressed her social concerns, embodying antislavery sentiments and the movement for women's rights. And Lewis was noted for drawing on themes of native Africans and African Americans.

"People say that there is no point in talking about their work because it is so crap," says Proctor, who prefers not to make value judgements. "They worked in a romantic style that has not been in favour since the 1880s, but in their day they were thought to be excellent."

Far from living as a feminist cooperative, the women came to Rome for very different reasons, according to Proctor. She has made extensive library searches for references to the women, and toured Rome and the United States in search of surviving pieces of their work. "There were professional rivalries between the women," she says. "At some points, they quit speaking to each other, perhaps when one got a commission the others wanted."

And she is convinced of the importance of the women's role in the history of art. "I believe that if we are going to understand American art and American modernism in particular," she says, "then we really need to understand these women."

Mexican migrants

Anthropologist Victoria Malkin spent 18 months painstakingly tracking the illegal movement of women between two Mexican towns and a New York suburb.

She lived in all three communities in a bid to trace the migrant networks, including a spell living with a doctor's family in a poor town of 5,000 people in western Mexico. Surviving on a shoestring - her project was turned down for funding by the research councils - she came up with the women's names herself rather than relying on the records of official bodies. This allowed her to identify some women who had migrated illegally.

She will not publish the names of the towns in her thesis, since protocol in social anthropology dictates that no individual should be identifiable from the research. But she says that they "had a tradition of migration since the start of the century" and "nearly everyone had a relative in the US".

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To gather information, she conducted household surveys and joined church groups where she could socialise with local women.

Malkin was particularly interested in how a person's gender affects their view of migration. Immigrants now maintain strong ties with their mother country, she says, and Mexicans no longer become American on entering the US. Instead, Mexicans construct an identity around themselves while abroad. But there is a difference between the role of women in New York and in Mexico. "A community has its own ideas on what being Mexican means," says Malkin. In Mexico these include being a good wife and mother.

"The classical western feminist viewpoint does not capture the hopes and aspirations of these women," says John Gledhill, Malkin's supervisor at the University of Manchester, who heaps praise on his student: "Transnational processes are a buzz issue in social anthropology. This is a truly innovative piece of work."

And it has lessons for Britain too. "Migrants can come to a country and generate their own identity. It is important to realise this, as the same processes are at play here," says Malkin.

Bronze Age child labour

"Did Bronze Age children work in the copper mines of the Great Orme in North Wales? That is one question Emma Wager, a PhD student at the University of Sheffield, is trying to answer.

She is examining the social context of this prehistoric mine. Previous work has looked at the technical challenges of mining in the Bronze age, according to her supervisor, Barbara Ottaway, but Wager's job is to create a holistic picture. That means interpreting information to generate a story of the people who worked the mine.

The Great Orme is one of the biggest Bronze Age copper mines in Europe. Its shafts are up to 70 metres deep and still show the marks made by bone tools. Some galleries are so narrow that only a child could have mined them. This implies that whole societies were involved in mining and smelting the ore. But was there a permanent settlement at the Great Orme? And did it have a supporting agricultural structure?

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Wager is conducting fieldwork to address these questions, reading other studies and questioning cavers and walkers. She has completed a small-scale excavation herself, which revealed mainly mining spoil that had possibly been reworked in the 19th century.

The role of prestige goods is important, she says. Axes could be status symbols, denoting identity and power. As part of her masters degree, Wager smelted weaponry to test whether the Bronze Age weapons discovered on the Great Orme were used or whether they were ceremonial artefacts. By casting her own weapons, and clashing them with metal, wood and leather, she created notches typical of those found in Bronze Age items and concluded they were used for combat.

And Wager is also examining ethnographic evidence to try to determine the importance of smelting to primitive societies. There might be all sorts of rituals, she says. "I find it interesting to look at how people in the past may have lived," she says. "It informs my way of life."

Glittery black holes

As a schoolgirl, Tiziana Di Matteo was fascinated by physics and astrophysics. "I wanted to understand the evolution of the universe," she says. "It is a romantic idea." Now, for her PhD at the University of Cambridge, Di Matteo is studying why some of the discs of material that surround black holes glow more brightly than others. "There are huge black holes at the centre of many galaxies," she says. "But the black holes in nearby galaxies don't display the same exotic phenomena as those further away."

According to theory, young black holes accumulate a disc of glowing material around them. As this material is swallowed by the black hole, the remaining disc glows less brightly. "As time passes, the system starves and you can no longer see the effects of the black hole," explains Di Matteo. Therefore the discs surrounding nearby black holes should glow less brightly than those further away in space and time.

There are several theories why this could be so. Di Matteo is pursuing one of them, which was recently revived by her supervisor, Andy Fabian. To do this, she has written computer programs that simulate what the disc surrounding a black hole should look like according to the theory. Di Matteo then compares her predictions with observations taken by the Very Large Array in the US and the British James Clerk Maxwell Telescope on Hawaii.

But when she compared her computer models with telescopic observations she found that they did not tally. "Although the model looks extremely good, the data does not agree, by an order of magnitude," says Fabian. "It is an interesting project - this is the first clearly observed result that suggests there are problems with the theoretical model of how black holes should appear."

A unified economics thesis

A new trend is emerging in economics: the PhD thesis that is unified by applying similar tools to diverse problems rather than using different tools to tackle a single issue. Henry Overman, a third-year student at the London School of Economics, will submit this new style of thesis.

Danny Quah of the LSE's centre for economic performance is Overman's supervisor. He thinks the new style is much more logical. An old-style PhD is like a book, says Quah, whereas a themed approach is more like a series of journal articles. "The economics profession works by way of journal articles," he points out. And the best books are written by older, more experienced academics who have an extended vision that students lack.

Overman is developing tools to account for regional economic growth. For example, he is using a set of statistical tools to examine the effect of industrial investment. "The EU wants to find out whether spending from its cohesion fund in Portugal, Ireland, Spain and Greece has spilled over into other economies," he says. In particular, it wants to demonstrate whether there are benefits for countries like Germany.

But to do this, Overman needs to disentangle whether new industry is genuinely being created or whether it is merely relocating from elsewhere. "It is an incredibly topical issue and it is also academically controversial," he says. The research will feed into the "new economic geography" debate on where industry locates across Europe. "Policy-makers in Europe really care about the results and there is a resurgence in academic thought on these big issues."

The meaning of marriage

"Marriage, contract and the state" is the title of philosopher Elizabeth Brake's thesis. Her supervisor at the University of St Andrews, David Archard, describes her work as "very original".

The thesis addresses issues such as the meaning of marriage and the role of the state in promoting gender equality. "What does the moral value of marriage mean? People refer to it without really knowing. Is it the right to possess (another person) or is it a spiritual union?" she asks.

As part of her research, Brake has identified writings by 18th-and 19th-century philosophers such as Immanuel Kant and Georg Hegel. "Kant's moral theory contains a contractual account of marriage," she says. "But his account is outdated or worse. In fact, it contradicts his own moral system since it justifies treating a person as a thing." She also uses Hegel's concept of ethical life to explore the moral status of marriage. "I read enormous amounts of material and try to understand what the arguments are, to summarise them," she says.

This brings her neatly to the question of how the state should legislate marriage. One view is that the state should not interfere in the private lives of individuals, she says. But another says that to achieve equality between the sexes requires state intervention in the form of a contract.

"It is an important issue for feminist and political authors. And as well as being theoretical, it is a practical issue in jurisprudence and law," says Brake.

"Her work is at the intersection between feminism, feminist theory, jurisprudence and social philosophy," says Archard. "It is a matter of some controversy between feminist authors as to whether the marriage contract is at all welcome for women."

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Moreover, "in an era when family, marriage and relationships have undergone enormous change, it is important to have a contemporary interpretation of their significance," he adds.