Washington

Despite increasing political tension, a group of US researchers are standing by their pledge to visit Iran this autumn for a workshop on superstrings.

Lack of money almost forced the team to abandon the trip. Getting the funds has been difficult, says trip organizer Albion Lawrence of Brandeis University in Waltham, Massachusetts. Fundraising was delayed for months by the war in Iraq and the current row over Iran's nuclear programme.

But on 25 June the problem was solved for seven members of the twelve-strong group. The Clay Mathematics Institute, a Boston-based charity, pledged $12,000 for the researchers to travel to Tehran. The National Science Foundation (NSF) has denied funds to graduate students who want to attend.

The meeting is organized by the Iranian Institute for Studies in Theoretical Physics and Mathematics in Tehran, which has held an annual school and workshop on string theory for the past three years.

This year's conference, near Anzali, on the Caspian Sea, from 29 September to 9 October, will be the first to have significant US participation. “This is an important development in scientific relations between US and Iranian scientists,” says Farhad Ardalan, a theorist at the Tehran institute and one of the meeting's organizers.

String theory postulates that particles can be described as vibrating loops or strings. “In the past few years, a strong group of string theorists has developed in Iran,” says Eva Silverstein, a theorist at the Stanford Linear Accelerator Center in California who will attend the meeting.