BERLIN, April 3 (Xinhua) -- More than 2,000 mathematicians have signed a petition urging the International Mathematical Union (IMU) to move the 2026 International Congress of Mathematicians (ICM) out of the United States over safety concerns, visa restrictions for many countries, and U.S. geopolitical actions. Thus, what began as a dispute over the July meeting in Philadelphia evolved into a wider debate over whether the United States remained a secure and welcoming venue for global academic exchange.
GROWING COLLECTIVE REFUSAL
Since mid-March, the petition has spread rapidly through the mathematics community, with some of the world's most prominent mathematicians saying they would not take part if the congress went ahead in the United States.
The petition advanced two main arguments. The first concerned the risks of traveling to the United States. "The current American government has demonstrated in no uncertain terms its unbridled hatred of immigrants," the petition said. It argued that visa restrictions, border enforcement practices and detention cases had increased the uncertainty and danger facing international scholars seeking to enter the country.
The petitioners cited a recent Supreme Court ruling that allowed government agents to stop and question civilians about their immigration status based solely on "racial appearance or what language they speak." It also pointed to multiple cases in which U.S. citizens were detained, abused or killed after being caught up in enforcement actions.
"The IMU is inviting mathematicians from all over the world to come to the United States as people who may not look to an ICE agent as though they 'belong,'" the petition said, warning that they could therefore be subject to "indiscriminate harassment and physical violence."
The petition's second line of criticism concerned U.S. foreign policy. It argued that recent U.S. military and diplomatic actions were destabilizing the world, citing, among other examples, the "illegal kidnapping" of Venezuela's leader, continued extrajudicial killings in the Caribbean, a "brazen and thoughtless war on Iran," and what it described as an attempt to colonize Greenland.
These actions, the petition said, showed a "flagrant disregard of basic humanity all around the world."
"If the goal of the ICM is to encourage a sense of international unity among mathematicians, the IMU would completely fail on its own terms were it to go through with its plans to host the conference in the United States," it said.
TWO CONGRESSES, DOUBLE STANDARDS
The ICM is the premier global gathering for mathematics and one of the field's most symbolic events. Established in Zurich, Switzerland, in 1897 and held every four years, the congress serves as both a hub for academic exchange and the stage for the Fields Medal -- often hailed as the "Nobel Prize of Mathematics." The 2026 meeting will mark the event's first return to U.S. soil in four decades.
In a statement issued on March 30, the Berlin-based IMU acknowledged widespread anxieties regarding U.S. entry and the ability of scholars to feel "safe and welcome" in Philadelphia. Despite these concerns, the Union maintained its stance and confirmed it would not reconsider the venue.
"At a time when international collaboration and science face serious challenges, we strongly believe that holding the ICM in person in Philadelphia is especially important," the statement said.
Petitioners, however, saw this persistence as a glaring inconsistency. They pointed to the important precedent set in 2022, when the IMU moved the congress online to avoid holding it in Russia following the outbreak of the Russia-Ukraine conflict.
The petition argued that the safety risks in the United States were now equally, if not more, severe: "There is simply no sound argument one could make that claims international participants are safer at this iteration of the ICM than they would have been in Russia in 2022."
"Holding the ICM in the United States, after it started two illegal wars, represents a double standard," Michael Harris, a mathematician at Columbia University, said.
PHILADELPHIA PARADOX
The backlash had already gained institutional weight. As early as January, the French Mathematical Society (SMF) announced its withdrawal from all activities related to the 2026 congress in Philadelphia. It cited uncertainty over U.S. visa issuance, concerns about domestic security in the United States, and what it saw as an erosion of scientific values and academic freedom.
The statement also made special mention of Benjamin Franklin, one of Philadelphia's most enduring historical symbols. "The SMF remains fundamentally attached to the legacy of Benjamin Franklin, inseparable from rational thought, and condemns distrust of science and any infringement on academic freedoms," it said.
The Brazilian Mathematical Society also joined the protest. In a statement in February, it said recent U.S. measures had "hampered global scientific cooperation and violated the basic principles of freedom of movement and international collaboration," and announced that it would not organize official activities at this year's congress.
Anxiety over the U.S. academic environment was no longer confined to the world of mathematics. The International Studies Association (ISA) listed "Is it safe to travel to the U.S. for ISA 2026?" among its frequently asked questions and answers: "It depends." The association said there was greater uncertainty than in past years because of unpredictable policy changes and increased discretion by immigration officers.
Other scientific bodies issued similar warnings. The American Chemical Society advised international participants to verify travel bans and entry restrictions before traveling to the United States, while a conference hosted by Dartmouth College warned that the final decision on admission rested with border officials and that, in "very rare cases," travelers might even be asked to withdraw their application for admission.
"In today's America, internationalism is seen as threatening and isolationism seems to be the trajectory the U.S. is on," wrote Martina Kohl, a public diplomacy specialist and former U.S. Embassy official in Germany, warning that exchanges of ideas and serious research led by U.S. institutions would thus face growing obstacles. ■
