Is it permissible to break the fast in Ramadan due to a two-hour PhD exam discussion after Asr, knowing that there will be fatigue and lack of concentration after this time?

It is not permissible to break the fast in Ramadan (definition) due to an exam or lack of concentration. Fasting Ramadan is an obligation upon every accountable Muslim, and breaking the fast is only permissible for those with authorized excuses, such as the traveler, the sick, the pregnant, the breastfeeding, the elderly, and one who is coerced. The fatwas of the Permanent Committee for Scholarly Research and Ifta have stipulated that school exams and the like are not a permissible excuse for breaking the fast, and obedience to parents in this matter is not allowed because "there is no obedience to a creature in disobedience to the Creator."