The question of whether a unified field theory is possible without combining Einstein's general relativity with quantum mechanics is a topic of ongoing scientific research and debate. At present, there is no definitive answer to this question.
Einstein's general theory of relativity provides a description of gravity in terms of the curvature of spacetime. It has been tremendously successful in explaining the behavior of gravitational phenomena on large scales, such as the motion of planets and galaxies. On the other hand, quantum mechanics describes the behavior of matter and forces on very small scales, such as atoms and subatomic particles, and has been extremely successful in explaining the behavior of fundamental particles and their interactions.
However, these two theories, general relativity and quantum mechanics, have different mathematical frameworks and conceptual foundations that make their combination challenging. The mathematics of general relativity operates in a smooth and continuous spacetime, while quantum mechanics introduces discrete quantities and probabilistic behavior. Combining the two theories in a consistent and mathematically rigorous manner has proven to be a difficult task, resulting in what is known as the problem of quantum gravity.
Many physicists believe that a complete and fundamental description of the universe would require a theory that unifies general relativity and quantum mechanics. Such a theory is often referred to as a theory of quantum gravity or a unified field theory. Several approaches, such as string theory, loop quantum gravity, and others, have been proposed in an attempt to reconcile these two fundamental theories. However, at this point, none of these approaches has been definitively proven or widely accepted as the ultimate theory of quantum gravity.
In summary, the quest for a unified field theory that combines general relativity and quantum mechanics is an active area of research, and it remains an open question whether such a theory can be achieved without merging these two pillars of modern physics.