The branch of physics that deals with the concept of dimensions, particularly in relation to theories like string theory and higher-dimensional spacetime, is called theoretical physics or theoretical particle physics. More specifically, it falls under the domain of theoretical physics that focuses on fundamental theories and attempts to understand the fundamental nature of the universe.
The study of dimensions in theoretical physics involves exploring the possibility of additional spatial dimensions beyond the three dimensions (length, width, and height) that we experience in our everyday lives. These extra dimensions are often posited in various theoretical frameworks, including string theory and some other theories of quantum gravity.
Theoretical physicists use advanced mathematical tools and concepts from fields such as quantum mechanics, general relativity, and differential geometry to develop and analyze these theories. They explore the implications of higher-dimensional spacetime and investigate how these additional dimensions might be hidden or compactified at scales much smaller than we can currently detect.
It's important to note that the concept of dimensions in theoretical physics goes beyond the popularized portrayals you may see on TV or the internet. While these portrayals can generate interest and curiosity, they often oversimplify or exaggerate the scientific ideas. If you are interested in exploring the concept of dimensions in physics, it is recommended to study the subject through reputable scientific sources, books, or academic courses that delve into the mathematical and theoretical aspects of the field.