This thesis is centred on the analysis of how the different groups of specialist experts that make up theoretical physics at large communicate and transmit knowledge between themselves. The analysis is carried out using two sociological frameworks: the Studies in Expertise and Experience (SEE) approach Collins and Evans, and mechanisms of sociological and institutional trust in the general sociology of science literature. I argue that the communication process is carried out in two ways: through interactional expertise that is based on deep comprehension when the interaction is between micro-cultures that are sociologically closely connected, and through lower forms of knowledge relying on trust for the micro-cultures that are sociologically far apart. Because the SEE framework is strongly based on the transmission of tacit knowledge, an analysis of the importance of tacit knowledge in theoretical physics is carried out to support the SEE analysis, and specific types of tacit knowledge are closely examined to understand how they shape theoretical physics practice. I argue that `physical intuition', one of the guiding principles of all theoretical activity, is in fact a type of tacit knowledge -somatic tacit knowledge- that is well known within social studies of science. The end result is a description of physics that highlights the importance of sociological mechanisms that hold the discipline together, and that permit knowledge to flow from the empirical to the theoretical poles of physics practice. The thesis is supported by unstructured interview material and by the author's prolonged interaction within theoretical physics professional circles