Conference and journal papers in physics I am preparing an interdisciplinary paper for publication in a leading physics journal. A preliminary version of this paper has been submitted to a conference in my field. Can the editors reject my paper based on this fact? In my field it would not be an issue. It is usually required that the journal paper expands on the contributions of the conference paper. In practice there a number of ways to overcome that requirement, so that it does not really matter. You need to submit a full paper to talk in a conference, so people use them as a first step of dissemination. But I do not know what is the relation between journal and conference papers in physics.
I have seen, at various times, deliveries at conferences that discuss papers which:


have been published, 
papers that have been submitted and accepted for publication, 
papers that have been submitted and are in the review process, and 
papers which are still being prepared for submission (including papers which have not yet been written).


Sometimes a conference paper is also prepared and published as conference proceedings, as a summary, lead-in or discussion of preliminary results which are then published in detail in a journal.

It is expected that the paper submitted to the journal will be different enough to the conference paper to be suitable for publishing as a separate article without infringing on the "not submitted elsewhere" condition, and you will probably also need to either cite the conference paper or the journal paper in the other to avoid plagiarism.