Dear Colleagues,

The discovery of cosmic rays has opened a door through which we can glimpse the non-thermal Universe at the highest energies; in addition, it has led to the birth of astroparticle physics. Symmetry plays an important role in particle physics, since every conservation law, interaction, even the particle masses, can be derived from symmetries (or from their violation), and it is no different for astroparticle physics either. Though great steps have been taken to realize their nature, the cosmic ray enigma is still an open and actively studied question. We are soliciting contributions covering a broad range of topics on astroparticle physics from both observation and theory angles, including (though not limited to) the following:

- Symmetries in astroparticle physics;

- Possible physics and new symmetries beyond the standard model of particle physics;

- Origin (steady and transient sources), spectrum and mass composition of UHECRs;

- Galactic to extragalactic transition in the cosmic ray spectrum; UHECR sources beyond the ankle;

- Galactic and extragalactic sources of high-energy neutrinos and gamma photons;

- Multimessenger studies of potential astroparticle accelerators;

- Cosmological studies on the high-energy Universe.

Dr. Emma Kun
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• symmetries
• cosmic rays
• high-energy neutrinos
• gamma photons
• particle acceleration
• cosmology
• black holes