Hrvatski|English

Institute for Cosmology and Philosophy of Nature

Institut za kozmologiju i filozofiju prirode

Physics of the Universe

The scientific examination of the Universe does not simply mean the examination of physical systems outside Earth, but precisely the examination of the Cosmos as everything that is, including the interconnections between everything that exists. Accordingly, physics of the Universe represents the most general and fascinating front of theoretical physics, as well as the final test of the limits of our knowledge and our theories: from the largest scales ruled by gravity, through the middle scales of astrophysics to quantum scales and their interconnection with macroscopic scales within cosmological research of the past of the Universe. It is the physics of the Universe that raises the most difficult and deepest theoretical questions today (the unification of gravity and quantum theory, the nature of dark matter and dark energy), compelling us to develop new theories and enabling us to constantly test existing theories, still concealing from us a multitude of undiscovered phenomena. The Institute of Cosmology and Philosophy of Nature conducts space physics research by working in three related areas:

Physical Cosmology

Physical cosmology seeks to describe the Universe as a whole and to understand its evolution and origin, using the mathematical description of natural phenomena and concepts from theoretical physics. The standard cosmological model based on the general theory of relativity not only leads to the necessary crumbling of physics equations at some point in the past of the Universe (the so-called Big Bang singularity), but also opens a number of currently unresolved questions and problems: such as the nature of dark energy, the nature of dark matter, the horizon problem, and a new problem of inconsistency in the values of the Hubble parameter. Attempts are often made to solve these problems by adding new elements and parameters to the theory, often in the absence of any theoretical motivation – largely reminiscent of the artificial addition of new epicycles in the geocentric system to sustain it.

The project orientation of the Institute of Cosmology and Philosophy of Nature is based on the need to work on creating a new paradigm as an alternative to the standard cosmological model, guided by the need for a synthesis of quantum physics and general theory of relativity. Of particular interest in this regard is the work on building a theory of the cyclical Universe as an alternative to the paradigm of the Big Bang as the beginning of the Universe, and making attempts to resolve all open fundamental questions of cosmology within the framework of this alternative. Because the cyclical Universe requires the existence of effects that transcend the framework of classical general theory of relativity, this research is closely related to research in the field of gravity physics aimed at developing a quantum theory of gravity.

The high energy scales of earlier periods of development of the Universe are particularly interesting for studying the relationship between gravity and electromagnetism and potential quantum effects that could lead to their modification and manifestation of their hidden interconnections, which is also one of the Institute's research areas.

The Physics of Gravity

The unique status of gravity as a phenomenon arises firstly from its infinite reach and the fact that it is a universal interaction between all forms of matter, for the existence of which the only necessary element is mass. The importance of gravity is further emphasized in the general theory of relativity where the physics of gravity actually becomes the physics of space and time itself – what forms the basis of the description of reality in all other forms of interactions and theories. However, radical new insights into the structure of space-time of the general theory of relativity have not yet been successfully united with the principles of the second largest theory of physics – quantum mechanics. In addition, it is not yet known which path leads to the unification of these two theories. Despite all the experimental success of the general theory of relativity so far, we know that it cannot be a complete theory since its description is classical-deterministic rather than quantum-mechanical. Moreover, in order for the general theory of relativity to correctly describe the Universe we observe, it is necessary to – without any motivation – introduce the still unexplained parameters of dark matter and dark energy. Everything seems to point to all of these issues being interconnected. In addition to this, there is another – often ignored – aspect of this problem: quantum physics remains on the terrain of the old understanding of non-dynamic space and time and interactions as forces, surpassed by the general theory of relativity. Therefore, the question justifiably arises: can it be possible for quantum field theories to develop and incorporate the understanding of space-time of the general theory of relativity; or, in other words, can they approach a geometrical description?

Without pretentions to be able to solve this difficult problem in one step, the Institute of Cosmology and Philosophy of Nature pays special attention to the issue of effective work on approaching the theory of quantum gravity while solving the problem of dark energy and dark matter. Of particular importance are discussions on possible observational consequences and new phenomena that could manifest in regimes approaching the quantum gravity description. As one of the first steps in this direction, modified theories of gravity – as forms of mathematical generalizations of the general theory of relativity – and the study of their consequences are an important area of research.

High-energy Astrophysics

Astrophysics is primarily a scientific discipline the goal of which is to understand the nature of cosmic phenomena and objects using the concepts and knowledge of “earthly” physics. Secondly, astrophysics represents an immense and rich source of material and insight into, from the viewpoint of "terrestrial" physics, extreme systems, which is necessary for the advancement of fundamental knowledge, establishing the need for a universal understanding of what is close at hand – the "terrestrial", and what is inaccessible, or difficult to access – the "celestial”. Thus, astrophysics is a favorite playground of theoretical physics, where it not only regularly finds inspiration, but also tests its hypotheses.

Focusing on phenomena and objects that emit high-energy radiation and/or high-energy matter, high-energy astrophysics has developed as a separate sub-discipline of astrophysics. It is precisely high-energy astrophysics that studies systems of great importance for the further progress of theoretical physics and the realization of its aspiration for a deeper insight into the structure of matter, but also the unification of areas of general theory of relativity and quantum mechanics that are still separate. Turbulent stellar processes, compact objects of extreme masses, supernovae and their remnants, interstellar space filled with radiation, magnetic fields, known and perhaps unknown matter... these are all objects of study of high-energy astrophysics that require approaches and concepts that are unknown to terrestrial laboratories.

Research papers

  • Simulating the Galactic Multi-messenger Emissions with HERMES. Andrej Dundovic, Carmelo Evoli, Daniele Gaggero, Dario Grasso. e-Print: 2105.13165 [astro-ph.HE]. A&A 653, A18 (2021)
  • Dynamic properties of cyclic cosmologies. Petar Pavlović, Marko Sossich. e-Print: 2009.03625 [gr-qc]. Phys.Rev.D 103 (2021) 2, 023529
  • Novel aspects of cosmic ray diffusion in synthetic magnetic turbulence. Andrej Dundovic, Oreste Pezzi, Pasquale Blasi, Carmelo Evoli, William H. Matthaeus. e-Print: 2007.09142 [astro-ph.HE]. Phys.Rev.D 102 (2020) 10, 103016
  • Influence of the Vacuum Polarization Effect on the Motion of Charged Particles in the Magnetic Field around a Schwarzschild Black Hole. Petar Pavlović, Andrey Saveliev, Marko Sossich. e-Print: 1908.01888 [gr-qc]. Phys.Rev.D 100 (2019) 8, 084033
  • Anisotropies of Ultra-high Energy Cosmic Rays Dominated by a Single Source in the Presence of Deflections. Andrej Dundović, Günter Sigl. e-Print: 1710.05517 [astro-ph.HE]. JCAP 01 (2019), 018
  • Effect of vacuum polarization on the magnetic fields around a Schwarzschild black hole. Petar Pavlović, Marko Sossich. e-Print: 1809.06054 [gr-qc]. Phys.Rev.D 99 (2019) 2, 024011
  • On minimal energy states of chiral MHD turbulence. Petar Pavlović, Günter Sigl. e-Print: 1806.06447 [hep-th]. JCAP 04 (2019), 055
  • Magnetogenesis in Cyclical Universe. Natacha Leite, Petar Pavlović. e-Print: 1805.06036 [gr-qc]. Class.Quant.Grav. 35 (2018) 21, 215005
  • The Effects of Running Gravitational Coupling On Rotating Black Holes. Sumarna Haroon, Mubasher Jamil, Kai Lin, Petar Pavlovic, Marko Sossich et al. e-Print: 1712.08762 [gr-qc]. Eur.Phys.J.C 78 (2018), 519
  • Cyclic cosmology in modified gravity. Petar Pavlovic, Marko Sossich. e-Print: 1701.03657 [gr-qc]. Phys.Rev.D 95 (2017) 10, 103519
  • Chiral Magnetohydrodynamic Turbulence. Petar Pavlović, Natacha Leite, Günter Sigl. e-Print: 1612.07382 [astro-ph.CO]. Phys.Rev.D 96 (2017) 2, 023504
  • Propagation of ultrahigh energy cosmic rays in extragalactic magnetic fields: a view from cosmological simulations. Stefan Hackstein, Franco Vazza, Marcus Brüggen, Guenter Sigl, Andrej Dundovic. e-Print: 1607.08872 [astro-ph.CO]. Mon.Not.Roy.Astron.Soc. 462 (2016) 4, 3660-3671
  • Cosmological wormholes in f(R) theories of gravity. Sebastian Bahamonde, Mubasher Jamil, Petar Pavlovic, Marko Sossich. e-Print: 1606.05295 [gr-qc]. Phys.Rev.D 94 (2016) 4, 044041
  • CRPropa 3 - a Public Astrophysical Simulation Framework for Propagating Extraterrestrial Ultra-High Energy Particles. Rafael Alves Batista, Andrej Dundovic, Martin Erdmann, Karl-Heinz Kampert, Daniel Kuempel, et al. e-Print: 1603.07142 [astro-ph.IM]. JCAP 05 (2016), 038
  • Modified Magnetohydrodynamics Around the Electroweak Transition. Petar Pavlović, Natacha Leite, Günter Sigl. e-Print: 1602.08419 [astro-ph.CO]. JCAP 06 (2016), 044
  • Wormholes in viable f(R) modified theories of gravity and Weak Energy Condition. Petar Pavlovic, Marko Sossich. e-Print: 1406.2509 [gr-qc]. Eur.Phys.J.C 75 (2015), 117