Lifeboat Foundation

The purpose of this work is to investigate how several inflationary and bouncing scenarios can be realized by imperfect fluids. We shall use two different theoretical frameworks, namely classical cosmology and Loop Quantum Cosmology (LQC) (see where the derivation of the Hamiltonian in LQC was firstly derived to yield the modified Friedman equation, and also see for a recent derivation of the effective Hamiltonian in LQC, which was derived by demanding repulsive gravity, as in Loop Quantum Gravity). In both cases we shall investigate which imperfect fluid can realize various inflationary and bouncing cosmology scenarios. The inflationary cosmology and bouncing cosmology are two alternative scenarios for our Universe evolution. In the case of inflation, the Universe starts from an initial singularity and accelerates at early times, while in the case of the bouncing cosmology, the Universe initially contracts until it reaches a minimum radius, and then it expands again. With regards to inflation, we shall be interested in four different inflationary scenarios, namely the intermediate inflation, the Starobinsky inflation, and two constant-roll inflation scenarios. With regards to bouncing cosmologies, we shall be interested in realizing several well studied bouncing cosmologies, and particularly the matter bounce scenario, the superbounce scenario and the singular bounce.

As we already mentioned we shall use two theoretical frameworks, that of classical cosmology and that of LQC. After presenting the reconstruction methods for realizing the various cosmologies with imperfect fluids, we proceed to the realization of the cosmologies by using the reconstruction methods. In the case of classical cosmology, we will calculate the power spectrum of primordial curvature perturbations, the scalar-to-tensor ratio and the running of the spectral index for all the aforementioned cosmologies, and we compare the results to the recent Planck data. The main outcome of our work is that, although the cosmological scenarios we study in this paper are viable in other modified gravity frameworks, these are not necessarily viable in all the alternative modified gravity descriptions. As we will demonstrate, in some cases the resulting imperfect fluid cosmologies are not compatible at all with the observational data, and in some other cases, there is partial compatibility.

We need to note that the perturbation aspects in LQC are not transparent enough and assume that there are no non-trivial quantum gravitational modifications arising due to presence of inhomogeneities. As it was shown in, a consistent Hamiltonian framework does not allow this assumption to be true. The perturbations issues that may arise in the context of the present work, are possibly more related to some early works in LQC, so any calculation of the primordial power spectrum should be addressed as we commented above.

Roughly 4 billion years ago, Earth was developing conditions suitable for life. Origin-of-life scientists often wonder if the type of chemistry found on the early Earth was similar to what life requires today. They know that spherical collections of fats, called protocells, were the precursor to cells during this emergence of life. But how did simple protocells first arise and diversify to eventually lead to life on Earth?

Now, Scripps Research scientists have discovered one plausible pathway for how protocells may have first formed and chemically progressed to allow for a diversity of functions.

The findings, published online on February 29, 2024, in the journal Chem, suggest that a chemical process called phosphorylation (where phosphate groups are added to the molecule) may have occurred earlier than previously expected. This would lead to more structurally complex, double chained protocells capable of harboring chemical reactions and dividing with a diverse range of functionalities. By revealing how protocells formed, scientists can better understand how early evolution could have taken place.

Alex Rosenberg is the R. Taylor Cole Professor of Philosophy at Duke University. His research focuses on the philosophy of biology and science more generally, mind, and economics.

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In a new study, scientists have mapped magnetic fields in galaxy clusters, revealing the impact of galactic mergers on magnetic-field structures and challenging previous assumptions about the efficiency of turbulent dynamo processes in the amplification of these fields.

Galaxy clusters are large, gravitationally bound systems containing numerous galaxies, hot gas, and dark matter. They represent some of the most massive structures in the universe. These clusters can consist of hundreds to thousands of galaxies, bound together by gravity, and are embedded in vast halos of hot gas called the intracluster medium (ICM).

ICM, consisting mainly of ionized hydrogen and helium, is held together by the gravitational pull of the cluster itself. Magnetic fields in large-scale structures, like galaxy clusters, play pivotal roles in shaping astrophysical processes. They influence the ICM, impact galaxy formation and evolution, contribute to cosmic ray transport, participate in cosmic magnetization, and serve as tracers of large-scale structure evolution.

Researchers at the University of Massachusetts Amherst recently released a first-of-its-kind study focusing on the rare autoimmune disorder aplastic anemia to understand how a subset of cells might be trained to correct the overzealous immune response that can lead to fatal autoimmune disorders. The research, published in Frontiers in Immunology, identifies a specific enzyme known as PRMT5, as a key regulator of suppressive activity in a specialized population of cells.

The human immune system is a marvel of evolution. When a pathogen enters the body, immune cells can identify it, call for backup, attack the pathogen, and then, when the threat has been eradicated, return to a peaceful state. But sometimes, as in the rare autoimmune disorder aplastic anemia, something goes wrong.

In patients with aplastic anemia, the aberrant immune cells, in this case Th1 cells, misidentify healthy stem cells in bone marrow as pathogenic and attack them. Without these bone marrow stem cells, the body can’t make white blood cells to fight infections, red blood cells to carry oxygen throughout the body, or platelets that help stop bleeding.

We now have a standard model of cosmology, the current version of the Big Bang theory. Although it has proved very successful, its consequences are staggering. We know only 5% of the content of the universe, which is normal matter. The remaining 95% is made up of two exotic entities that have never been produced in the laboratory and whose physical nature is still unknown.

These are dark matter, which accounts for 25% of the content of the cosmos, and dark energy, which contributes 70%. In the standard model of cosmology, dark energy is the energy of empty space, and its density remains constant throughout the evolution of the universe.

According to this theory, sound waves propagated in the very early universe. In those early stages, the universe had an enormous temperature and density. The pressure in this initial gas tried to push the particles that formed it apart, while gravity tried to pull them together, and the competition between the two forces created sound waves that propagated from the beginning of the universe until about 400,000 years after the Big Bang.

Researchers report in the journal Cell that ancient viruses may be to thank for myelin—and, by extension, our large, complex brains.

The team found that a retrovirus-derived genetic element or “retrotransposon” is essential for myelin production in mammals, amphibians, and fish. The gene sequence, which they dubbed “RetroMyelin,” is likely a result of ancient viral infection, and comparisons of RetroMyelin in mammals, amphibians, and fish suggest that retroviral infection and genome-invasion events occurred separately in each of these groups.

“Retroviruses were required for vertebrate evolution to take off,” says senior author and neuroscientist Robin Franklin of Altos Labs-Cambridge Institute of Science. “If we didn’t have retroviruses sticking their sequences into the vertebrate genome, then myelination wouldn’t have happened, and without myelination, the whole diversity of vertebrates as we know it would never have happened.”

Polyploidization-rediploidization process plays an important role in plant adaptive evolution. Here, the authors assemble the genomes of mangrove species Sonneratia alba and its inland relative Lagerstroemia speciosa, and reveal genomic evidence for rediploidization and adaptive evolution after the whole-genome triplication.

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Heme proteins can catalyze the formation of carbon–silicon bonds.