Cosmic Structure Formation in the Limit of Small Scales within Kinetic Field Theory

The amplitude and shape of the density fluctuation power spectrum today are determined by the initial conditions set after inflation, the properties of dark matter particles and the growth of structures due to the gravitational interaction in an expanding spacetime. Since cosmic structure formation is highly non-linear, the impact of the properties of dark matter on today’s structure or results from N-body simulations like the observed universal halo density profiles, are hard to understand with conventional analytical methods. While these approaches break down at small scales when particle streams cross, Kinetic Field Theory (KFT) operates with a generating functional in classical N-particle phase space, circumventing those problems. In this work, we present novel asymptotic methods that apply to rapidly oscillating integrals with two large parameters. Applying these methods to KFT, we derive the asymptotic limit of the power spectrum on small scales in the Zel’dovich approximation. The power spectrum universally develops a k^−3 tail, independent of the steepness of the initial spectrum, suggesting that scale-invariant structures form below a characteristic length scale already early in cosmic history. Finally, we derive the asymptotics of the factors of the factorized generating functional to guide their numerical implementation. These factors are indispensable for the numerical evaluation of perturbation theory and density correlation functions of high order within the framework of KFT

On the asymptotic behaviour of cosmic density-fluctuation power spectra

We study the small-scale asymptotic behaviour of the cosmic density-fluctuation power spectrum in the Zel'dovich approximation. For doing so, we extend Laplace's method in arbitrary dimensions and use it to prove that this power spectrum necessarily develops an asymptotic tail proportional to $k^{-3}$ , irrespective of the cosmological model and the power spectrum of the initial matter distribution. The exponent $-3$ is set only by the number of spatial dimensions. We derive the complete asymptotic series of the power spectrum and compare the leading- and next-to-leading-order terms to derive characteristic scales for the onset of non-linear structure formation, independent of the cosmological model and the type of dark matter. Combined with earlier results on the mean-field approximation for including particle interactions, this asymptotic behaviour is likely to remain valid beyond the Zel'dovich approximation. Due to their insensitivity to cosmological assumptions, our results are generally applicable to particle distributions with positions and momenta drawn from a Gaussian random field. We discuss an analytically solvable toy model to further illustrate the formation of the $k^{-3}$ asymptotic tail.Comment: 22 pages, 4 figues, to be submitted to SciPost Physics Added arguments to section 1 and section 5, results unchange

On the asymptotic behaviour of cosmic density-fluctuation power spectra of cold dark matter

We study the small-scale asymptotic behaviour of the cold dark matter density fluctuation power spectrum in the Zel'dovich approximation, without introducing an ultraviolet cut-off. Assuming an initially correlated Gaussian random field and spectral index $0 < n_s < 1$, we derive the small-scale asymptotic behaviour of the initial momentum-momentum correlations. This result is then used to derive the asymptotics of the power spectrum in the Zel'dovich approximation. Our main result is an asymptotic series, dominated by a $k^{-3}$ tail at large wave-numbers, containing higher-order terms that differ by integer powers of $k^{n_s-1}$ and logarithms of $k$. Furthermore, we show that dark matter power spectra with an ultraviolet cut-off develop an intermediate range of scales, where the power spectrum is accurately described by the asymptotics of dark matter without a cut-off. These results reveal information about the mathematical structure that underlies the perturbative terms in kinetic field theory and thus the non-linear power spectrum. We also discuss the sensitivity of the small-scale asymptotics to the spectral index $n_s$.Comment: 21 pages, 1 table, 6 figures; to be submitted to SciPost Physic

Cardiovascular comorbidities in acromegaly

Introduction and purpose: Acromegaly is a rare disease which occurs with the frequency of 0.2-1.1 cases per 100 000 patients per year. The main cause is the excess level of growth hormone (GH) which stimulates the liver to the insulin-like growth factor type 1 (IGF-1) secretion. IGF-1 leads to the tissues overgrowth. In addition, acromegalic patients suffer from many comorbidities, such as: cardiovascular, endocrinological, neoplastic and musculoskeletal complications. The main aim of this review is the update of the latest information concerning cardiovascular comorbidities in patients with acromegaly.State of knowledge: Studies revealed that 80% of acromegalic patients will develop cardiovascular comorbidities. Complications such as: hypertension, cardiomyopathy, arrhythmia, heart valve disease, atherosclerosis and coronary heart disease as well as myocardial infarction were the most widely described. They are responsible for 44% of deaths in the first decade of the acromegaly and 23% in the second one.Conclusions: Because of the delayed diagnosis of acromegaly in most patients, most comorbidities are discovered in advanced stages leading to the decrease in patients’ life span. Adequate knowledge about potential complications is necessary to increase patients’ quality of lives

Bipolar Androgen Therapy in the management of prostate cancer

Introduction and purpose: Prostate cancer (PCa) as one of the most frequent neoplasms in men remains a challenge for oncologists. The main strategy of its treatment is the Androgen Deprivation Therapy (ADT) the principle of which is an inducement of hypogonadism. The lack of testosterone is not only a factor greatly contributing to a decrease of quality of life overall, but additionally it increases the odds of the complications, including low libido and erectile disfunction, metabolic abnormalities, high cardiovascular risk, osteoporosis, anaemia, or depression. ADT also has the potential of inducement of castration resistance (CRPC), which significantly worsen patients prognosis. The main purpose of this review is to explore the Bipolar Androgen Therapy (BAT), which has the potential to solve the aforementioned problems. State of knowledge: The mechanism of BAT action has been described. BAT is effective not only against CRPC, but androgen-dependant PCa as well. BAT reverses the hormone resistance in CRPC, thus allowing the rechallenging of the ADT. It has the direct cytotoxic effect on cancer cells. Additionally BTA increases the exponents of the general quality of life of the patients. There is a number of active clinical trials regarding BAT. Conclusions: BAT is a safe therapeutic strategy with the high efficacy in reversing hormone resistance in CRPC patients, thus significantly increasing their health prognoses and it allows to alleviate or avoid the adverse effects of ADT

The gut microbiota and mental health

INTRODUCTION AND PURPOSE Recent studies have shown that changes in the microbiome, probiotic and antibiotic supplementation, can significantly modulate various forms of neuropsychiatric disorders - such as depression, anxiety and stress-related disorders. There is growing body of evidence pointing to a bidirectional correlation along the brain-gut microbiota line. This axis is connected through endocrine, immune and neuronal pathways. The nerves that make up the enteric nervous system transmit modifications occurring in the gastrointestinal tract and through the vagus nerve to the central nervous system (1). The main purpose of this review is to update recent information on the correlation between the gut microbiota and mental health. STATE OF KNOWLEDGE Interactions between the gastrointestinal system and brain function have become an important field of psychiatric research in recent years. Probiotics are thought to be a potentially valuable player in the treatment of many neuropsychiatric disorders. However, the role of specific gut microbiota species in the development of these disorders remains unclear. CONCLUSIONS Increasing knowledge of the correlation between gut microbiota and mental health may improve the quality of treatment for patients with neuropsychiatric conditions. Further research on larger groups is needed to assess whether probiotics can modify altered psychological well-being and be integrated into current, conventional treatments.INTRODUCTION AND PURPOSE Recent studies have shown that changes in the microbiome, probiotic and antibiotic supplementation, can significantly modulate various forms of neuropsychiatric disorders - such as depression, anxiety and stress-related disorders. There is growing body of evidence pointing to a bidirectional correlation along the brain-gut microbiota line. This axis is connected through endocrine, immune and neuronal pathways. The nerves that make up the enteric nervous system transmit modifications occurring in the gastrointestinal tract and through the vagus nerve to the central nervous system (1). The main purpose of this review is to update recent information on the correlation between the gut microbiota and mental health. &nbsp;STATE OF KNOWLEDGE Interactions between the gastrointestinal system and brain function have become an important field of psychiatric research in recent years. Probiotics are thought to be a potentially valuable player in the treatment of many neuropsychiatric disorders. However, the role of specific gut microbiota species in the development of these disorders remains unclear. CONCLUSIONS Increasing knowledge of the correlation between gut microbiota and mental health may improve the quality of treatment for patients with neuropsychiatric conditions. Further research on larger groups is needed to assess whether probiotics can modify altered psychological well-being and be integrated into current, conventional treatments

Rewiring Neural Interactions by Micro-Stimulation

Plasticity is a crucial component of normal brain function and a critical mechanism for recovery from injury. In vitro, associative pairing of presynaptic spiking and stimulus-induced postsynaptic depolarization causes changes in the synaptic efficacy of the presynaptic neuron, when activated by extrinsic stimulation. In vivo, such paradigms can alter the responses of whole groups of neurons to stimulation. Here, we used in vivo spike-triggered stimulation to drive plastic changes in rat forelimb sensorimotor cortex, which we monitored using a statistical measure of functional connectivity inferred from the spiking statistics of the neurons during normal, spontaneous behavior. These induced plastic changes in inferred functional connectivity depended on the latency between trigger spike and stimulation, and appear to reflect a robust reorganization of the network. Such targeted connectivity changes might provide a tool for rerouting the flow of information through a network, with implications for both rehabilitation and brain–machine interface applications

Joint reconstruction of galaxy clusters from gravitational lensing and thermal gas I. Outline of a non-parametric method

We present a method to estimate the lensing potential from massive galaxy clusters for given observational X-ray data. The concepts developed and applied in this work can easily be combined with other techniques to infer the lensing potential, e.g. weak gravitational lensing or galaxy kinematics, to obtain an overall best fit model for the lensing potential. After elaborating on the physical details and assumptions the method is based on, we explain how the numerical algorithm itself is implemented with a Richardson-Lucy algorithm as a central part. Our reconstruction method is tested on simulated galaxy clusters with a spherically symmetric NFW density profile filled with gas in hydrostatic equilibrium. We describe in detail how these simulated observational data sets are created and how they need to be fed into our algorithm. We test the robustness of the algorithm against small parameter changes and estimate the quality of the reconstructed lensing potentials. As it turns out we achieve a very high degree of accuracy in reconstructing the lensing potential. The statistical errors remain below 2.0% whereas the systematical error does not exceed 1.0%.Comment: 7 pages, 5 figures. To appear in A&

Reconstructing the projected gravitational potential of galaxy clusters from galaxy kinematics

We develop a method for reconstructing the two-dimensional, projected gravitational potential of galaxy clusters from observed line-of-sight velocity dispersions of cluster galaxies. It is the third of an intended series of papers aiming at a unique reconstruction method for cluster potentials combining lensing, X-ray, Sunyaev-Zel'dovich and kinematic data. The observed galaxy velocity dispersions are deprojected using the Richardson-Lucy algorithm. The obtained radial velocity dispersions are then related to the gravitational potential by using the tested assumption of a polytropic relation between the effective galaxy pressure and the density. Once the gravitational potential is obtained in three dimensions, projection along the line-of-sight yields the two-dimensional potential. For simplicity we adopt spherical symmetry and a known profile for the anisotropy parameter of the galaxy velocity dispersions. We test the method with a numerically simulated galaxy cluster and galaxies identified therein. We extract a projected velocity-dispersion profile from the simulated cluster and pass it through our algorithm, showing that the deviation between the true and the reconstructed gravitational potential is less then 10% within approximately 1.2 Mpc/h from the cluster centre.Comment: 8 pages, submitted to A&