Letteratura scientifica selezionata sul tema "DARK ENERGY PHENOMENA"

We study the behavior of the vacuum condensates characterizing many physical phenomena. We show that condensates due to thermal states, to fields in curved space, and to neutrino mixing, may represent new components of the dark matter, whereas the condensate due to axion-photon mixing can contribute to the dark energy. Moreover, by considering a supersymmetric framework, we show that the nonzero energy of vacuum condensates may induce a spontaneous supersymmetry breaking.

It is shown that the vacuum condensate induced by many phenomena behaves as a perfect fluid which, under particular conditions, has zero or negative pressure. In particular, the condensates of thermal states of fields in curved space and of mixed particles have been analyzed. It is shown that the thermal states with the cosmic microwave radiation temperature and the Unruh and the Hawking radiations give negligible contributions to the critical energy density of the universe, while the thermal vacuum of the intercluster medium could contribute to the dark matter, together with the vacuum energy of fields in curved space-time and of mixed neutrinos. Moreover, a component of the dark energy can be represented by the vacuum of axion-like particles mixed with photons and superpartners of neutrinos. The formal analogy among the systems characterized by the condensates can open new scenarios in the possibility of detecting the dark components of the universe in table top experiments.

We consider Little Rip (LR) and Pseudo Rip (PR) cosmological models with two interacting ideal fluids, corresponding to dark energy and dark matter. The interaction between the dark energy and the dark matter fluid components is described in terms of the parameters in the equations of state for the LR and PR universes. In contrast to a model containing only a pure dark energy, the presence of the interaction term between the fluid components in the gravitational equations leads to a modification of the equation of state parameters. The properties of the early universe in this formalism are pointed out.

In a recently published paper called Nexus: A quantum theory of space-time, gravity and the quantum vacuum by the above author, a plausible self-consistent quantum theory of space-time, gravity and the quantum vacuum is provided. In this current paper the author focuses primarily on the graviton as described in Nexus as a solution to the enigmatic phenomena of Dark Energy and Dark Matter as well as includes corrections to the first paper.

In this paper we review a part of the approaches that have been considered to explain the extraordinary discovery of the late time acceleration of the Universe. We discuss the arguments that have led physicists and astronomers to accept dark energy as the current preferable candidate to explain the acceleration. We highlight the problems and the attempts to overcome the difficulties related to such a component. We also consider alternative theories capable of explaining the acceleration of the Universe, such as modification of gravity. We compare the two approaches and point out the observational consequences, reaching the sad but foresightful conclusion that we will not be able to distinguish between a Universe filled by dark energy or a Universe where gravity is different from General Relativity. We review the present observations and discuss the future experiments that will help us to learn more about our Universe. This is not intended to be a complete list of all the dark energy models but this paper should be seen as a review on the phenomena responsible for the acceleration. Moreover, in a landscape of hardly compelling theories, it is an important task to build simple measurable parameters useful for future experiments that will help us to understand more about the evolution of the Universe.

The phenomena customarily described with the standard ΛCDM model are broadly reproduced by an extremely simple model in TeVeS, Bekenstein's1 modification of general relativity motivated by galaxy phenomenology. Our model can account for the acceleration of the Universe seen at SNeIa distances without a cosmological constant, and the accelerations seen in rotation curves of nearby spiral galaxies and gravitational lensing of high-redshift elliptical galaxies without cold dark matter. The model is consistent with BBN and the neutrino mass between 0.05 eV to 2 eV. The TeVeS scalar field is shown to play the effective dual roles of dark matter and dark energy, with the amplitudes of the effects controlled by a μ function of the scalar field, called the μ essence here. We also discuss outliers to the theory's predictions on multiimaged galaxy lenses and outliers on the subgalaxy scale.

We argue that dark matter (DM)and dark energy phenomena associated with galactic rotation curves (RC’s), X-ray cluster mass profiles, and type Ia supernova data can be accounted for via small corrections to idealized general relativistic spacetime geometries due to disordered locality. Accordingly, we fit the HI nearby galaxy survey (THINGS) RC data rivaling modified Newtonian dynamics, Roentgen Satellite/Advanced Satellite for Cosmology and Astrophysics (ROSAT/ASCA) X-ray cluster mass profile data rivaling metric-skew-tensor gravity, and SCP Union2.1 SN Ia data rivaling [Formula: see text]CDM without nonbaryonic DM or a cosmological constant. In the case of DM, we geometrically modify proper mass interior to the Schwarzschild solution. In the case of dark energy, we modify proper distance in Einstein–de Sitter cosmology. Therefore, the phenomena of DM and dark energy may be chimeras created by an errant belief that spacetime is a differentiable manifold rather than a disordered graph.

The mystery associated with a proposed Dark Sector of phenomena that are separate from the standard model of particle physics is described. A Dark Sector may possess matter particles, force carriers which mediate their interactions, and new interactions and symmetries that are beyond the standard model of particle physics. Various approaches for Dark Sector searches are described, including those at the energy frontier at the Large Hadron Collider, in astrophysical interactions with both terrestrial experiments and those in space-born platforms. Searches using low energy photons from microwave energies in cryogenic environments to x-ray energies are also described. While there is no noncontroversial evidence for Dark Sector phenomena presently, new searches with more modern equipment and analysis methods are exploring regions of phase space that have not been available before now, indicating ongoing interest and excitement in this research.

In the thesis, we have carried out a dark energy phenomena of the Universe which has been predicted by many cosmological observations. In chapter 2, we have studied HDE model in well motivated and established BD theory. We have assumed a logarithmic form of BD scalar field, proposed by Kumar and Singh [181]. We have extended our study to HDE model with future event horizon as an IR cutoff and have shown that this model explains the evolution and solve the coincidence problem more effectively with the logarithmic form of BD scalar field in comparison of power-law form. In chapter 3, the concept of bulk viscosity with new HDE has been analysed to explain the recent accelerated expansion of the Universe. It is thought that the negative pressurecausedbythebulkviscositycanplaytheroleofdarkenergycomponentand drive the accelerated expansion of the Universe. We have observed that the accelerated expansion may be possible for non-viscous case but the phase transition is not possible. It has been tried to demonstrate that the bulk viscosity can play the role as a possible candidate of dark energy. Using statefinder parameters and Om diagnostic, it has been found that our model shows the similar behavior as quintessence model and Chaplygin gas model for different values of the viscosity coefficient. Chapter4istheextensionoftheworkcarriedoutinchapter3, in f(R,T) gravitytheory. We have studied new HDE model with constant bulk viscosity in f(R,T) gravity theory. We have observed that the accelerated expansion may be possible for nonviscouscasein f(R,T) gravitybutdoesnotshowphasetransition. Theintroductionof bulk viscosity not only makes the phase transition possible but also presents a wide range of possible evolutions of the Universe depending on parameters of the model. We have also distinguished this model from other existing dark energy models using two geometrical diagnostics: statefinder parameter and Om diagnostic. The ther 163 164 modynamics and the local entropy have been discussed for this model. The model preserves the validity of the second law of thermodynamics as bulk viscous coefficient remains positive through the evolution of the Universe. Big-Rip and Type III singularities are obtained depending on values of model parameter. In chapter 5, we have generalised the previous work for more general form of the bulk viscous coefficient with new HDE in the framework of f(R,T) gravity theory. We have classified all possible scenarios (deceleration, acceleration and their transition) with different parameter regions chosen properly for positive and negative ranges of model parameter and viscosity coefficients to analyze the evolution of the Universe. WehavealsoinvestigatedthestatefinderpairandOmdiagnosticforthisviscousmodel to discriminate from other existing DE models. The model evolution behaviors are shown by plotting the statefinder and Om−z trajectories. The evolution of effective EoS parameter is also shown graphically. The entropy and generalized second law of thermodynamics are found to be valid for this model under some constraints on bulk viscous coefficients. Thus,wehaveobservedthatGTRaswellas f(R,T) gravityhavepotentialtoexplain therecentacceleratedexpansionoftheUniverseinthepresenceofbulkviscositywith new HDE. The concept of bulk viscosity presents a mechanism to observe accelerated expansion as well as phase transition of the Universe. The spatially homogeneous and anisotropic Bianchi-I and Bianchi-V models with the scalar field have been studied in the chapter 6 and 7. In chapter 6, we have investigated the effect of non-interacting scalar field in the framework of Bianchi-I. We have assumed the average scale factor as an exponential function of scalar field. We have considered the solution for two cases: flat potential and exponential potential. We have obtained that the zero-rest-mass model expands with decelerated rate and behaves like a stiff matter. In case of exponential potential function, the model expands with decelerated, accelerated or shows the transition depending on the model parameters. The isotropization is observed at late-time evolution of the Universe in exponential potential model. Chapter7istheextensionofthepreviouschapterforhomogeneousandanisotropic Bianchi-V model filled with perfect fluid and scalar field. The two sources have been assumed to be non-interacting. The average scale factor and scalar potential have been considered as an exponential functions of the scalar field. The observational data has been used here to find out the values of model parameters. The model 165 behaves like ΛCDM or SCDM depending on the values of model parameters. The anisotropic models explains that in late time of evolution the anisotropic behaviour is damped out and the Universe become isotropic one which is the good harmony with the current observational data.

Prekladaný vysokoškolský učebný text „Bioenergetika“ by mal slúžiť ako úvod do problematiky štúdia v oblasti bioenergetiky. Táto vedná oblast je v súčasnosti vysoko aktuálna, pretože výsledky získané bioenergetickým výskumom v uplynulých rokoch zreteľne ukazujú, že bioenergetické procesy prebiehajúce v živých systémoch neslúžia “len” na transformáciu energie, ale ovplyvňujú aj priebeh procesov ako sú apoptóza, starnutie, vznik a rozvoj mnohých ochorení (predovšetkým neurodegeneratívnych). Tieto skutočnosti jednoznačne naznačujú potrebu existencie kvalitných učebných textov, ktoré by prijateľným spôsobom umožnili študentom získať potrebné informácie a vedomosti v tejto vednej discipline. Z vyššie uvedených dôvodov sme sa rozhodli vytvoriť tieto učebné texty, ktoré sú vo forme desiatich samostatných kapitol, ktoré však na seba prirodzene a logicky nadväzujú. Jedna kapitola predstavuje v podstate jednu prednášku v rámci kurzu Bioenergetiky, ktorý je realizovaný na Prírodovedeckej fakulte Univerzity Pavla Jozefa Šafárika v Košiciach na magisterskom a doktorandskom stupni študijného programu „Biofyzika“. Zároveň tieto texty môžu poslúžiť aj pri výučbe v študijnom predmete Biochémia, ktorý je prednášaný v bakalárskych a magisterských stupňoch študijných programov “Biochémia” resp. “Biofyzika”. Dovoľujeme si vyjadriť presvedčenie, že tieto učebné texty by mohli byť istým spôsobom nápomocné aj vedeckým pracovníkom pracujúcim v oblasti výskumu týkajúcho sa problematiky transformáci energie v biologických organizmoch a fenoménoch spojených s touto transformáciou. V týchto učebných textoch sú postupne uvádzané poznatky týkajúce sa základných konceptov bioenergetiky, mechanizmov procesov ako sú glykolýza a Krebsov cyklus (okrem podrobného a uceleného popis týchto procesov je tu uvedený aj všeobecný náhľad o prepojenosti týchto procesov ako aj ich začlenenie do kompaktného pohľadu na celkový proces transformácie energie v biologických organizmoch), zloženia štruktúry a funkčnosti biologických membrán (táto oblast je nevyhnutná pre lepšie pochopenie poznatkov, ktoré sú uvedené v nasledujúcich kapitolách). V nasledujúcich kapitolách sa učebný text zaoberá popisom štruktúry a funkcie mitochondrií, pričom veľký dôraz je dávaný na popis vlastností a mechanizmov fungovania štyroch komplexov dýchacieho reťazca a ATP-syntázy. Tieto komplexy vytvárajú podmienky pre existenciu “najdôležitejšieho” bioenergetického procesu, oxidatívnej fosforylácie. V záverečných dvoch kapitolách sú uvedené mechanizmy procesov vytvárajúcich fotosyntézu, jej svetlej aj tmavej fázy. Sú tu relevantné informácie o tomto “druhom” najdôležitejšom bioenergetickom procese prebiehajúcom v mnohých biologických organizmoch a poskytujúcom možnosť transformácie enrgie elektromagnetického žiarenia na energiu “ukrytú” v chemických väzbách určitých chemických molekúl. Chceme vyjadriť naše presvedčenie, že predložené učebné texty “Bioenergetika” budú dobrým “pomocníkom a inšpirátorom” pre mnohých študentov, ktorí sa budú chcieť dozvedieť čo najviac o fascinujúcich štruktúrach a mechanizmoch umožňujúcich transformáciu energie v živých systémoch, bez ktorej by nebola možná existencia života ako ho poznáme. Želáme príjemné a podnetné čítanie a štúdium. URL: www.unibook.upjs.sk The textbook "Bioenergetics" should serve as an introduction to the study of bioenergetics. This field of science is currently highly actual, as the results of the bioenergetics research in recent years clearly show that bioenergetics processes in living systems can "serve" not only to transformation of energy, but also affect the course of processes such as apoptosis, aging, origin and development of many diseases (especially neurodegenerative). These facts clearly indicate the need for the existence of quality teaching texts that would allow students to acquire the necessary information and knowledge in this scientific discipline in an acceptable way. For the above mentioned reasons, we decided to create these textbooks, which are in the form of ten chapters, which naturally and logically follow each other. One chapter basically presents one lecture within the course of Bioenergetics, which is realized at the Faculty of Science of the Pavel Jozef Šafárik University in Košice at the master's and doctoral degree of the study program "Biophysics". At the same time, these texts can also be used for teaching in the study subject Biochemistry, which is taught in the bachelor's and master's degree programs of the study programs "Biochemistry" resp. “Biophysics”. We would like to express our conviction that these textbooks could in some way also help researchers working in the field of the energy transformation in biological organisms and the phenomena associated with this transformation. These textbooks present knowledge about the basic concepts of bioenergetics, the mechanisms of processes such as glycolysis and the Krebs cycle (in addition to a detailed and comprehensive description of these processes, there is also a general view of the interconnectedness of these processes and their incorporation into a compact view of the overall energy transformation in biological organisms), the structure and functionality of biological membranes (this area is necessary for a better understanding of the knowledge presented in the following chapters). In the following chapters, the textbook deals with the description of the structure and function of mitochondria, with great emphasis on the properties and mechanisms of functioning of the four complexes of the respiratory chain and ATP-synthase. These complexes create the basis for the existence of the "most important" process in bioenergetics, oxidative phosphorylation. In the final two chapters, the mechanisms of the processes that produce photosynthesis, its light and dark phases, are presented. There is relevant information about this "second" most important bioenergetics process taking place in many biological organisms and providing the possibility of transforming the energy of electromagnetic radiation into energy "hidden" in the chemical bonds of certain chemical molecules. We want to express our conviction that the textbooks "Bioenergetics" will be a good "helper and inspirer" for many students who want to learn as much as possible about the fascinating structures and mechanisms for energy transformation in living systems, without which it would not be possible existence of life as we know it.

AbstractRadiative cooling of the interstellar medium plays a vital role in the context of galaxy formation and evolution. On the other hand, the cooling time in the high-density regions involving star formation is much shorter than the dynamical time of the gas. In numerical simulations, it is challenging to solve physical phenomena coexisting on significantly different timescales, and it is known as the overcooling problem in the study of galaxy formation. Townsend (2009) has developed the Exact Integration (EI) scheme that provides a stable solution for the cooling term in the energy equation of astrophysical fluid dynamics, regardless of the size of the simulation time step. We apply the EI scheme to define the effective cooling time that accounts for the temperature dependence of the cooling rate and investigate the thermodynamic evolution of gas in colliding dark matter subhalos. The results show that the conventional cooling time always indicates a shorter than the effective cooling time derived by the EI scheme because it does not include the dependence of the cooling rate on temperature. Furthermore, we run three-dimensional galaxy collision simulations to examine the difference in thermodynamic evolution between the EI scheme and the conventional Crank–Nicholson method for solving the cooling equation. Comparing the results of the two simulations, we find that the EI scheme suppresses the rapid temperature decrease after galaxy collisions. Thus, the EI scheme indicates considerable potential for solving the overcooling problem in the study of galaxy formation.

AbstractHuman trust can be construed as a heuristic wager on the predictability and benevolence of others, within a compatible worldview. A leap of faith across gaps in information. Generally, we posit that trust constitutes a functional bridge between individual and group homeostasis, by helping minimize energy consumed in continuously monitoring the behavior of others and verifying their assertions, thus reducing group complexity and facilitating coordination. Indeed, we argue that trust is crucial to the formation and maintenance of collective entities. However, the wager that trust represents in the face of uncertainty leaves the possibility of misallocated trust, which can result in maladaptive outcomes for both individuals and groups. More specifically, trust can be thought of as a scale-invariant property of minimizing prediction error within ascending levels of social hierarchy ranging from individual brains to dyads, groups and societies, and ultimately civilizations. This framework permits us to examine trust from multiple perspectives at once, relating homeostasis, subjective affect and predictive processing/active inference at the individual level, with complexity and homeostasis at the collective level. We propose trust as a paradigmatic instance of an intrinsically dialectical phenomenon bridging individual and collective levels of organization, one that can be observed in daily experience and empirically studied in the real world. Here, we suggest collective psychophysiology as a promising paradigm for studying the multiscale dynamics of trust. We conclude with discussing how our integrative approach could help shine light on not only the bright but also the dark sides of trust.

Supersymmetry has been proposed, in particular as a principle to solve the so-called fine-tuning problem in particle physics by relating the masses of scalar particles (like Higgs fields) to those of fermions, which can be protected against ‘large’ mass renormalization by chiral symmetry. However, supersymmetry is, at best, an approximate symmetry broken at a scale beyond the reach of a large hadron collider (LHC), because the possible supersymmetric partners of known particles have not been discovered yet (2020) and thus, if they exist, must be much heavier. Exact supersymmetry would also have implied the vanishing of the vacuum energy and thus, of the cosmological constant. The discovery of dark energy has a natural interpretation as resulting from a very small cosmological constant. However, a naive model based on broken supersymmetry would still predict 60 orders of magnitude too large a value compared to 120 orders of magnitude otherwise. Gauging supersymmetry leads naturally to a unification with gravity, because the commutators of supersymmetry currents involve the energy momentum tensor. First, examples of supersymmetric theories involving scalar superfields, simple generalizations of supersymmetric quantum mechanics (QM) are described. The new feature of supersymmetry in higher dimensions is the combination of supersymmetry with spin, since fermions have spins. In four dimensions, theories with chiral scalar fields and vector fields are constructed.

These lectures aim to explain how certain types of atomic, molecular, and optical physics experiments can have a substantial impact in modern particle physics. A central pedagogical goal is to describe, using only concepts familiar to atomic experimentalists, how new particles can lead to new terms in the atomic or molecular Hamiltonian. Well-motivated examples are discussed, including potential dark matter candidates known as “dark photons”, known and as-yet unknown Higgs bosons, and supersymmetric particles leading to CP violation. The observable effects of new Hamiltonian terms associated with these phenomena are worked out, and state-of-the-art strategies for detecting them, using atomic and molecular experiments, are described for some cases. Remarkably, the sensitivity of atomic/molecular experiments can make it possible to detect new particles even more massive than those that can be created directly at the largest high-energy colliders.

We present a new model of cosmology based on the idea that the curvature of the universe varies with time. This model predicts a present-day exponential acceleration of the expansion of the universe without reference to a cosmological constant. We propose a new model of nucleosynthesis that accounts for the existence of cosmic structures, provides a solution to the matter/antimatter asymmetry problem, and explains the origin of the CMB. We show that this process was regulated by a vacuum imprint that came into existence during an initial Planck era inflation. One consequence is that all cosmic structures came into their final form with their present-day mass more or less simultaneously at a time of about 3×1016s. This explains the recent findings by the James Webb telescope of very large galaxies dating from that epoch. We show that the stability of galaxies and galaxy clusters demands that all galaxies must have developed supermassive black holes at that time. We go on to show that the phenomena attributed to dark matter are actually consequences of vacuum energy, that the conventional model for the CMB spectrum is wrong and finally, we resolve the Hubble tension problem.

This chapter points out the central role that gravity plays in everything that happens in the universe, which is necessary to know to understand the dark matter story. The chapter covers the relationship among mass, weight, and energy, Isaac Newton's law of gravitation, and distance scales in the universe. It also includes that mass, weight, and energy have precise meanings and are necessary for understanding how gravity works. The chapter delves into how Newton's law of gravitation exerts forces on distant objects, which will be essential for understanding how dark matter is known. It talks about the typical sizes and separations of planets, stars, and galaxies in the expanding universe and describes the redshift phenomenon, which is crucial for measuring velocities in the cosmos.

In this chapter I use the concepts of dark matter/energy and diffraction, to develop a performative hauntology of the criminological unseen/un-scene. It makes both an ontological and epistemological contribution to the emerging sub-field of ghost criminology,” and introduces a mode of analysis that can grasp spectralities as enfoldings of space-time-matter which have form, content, and power. The chapter rejects modes of inquiry that prioritize the optics of representation, reflection, and replication and offers a performative analysis that seeks out the spectral in material-discursive relations of enactment, interference, intra-/interaction, immanence, and difference. This is unpacked through a case study of 10 Rillington Place—a residential address on an ordinary street in Notting Hill, in which (at least) eight murders were committed between 1943 and 1953. A diffractive reading of this cultural bricolage asks how it animates and performs 10 Rillington Place as a material-discursive phenomenon; how the (assumed) separation of presence and absence (the organic and the spectral) is enacted in, and emergent through, a myriad of discursive, aesthetic, visual, embodied, and technological practices; and how, through a relational field of multiple lines of flight and force, the site—this site—not only comes into being, but also comes to matter.

The photochemical ring opening of 1,3-cyclohexadiene to 1,3Z,5-hexatriene is a prototype of the orbital-symmetry controlled electrocyclic reactions. In previous work [1], we studied by transient absorption spectroscopy (frequency-tripled Ti:sapphire laser around 267 nm, pulse length 250 fs, identical pump and probe wavelength) 7-dehydrocholesterol, which contains the cyclohexadiene moiety. The excited state (1B2) relaxes very rapidly (10 fs, deduced from the fluorescence quantum yield) to the 2A1 surface, which is a dark excited state and has a much lower minimum. From there, the product previtamin D is formed with a temperature independent rate within 5.2 ps. Subsequently, this primary product relaxes by rotation around a formally single bond to its stable conformer within 125 ps at room temperature (activation energy 15 kJ/mol).

An array illuminator is proposed using a phase grating in the entrance plane. The grating is illuminated uniformly and converted into the amplitude image with the help of a phase contrast setup. The conversion is brought about by a proper choice of the grating phase structure in combination with a suitable phase shift of the zero-order diffraction in the phase contrast setup. The result is a light distribution of bright areas surrounded by darkness. Since the phase grating is periodic, only one elementary cell of this grating need be considered to get the necessary condition for the phase delays in the grating and phase platelet. The compression ratio p defined as the quotient of the bright area to the cell area is limited to 1 > p ⩾ 1/4 due to the underlying two-beam interference phenomenon. Cancellation in the dark surrounding is total only in this compression range. If the total cancellation in the dark area is given up, arbitrary compression ratios can be attained although the energy concentration is limited to a factor of ~5.

Photorefractive two-beam coupling in semi-insulating GaAs (nominally undoped) is investigated as a function of temperature ranging from 77 to ~330 K. The experiment consists of two beams (pump and probe) from a cw Nd:YAG laser at 1.06 μm intersecting in a GaAs crystal and monitoring gain in the probe and loss in the pump. The intensity of each beam was ~1 W/cm2. Our results show that the coupling efficiency increases with increase in temperature and decreases with decrease in temperature. In fact, near liquid nitrogen temperature, the direction of energy coupling switches; to our knowledge, this phenomenon has not been experimentally observed. This implies that there is electron–hole competition1 in our sample. At ~330 K, the coupling efficiency increases to about twice the room-temperature efficiency; the magnitude of the change cannot be explained adequately with a single-level model. Our results extend the recent report2 where dark conduction plays a major role in a single-level single-carrier model. We also study the temperature effects on optical absorption, dark conductivity, and grating formation and erasure times. Optical absorption decreases at both lower and higher temperatures.

Regenerative pumps, also referred to as “peripheral” or “side channel” pumps, are characterized by a specific speed that contextualize them between rotary positive displacement and purely radial centrifugal pumps. Although regenerative pumps are not widely distributed, they are interesting for many industrial applications. In fact, for a given flow rate they operate at lower rotational speed with respect to purely radial pumps. Furthermore, they are less affected by mechanical problems with respect to positive displacement pumps. The energy transfer mechanism is the same of centrifugal pumps, but the presence of the side channel imposes to the fluid to pass several times through the impeller, thus obtaining higher pressure rise (as for multi-stage machines) with respect to classical purely radial pumps. Unfortunately, the complexity of the flow field, the large amount of wetted surface and a disadvantageous inflow/outflow configuration contribute to limit the maximum value of hydraulic efficiency, which is also very sensitive to the design choices. Moreover, the intrinsic complexity of the helical flow path makes the theoretical performance estimation a challenging task. It is worth underlining that an accurate performance prediction using one-dimensional models would allow to accelerate greatly the design process, with a non-negligible reduction of demanding three-dimensional Computational Fluid Dynamics (CFD) campaigns. The aim of the present work is to deeply investigate the fluid dynamics of regenerative pumps and to understand how accurately the fundamental physical phenomena can be reproduced by one-dimensional theory. To comply with these aims, a systematic post-processing of the results of several steady and unsteady three-dimensional CFD simulations is exploited for the validation of the in-house one-dimensional tool DART (Design and Analysis tool for Regenerative Turbomachinery), developed at the University of Florence. The theory underlying DART is detailed, and the assumptions of the model are verified by means of comparison with the numerical results underlining the key aspects to be considered for a reliable prediction of the pump performance.