1,720,964 research outputs found
Mass dependent corrections of the orbital period of a planet
No full textThis paper has a didactic aim. Indeed, starting from the well-known principle of free fall discovered by Galileo Galilei, we want to make some reflections that we consider useful for secondary school students. Being the acceleration invariant with respect to Galilei's transformations, it is useful to underline that the free fall in a gravitational field is independent of the mass of the body that falls only if the attractive mass is an inertial frame. In general, the corrections to the motion of a test particle falling in a gravitational field due to its mass can be easily calculated avoiding misinterpretations of Galileo's principle. Moreover, it may be useful to observe that, in the case of periodic motions, these corrections increase with time and would lead, over the centuries, to not negligible effects
Unruh temperature with maximal acceleration
No full textIn this paper, we modify the geometry of Rindler space so as to include an upper limit on the acceleration. Caianiello and his collaborators, in a series of papers, have analyzed the corrections to the classical spacetime metrics due to the existence of a maximal acceleration. Our goal is to derive, in this context, in a very simple way, the so-called Unruh temperature
A determination of the Ω_0m h^2 cosmological parameter without “tension”
No full textMeasurements for the expansion rate of the universe disagree. Indeed, local measurements suggest a higher value of the Hubble constant than those performed through the cosmic microwave background. This fact led to a very interesting debate within the scientific community. The paper is not devoted to give solutions to the problem of "Hubble tension". The aim of this paper is, on the contrary, to deduce the Omega(0m)h(2) cosmological parameter from a theoretical point of view, using only two experimental data: the temperature of CMB today and the temperature of photons near the decoupling time
Rotation induced in a coil moving in an electric field
No full textThe integral form of the fourth Maxwell’s equation is often written in two different ways: in the first, the partial derivative of Electric field appears, while the second contains a time derivative of electric flux integral. It would be useful, from a didactic point of view, to discriminate between the two different interpretations. In this paper, starting from a previous work about Faraday’s law, we analyze the derivative of the flux of the electric field and we shed light on the right way to write the Maxwell equations. We introduce a “magnetomotive force” and we find, from the corresponding generalization of the second Laplace’s law, the effect of a rotation induced in a coil embedded in an electric field
On the velocity of a quantum particle in the de Broglie–Bohm quantum mechanics: the case of the bouncing ball
Full text linkStarting from the dynamics of a bouncing ball in classical and quantum regime, we suggest a modification of the probability current in quantum mechanics. We consider the consequences of this generalization on the resulting velocity of a quantum particle in the de Broglie–Bohm interpretation of quantum mechanics
Spreading of Covid-19 in Italy as the spreading of a wave packet
No full textWe find that the spreading of the COVID-19 pandemic in Italy can be described
as the propagation of a wave packet in a dispersive medium where the effect of lockdown is
simulated by the dispersion relation of the medium. We start expanding a previous statistical
analysis based on the official data provided by the Italian Civil Protection during 100 days,
from March 2nd to June 9th. As the total number of people infected with the virus is uncertain,
we have considered the trend of ICU patients and the sum of hospitalized patients and
the deceased. Both the corresponding curves are well approximated by the same function
depending on four free parameters. The model allows to predict the short-term behavior of
the pandemic and to estimate the benefits due to lockdown measures
Twin paradox in curved spacetime
No full textThe twin paradox has played an important role in the history of special relativity (SR). A precise calculation would require the application of the general theory of relativity (GR) but, neglecting the acceleration phases of the traveling twin, even in SR it is possible to find the correct solution without logical contradictions. Nowadays it is well known that the twin thought experiment seems a paradox as a consequence of a naive application of time dilation and the principle of relativity. The twin who goes on space travel is the one who, returning to the twin at rest, finds the aged brother. Continuing in this pedagogical tradition, we want to add a further consideration. In fact, the experiment has always been explained by considering the two twins immersed in Minkowski’s spacetime. It could be interesting, from a didactic point of view, to analyze the same thought experiment without neglecting the Earth’s gravitational field. Indeed, under certain conditions, it may happen that the traveling brother can grow older than his brother at res
The Effect of Interplay between the Newtonian Gravitational Field and the Cosmological Expansion
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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