Catégorie

Physical cosmology

La cosmologie quantique est une branche spéculative de la cosmologie qui vise à décrire les premiers instants de l'Univers en le considérant comme un objet quantique, c'est-à-dire décrit par les lois de la mécanique quantique et de la théorie quantique des champs. Cette discipline peut être vue comme une branche de la gravité quantique, quoique la connaissance d'une théorie quantique de la gravitation ne soit pas indispensable pour certains résultats de la cosmologie quantique. L'idée d'utiliser un formalisme basé sur une fonction d'onde pour décrire l'Univers tout entier repose sur des travaux de John Wheeler et Bryce DeWitt à la fin des années 1960 (voir Équation de Wheeler-DeWitt). Le sujet s'est surtout développé à partir des années 1980, en particulier grâce aux travaux de Jim Hartle et Stephen Hawking.

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Exercices associés (32)

Problème à deux corps, centre de masse

We consider a square plate with side of length a and uniform density. We pierce a circular hole of radius R in the plate such that the distances between the hole’s edge and two adjacent edges of the plate are b and c, with b,u2006cu2004

Cylindre creux: moment d inertie

xa0 Calculate the moment of inertia of a hollow cylinder of width e and mass M with respect to its revolution axis. We remind the moment of inertia of a full cylinder of mass M₁ :

I_{Oz} = \frac{1}{2}M_1R^2

. xa0 Density of material:

\rho \Rightarrow \rho = \frac{M}{V}

V = \underbrace{h\pi R^2}_{V_1} - \underbrace{h\pi (R - e)^2}_{V_2}

V₁ volume of the external cylinder, V₂ volume of the "hole" I_(Oz)u2004=u2004I_(Oz)¹u2005−u2005I_(Oz)² Moment of inertie of the full cylinder - Moment of inertia o

La grosse Bertha

Big Bertha was a large canon cannon of mass M that fired projectiles of mass m over very large distances d (n.b. range on the ground). Compute the kinetic energy K that its damping device had to absorb each time a projectile was fired. Numerical application:

Canon mass: Mu2004=u200410′000u2006kg,
Projectile mass: mu2004=u200410u2006kg,
Firing distance: du2004=u200440u2006km.
Conservation of momentum: Before the shot, the system composed of the cannon and the projectile is at res

Chute libre près de la Terre

On the Earth, which has radius R_(T) and mass M_(T), a marble of mass m is dropped with no initial speed from a height z(t=0)u2004=u2004H above ground. The gravitational force acting on the marble is given by the universal gravitational law. We neglect air friction.

Write the marble’s equation of motion.
Integrate the equation of motion to find the expression for the mechanical energy. Use the initial conditions to find the integration constant.
What’s the marble’s speed when it reach

Le corbeau et le renard

A few days after the events narrated in the famous fable[1], the crow and the fox meet again. Having learned from its mistakes, the crow is determined not to be fooled again by the fox’s flattery. The fox, however, is set on getting a second piece of cheese. This time , it chooses a more direct method and throws a stone at the crow to scare it. It works beyond expectations: as soon as the stone is thrown, the crow drops the cheese. The crow is perched on a tree of height H; the fox is a distance L from the

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Notebooks associés (9)

Ewald Sphere

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Ewald Sphere¶{.anchor-link} {#Ewald-Sphere}

Play with the Ewald Sphere This schematics represent the Ewald sphere for a typical high

Estimation of Electron Density and Mean Free Time for Transparent Conductors

Chapter 1: Transparent Conductors[1]¶ Instruction: The purpose of this notebook is to try and find values of electron density and mean free time for a material suitable to be used as a transparent conductors. The final estimate should be the order of the two parameters to be used[2]¶ In [1]: import numpy as np from bokeh.io import push_notebook, output_notebook, show from bokeh.layouts import row, column from bokeh.plotting import figure output_notebook() from ipywidgets import interact from collect

Interactive Phonon Band Structure Visualization

In [1]: import numpy as np import matplotlib.pyplot as plt from matplotlib import animation from matplotlib import rc import ipywidgets as ipw from ipywidgets import interact,interactive import ipywidgets as widgets from IPython.display import HTML %matplotlib widget global global_K1 global global_K2 global global_branche global global_selected_k In [2]: def get_closest_point(clic_x,clic_y): # Get the data from the figure ax= plt.gca() # get axis handle acoustic_data = ax.lines[1] op

Whistle-Activated Keylock System Implementation

Whistling Keylock[1]¶ In this notebook we will implement a simple "whistle-activated" keylock, that is, an access control system where the password is a pre-defined melody. To program the lock, you record your musical passphrase and then, to open the lock, you whistle it back. Although the implementation will be simple and skip most of the fine details that would be necessary to produce a truly robust system, we need to take into account at least the following points: * The syste

Simulating Electron Motion in 2D Materials Using the Drude Model - Basic

Drude model considers electrons small solid particles traveling through lattices as a stationary array of heavier and bigger atoms. The model use "mean free time" as a measure of the frequency an electron gets scattered. This jupyter notebook makes use of this concept and uses stochastic method to simulat electrons traveling through a 2D material of finite width but infinite length."

"#### First we setup the simulation parameters such as the external electric field, number of electrons (default

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Exercices associés (32)

Problème à deux corps, centre de masse

Cylindre creux: moment d inertie

xa0 Calculate the moment of inertia of a hollow cylinder of width e and mass M with respect to its revolution axis. We remind the moment of inertia of a full cylinder of mass M₁ :

I_{Oz} = \frac{1}{2}M_1R^2

. xa0 Density of material:

\rho \Rightarrow \rho = \frac{M}{V}

V = \underbrace{h\pi R^2}_{V_1} - \underbrace{h\pi (R - e)^2}_{V_2}

V₁ volume of the external cylinder, V₂ volume of the "hole" I_(Oz)u2004=u2004I_(Oz)¹u2005−u2005I_(Oz)² Moment of inertie of the full cylinder - Moment of inertia o

La grosse Bertha

Canon mass: Mu2004=u200410′000u2006kg,
Projectile mass: mu2004=u200410u2006kg,
Firing distance: du2004=u200440u2006km.
Conservation of momentum: Before the shot, the system composed of the cannon and the projectile is at res

Chute libre près de la Terre

Write the marble’s equation of motion.
Integrate the equation of motion to find the expression for the mechanical energy. Use the initial conditions to find the integration constant.
What’s the marble’s speed when it reach

Le corbeau et le renard

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Physical cosmology

Chattez avec Graph Search

Ewald Sphere¶{.anchor-link} {#Ewald-Sphere}

Ewald Sphere¶{.anchor-link} {#Ewald-Sphere}

Euclid: Field-level inference of primordial non-Gaussianity and cosmic initial conditions

The impact of spectroscopic redshift errors on cosmological measurements

A comprehensive separation of dark matter and baryonic mass components in galaxy clusters – II: an overview of the mass distribution in Abell S1063