# old_wiki

## AI books

Neural Networks Artificial Intelligence Collective Intelligence Swarm Intelligence Data Mining Pattern Recognition All the links above are generated using the trick to ask google scholar something like “book [topic]” where [topic] is the topic you are interested in.

## Basic ideas of general relativity

General Relativity (GR) is a classical field theory (whatever that means, could be something like Electrodynamics or something like Fluiddynamics) There is no gravitational force. Principle of Mach: The distribution of matter and energy defines the geometry of space-time Principle of Equivalence: Acceleration = homogenous (in time and space) gravitational field; Principle of Covariance: All coordinate systems are equal. The equations of physics should have the same form in all coordinate systems.

## Battery

Lithium metal-air batteries can store a tremendous amount of energy–in theory, more than 5,000 watt-hours per kilogram. That’s more than ten-times as much as today’s high-performance lithium-ion batteries, and more than another class of energy-storage devices: fuel cells. Instead of containing a second reactant inside the cell, these batteries react with oxygen in the air that’s pulled in as needed, making them lightweight and compact. Bibliography IBM Invests in Battery Research Lithium-Luft-Batterien für Elektroautos Air-fuelled Battery Could Last Up to 10 Times Longer Lithium Oxygen Battery

## Can a computer ask questions

Computers are useless. They can only give you answers. (Pablo Picasso) Is Picasso correct? In the scientific literature the question if a computer can be made to ask questions is hardly discussed. However literature containing the following terms implicitly discusses this topic: Unsupervised learning Semi-supervised learning Active learning Bibliography [http://evanjones.ca/picasso.html] Olsson (2009) : A literature survey of active machine learning in the context of natural language processing Castro et al.

## Classical limit of quantum mechanics

The semi-classical limit corresponds to $h\rightarrow 0$, which can be seen to be equivalent to $m\rightarrow\infty$ , the mass increasing so that it behaves classically. (from http://en.wikipedia.org/wiki/Dynamical_billiards ) An increasing mass can be seen as an increase in the number $N$ of involved particles with mass $m_0$. So is the limit of a $N$-particle quantum system for $N\rightarrow\infty$ a classical system?

## Data Mining Algorithms

Bibliography Wu (2008):Top 10 algorithms in data mining Segaran (2007): Programming Collective Intelligence: Building Smart Web 2.0 Applications

## Fluid Dynamics of Spacetime

Bibliography Christopher Eling (2008) : Hydrodynamics of spacetime and vacuum viscosity Christopher Eling et al. (2006) : Non-equilibrium Thermodynamics of Spacetime Ted Jacobson (1995) : Thermodynamics of Spacetime: The Einstein Equation of State

## Graphs in SQL databases

SQL Graphs in the database: SQL meets social networks – techPortal Working with Graphs in MySQL Graph database Social networks in the database: using a graph database Neo4j - a Graph Database that Kicks Buttox Large-scale Graph Computing at Google

The basic equations are: $$G_{\mu \nu} + \Lambda g_{\mu \nu}= \frac{8\pi G}{c^4} T_{\mu \nu}$$ with $$G_{\mu\nu} = R_{\mu\nu} - \frac{1}{2} g_{\mu\nu}R$$ and $$T_{\mu \nu} = g_{\mu \alpha} g_{\nu \beta} T^{\alpha \beta}$$ and $$T^{\alpha \beta} \, = \left(\rho + \frac{p}{c^2}\right)u^{\alpha}u^{\beta} + p g^{\alpha \beta}$$ Eq.([[eref field]]) is the famous Einstein field equation connecting the Einstein tensor ([[eref ein]]) with the energy-momentum tensor ([[eref energy]]). The energy-momentum tensor in the form here is the stress-energy tensor of fluid (and I think this is the form Einstein used originally) and basically represent the relativistic euler equations.