Physical Foundations of Natural Science

1. Physical Foundations of Natural Science Vasily Beskin # 2-4

2. Gravitation and Astrophysics

3. School level Ready solutions of equations(many of which are not even formulated)

4. An example - Gravity What is the equationand that - the solution?

5. An example - Gravity What is the equationand that - the solution?

6. Scientific level The formulation of equations and their solution

7. A fundamental observation • I.Newton(1643-1722) • Our world is described by equations of the second order • Requires two initial conditions

8. Classiacal world(c, G) Fundamental generalizations Mechanics (Newton laws): Lorentz invariance, conservation laws are a consequence of the symmetry, integrated nature conservation laws, principle of least action (Lagrange) Hamiltonian formalism, from scalars to tensors.

9. Principle of least action W.Hamilton (1805-1865) J.L.Lagrange (1736-1813) coordinatexcoordinate x momentump = m vvelocity v

10. Principle of least action P.de Fermat (1601-1665) P.L.de Maupertuis(1698-1759)L.Euler (1707-1783)

11. Principle of least action Fermat's principle у x1x2 x

12. Principle of least action Action Equation of motion

13. Principle of least action The equations of motion can be derived from the principle of least (extreme) action.

14. Newton limit From school we know that

15. An example – the Gravity

16. Scalar potential • Acceleration does not dependent on the mass • The law of motion looks identical • Right to left and left to right • The theory of gravity is scalar

17. Certainly, the correct theory • Prediction of the existence of planets • Correctly describes the motion of the satellites • etc.

18. What is wrong? • Newton theory of gravity is not Lorentz-invariant. • Observations! The motion of the perihelion of Mercury is not described by this law.

19. Intermediate results • Correct theory must meet a certain set of fundamental properties (axioms). • General relativity is actually not the only possible theory of gravity (generalizing - field theory). • The question arises whether it is possible to determine the form of the theory (i.e. the form of the equations describing its basic laws), based only on general principles, that is, completely disregarding the observations.

20. Kinetic energy Is it possible:

21. Kinetic energy Is it possible: ?

22. Kinetic energy Is it possible:

23. Kinetic energy Is it possible:

24. An example: square latice

25. An example: square latice

26. Intermediate results • Correct theory must meet a certain set of fundamental properties (axioms). One of them - Lorentz invariance. • General relativity is actually not the only possible theory of gravity (generalizing - field theory). • In the limit of weak fields and low speeds we have to return to the old theory. • A big role to play invariants.

27. Important conclusions • General principles (symmetry, Lorentz invariance) can help limit the theory, but, in general, do not define it through. • When extending the theory necessary to introduce dimensional constants (mass M, velocity c), the values of which can only be determined from observations. • In the limiting case (in the example above - at non-relativistic velocities v << c) theory should be returned to well-known.One possible generalization - the transition from scalars (numbers) to tensors (tables).

28. An example – standard model

29. An example – standard model

30. An example – (non)standard model

31. Appearing of tensors • Quadratic forms kinetic energy metric • Linear dependence Hooke's law Ohm’s law

32. Ohm’s law • Homogeneous media • Hall current

33. Invariants of matrices • '‘Square'' of symmetric matrix • The sum of the diagonal elements - the so-called 'Trace' (in German 'Spur')

34. Problem Show that a square matrix is independent of the anglej

35. Metric

36. Metric • Cartesian • Cylindrical • Spherical

37. Metric • Arbitrary

38. Metric • En example – oblique grid Problem

39. And what with the invariants? For orthogonal coordinate (i.e. for the diagonal matrices)