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- """
- Naturalunit system.
- The natural system comes from "setting c = 1, hbar = 1". From the computer
- point of view it means that we use velocity and action instead of length and
- time. Moreover instead of mass we use energy.
- """
- from sympy.physics.units import DimensionSystem
- from sympy.physics.units.definitions import c, eV, hbar
- from sympy.physics.units.definitions.dimension_definitions import (
- action, energy, force, frequency, length, mass, momentum,
- power, time, velocity)
- from sympy.physics.units.prefixes import PREFIXES, prefix_unit
- from sympy.physics.units.unitsystem import UnitSystem
- # dimension system
- _natural_dim = DimensionSystem(
- base_dims=(action, energy, velocity),
- derived_dims=(length, mass, time, momentum, force, power, frequency)
- )
- units = prefix_unit(eV, PREFIXES)
- # unit system
- natural = UnitSystem(base_units=(hbar, eV, c), units=units, name="Natural system")
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