The general solutions for the harmonic oscillator differential equation fall into four general categories: 1) Undamped: [math]x(t) = Ae^{i\omega t}[/math] This is a free-running sinusoidal oscillation that doesn't change over time.
Key Facts. 1  Itâs normal to have mild cramps during your period. 2  Menstrual cramps often start 1-2 days after your period begins. 3  If your cramps donât get better with over-the-counter medicine, you should see your health care provider.
Cramps (pain in the lower belly area and/or lower back) can start 1-2 days before your period comes and can last 2-4 days. Secondary dysmenorrhea is when cramps and, for some, lower back pain are a result of a medical problem such as endometriosis or pelvic inflammatory disease.ramps (pain in the lower belly area and/or lower back) can start 1-2 days before your period comes and can last 2-4 days. Secondary dysmenorrhea is when cramps and, for some, lower back pain are a result of a medical problem such as endometriosis or pelvic inflammatory disease.