RX feedback loop

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reactive.Concurrency;
using System.Reactive.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
	class Program
	{
		private static void Main(string[] args)
		{
			const double dt = 0.01; // seconds
			const double k = 1;
			const double m = 1;
			const double x0 = 100;

			var timer = Observable.Timer(DateTimeOffset.Now, TimeSpan.FromSeconds(dt));

			// Hooke's law: 
			// f = -k * x
			// a = f/m
			// v = integral(a)
			// x = x0 + integral(v)

			IObservable<double> sigX = null;
			sigX = Observable.Defer(
				() =>
				{
					var sigF = sigX.Select(x => -x * k);
					var sigA = sigF.Select(f => f / m);
					var sigV = sigA.Scan(0.0, (v, a) => v + a * dt);
					return sigV.Scan(x0, (x, v) => x + v * dt);
				})
				.Publish(x0)
				.RefCount()
				.Sample(timer);

			sigX.Subscribe(x => Console.Write("\r{0,10:F2}",x));

			Console.ReadLine();
		}
	}
}