  Motivated by how transaction amount constrain trading volume and price
volatility in stock market, we, in this paper, study the relation between
volume and price if amount of transaction is given. We find that accumulative
trading volume gradually emerges a kurtosis near the price mean value over a
trading price range when it takes a longer trading time, regardless of actual
price fluctuation path, time series, or total transaction volume in the time
interval. To explain the volume-price behavior, we, in terms of physics,
propose a transaction energy hypothesis, derive a time-independent transaction
volume-price probability wave equation, and get two sets of analytical volume
distribution eigenfunctions over a trading price range. By empiric test, we
show the existence of coherence in stock market and demonstrate the model
validation at this early stage. The volume-price behaves like a probability
wave.
