Final answer:
The assumption of a single global market leads to a global market. If the U.S. economy grows rapidly, U.S. financial markets would likely see increased demand for financial assets, potential asset price increases, and could affect global borrowing costs. The definition of markets may expand, presenting challenges for antitrust authorities internationally.
Step-by-step explanation:
The assumption that a single global market exists would lead to a global market. In such a global market, there would be an increased integration of different national markets into one large marketplace, where goods, services, and capital flow freely across borders.
If the U.S. economy began to grow more rapidly than other countries, the likely impact on U.S. financial markets as part of the global economy would be significant. Firstly, the demand for U.S. financial assets might increase as investors seek opportunities in a rapidly growing economy, which could lead to a rise in asset prices and potentially strengthen the U.S. dollar. Additionally, U.S. interest rates could rise if the central bank decides to address concerns about inflation due to economic growth. A more robust U.S. economy could draw in foreign investment, but it may also lead to higher costs of borrowing for other countries as global capital gravitates towards the U.S.
Further, the definition of markets may broaden due to greater global competition, which doesn't imply that antitrust authorities have lesser responsibilities. In fact, there might be an increased concern over monopolies extending their reach internationally, challenging national authorities to regulate these entities effectively. This dynamic interplay shapes the landscape of global financial markets.