In a significant development that could redefine corporate competition and regulatory oversight, the Department of Justice (DOJ) is reportedly preparing to launch an antitrust probe into Nvidia (NVDA), a global powerhouse in the Artificial Intelligence field. This announcement has sent shockwaves through the investor community, causing fluctuations in Nvidia's stock prices. Meanwhile, Apple, another leading player in the tech industry has also been nudged off its coveted second spot by Nvidia after a massive leap in Nvidia's stock prices to $3.

The actions by the DOJ seem to echo a central theme in US regulatory activities targeted at curbing monopolization and promoting ethical business practices in the tech industry. However, with the revelation of this pending investigation, Apple’s position as a key player in the tech marketplace has been further emphasized.

It is significant to note that this is not the first time such powerhouses have faced scrutiny from the DOJ. Apple in the past has had its fair share of brushes with antitrust laws and regulations. This recent development serves as a stark reminder of regulatory oversight in the United States' highly competitive tech industry.

However, it is worth noting that this potential probe into Nvidia's business practices could indirectly impact Apple, considering the intense competition within the technology sector. How the market shares of these companies will be affected by the reported DOJ probe into Nvidia, and the subsequent response from the investing community, remains an intriguing story to follow.

This development underscores the ruthless competition and the crucial role of regulatory bodies in enforcing ethical business practices. The scenario also reiterates the stiff competition between Nvidia and Apple, two giants in the tech industry, setting the stage for a captivating rivalry in the tech market.

The looming investigation into Nvidia by the Department of Justice, along with the fluctuations in Apple and Nvidia's rankings, symbolizes the fluid dynamics of the technology market. It will also determine how these tech titans operate amidst increasing scrutiny and tight regulatory controls.

In conclusion, the tech industry is continuously evolving, with corporate giants like Nvidia and Apple continually pushing the boundaries of technology. However, it becomes crucial that these evolving landscapes do not compromise ethical business practices or stifle competition, hence the decisive role of regulatory bodies like the Department of Justice in maintaining balance and fairness in the industry. The end goal is a competitive, ethical business environment that fosters healthy competition and drives innovation.