U.S. Stocks Mixed: Dow Falls on UnitedHealth Probe, Nasdaq Rises

Key Metrics:

* S&P 500 (^GSPC): Flat
* Nasdaq Composite (^IXIC): +0.2%
* Dow Jones Industrial Average (^DJI): -0.5%

Market Movers:

* UnitedHealth (UNH): Shares tumbled 11% amid a Department of Justice probe into Medicare billing practices.
* Celsius Holdings (CELH): Soared 30% after announcing the acquisition of Alani Nutrition for $1.8 billion.
* Walmart's warning on tariff uncertainty contributed to Thursday's market downturn.

Earnings & Economic Data:

* Earnings: No major releases on Friday.
* Economic data: Existing home sales (January) and consumer sentiment (University of Michigan).

Tariffs Impact:

* President Trump's tariffs continue to weigh on retailers and consumers.
* Walmart may pass price hikes on to customers if tariffs impact its bottom line.

Other Highlights:

* Nvidia's upcoming earnings may have a diminished impact on the market compared to previous years.
* Homebuilders face challenges due to high interest rates and tariff fears.
* Gold remains in an upward trend, driven by ETF inflows.