Re: MacBook Pro Keeps Shutting Down - Hardware Or Mavericks Causing It?
Is it possible you're accidentally brushing the power button when this happens? Mavericks changed the way sleep mode activates, so it goes to sleep right away after that button's pressed rather than asking what to do (sleep, shut off or restart).
Assuming that's _not_ the case, please try to describe the problem in a bit more detail. Is it powering down all together or just entering sleep mode? Does it seem tied to any particular activity? Do you hear any unusual fan noise? Is it more prone to happen when running a particular application?
Also, try to clear NVRAM (by holding down the command, option, P and R keys simultaneously on boot, until you hear the boot chime three times, then let go) and reset the System Management Controller (SMC) (by shutting down your Mac, unplugging the power supply and holding down the control, option and power buttons simultaneously).
The SMC, in particular, manages specific aspects of how the Mac's power management works.
Assuming none of that fixes things, I might recommend a trip to your local Genius Bar or Apple Authorized Service Provider (AASP) to have it looked at.