The success of Apple Inc.’s iPad has prompted other tech companies to plunge into the market for tablet computers, with start-ups and major PC makers racing to introduce their own competing devices before the end of the year, the Los Angeles Times reports. Verizon Wireless Inc. confirmed Tuesday that it has a tablet in the works. Speculation is swirling around the intentions of Hewlett-Packard Co., the world’s biggest PC maker and the company that some believe has the best shot at catching up with Apple’s early iPad lead. Meanwhile, everyone from upstart Fusion Garage to established names such as Dell Inc. is jumping into the pool. Experts say the iPad’s early sales figures — Apple reported it sold 1 million units in four weeks — are proof there’s a strong market for such products. But it’s unclear whether other manufacturers can duplicate the iPad’s appeal, or whether Apple will dominate the market in the same way its iPod is king of the portable music player market.