AMPS doesn't have any requirement to predefine topics for publish and subscribe. You can publish to whatever topic name your application needs to, and subscribe to any topic your application needs to subscribe to (including regular expression topics).
Most AMPS configuration files, including the sample configuration, include topic definitions. These definitions give AMPS the information it needs to keep the State of the World (SOW) for those topics. The definitions aren't required for simply publishing and subscribing to topics, but are required to keep a SOW (or use any of the features that depend on the SOW).