Q: Which tense should be used in the abstract of a paper?

While writing your abstract, you can use several tenses depending on the subject of your sentence. You can keep in mind the general rules regarding tense usage while you write your Abstract:

• Use present tense while stating general facts
• Use past tense when writing about prior research
• Use past tense when stating results or observations
• Use present tense when stating the conclusion or interpretations
• Use present tense when referring to your study/paper

You can refer these articles to better understand how you should use tense in scientific writing:

• INFOGRAPHIC: The secret to using tenses in scientific writing
• Using past and present tenses in research writing
• Getting the tenses right: Materials and methods section
• Is it acceptable to use first person pronouns in scientific writing?