If string theory were definitively falsified, the impact on brane cosmology models and Planck epoch research would be profound and multifaceted. Here's a structured analysis of the implications:

1. Theoretical Foundations Collapse

   - Brane methodology would lose its fundamental basis, as it's intrinsically derived from string theory's framework of extra dimensions.

   - Planck epoch models relying on string-theoretic concepts (e.g., vibrating strings as fundamental entities, brane collisions as Big Bang alternatives) would become untenable.

 2. Specific Model Impacts

   | **Randall-Sundrum (RS) | Invalidated - extra dimensions and warped geometry lose theoretical justification |

   | Ekpyrotic/Cyclic Universes | Rendered obsolete (rely on brane collisions) |

   | String Gas Cosmology Abandoned (depends on string thermodynamics) |

   | Holographic Principle  Severely weakened (AdS/CFT correspondence is string-derived) |

   | Brane Inflation  | All specific implementations (e.g., D-brane, KKLMMT) invalidated |

 3. Shift in Research Focus

   - Alternative quantum gravity theories would dominate:

     - Loop Quantum Gravity (LQG): Spin networks for Planck-scale spacetime

     - Causal Sets: Discrete spacetime foundations

     - Asymptotic Safety: Quantum field theory approaches

   - Modified gravity theories (e.g., $f(R)$ gravity, teleparallelism) would gain prominence for dark energy/dark matter explanations.

4. Observational Consequences

   - Priorities would shift** toward tests of alternative theories:

     - LQG's predictions for cosmic bounce instead of singularity

     - CMB signatures from non-string quantum fluctuations

     - Gravitational wave patterns from non-string early universe phase transitions

   - Current anomalies (e.g., CMB hemispherical asymmetry) would be reinterpreted without string-theoretic explanations.

5. Conceptual Paradigm Shifts

   - Extra dimensions Would shift from physical reality to mathematical curiosity

   - Quantum gravity timeline Planck epoch studies would reboot using:

   - Theory evaluation criteria. Greater emphasis on experimental falsifiability over mathematical elegance.  

6. Unresolved Challenges Amplified

   - The cosmological constant problem would lose string landscape as a potential solution

   -  Initial singularity resolution would require entirely new mechanisms

   - UV completion of inflation would need non-string approaches

7.  Silver Linings

   - Increased funding/attention for:

     1. Quantum gravity phenomenology

     2. Laboratory tests of quantum spacetime

     3. High-precision cosmology experiments

   - Accelerated development of:

     - Quantum computing simulations of spacetime

     - Gravitational wave detectors (LISA, Einstein Telescope)

     - CMB Stage-5 experiments

Synthesis

While brane-based Planck epoch models would collapse, cosmology would undergo a creative transformation. The field would likely experience short-term disruption but long-term renewal through:

- Radical theory diversification

- Stronger observation-theory coupling

- Emergence of new paradigms from alternative quantum gravity frameworks

The falsification would ultimately refocus cosmology on empirically testable quantum gravity signatures rather than mathematical unification, potentially accelerating the resolution of foundational mysteries.