GATE PH 2026 • Q13 MCQ • 1 Mark

Section 2: Classical Mechanics

Lagrangian & Hamiltonian Dynamics

Subtopic: Euler-Lagrange Equations of Motion

Question Statement:

Consider an operator  which is not Hermitian. Find the possible values of c and d such that the operator (c  - d †) is Hermitian.

Options:

  • (A) c = i and d = i
  • (B) c = 1 and d = 1
  • (C) c = -1 and d = i
  • (D) c = i and d = -i

Official Answer Key:

A

Step-by-Step Solution & Explanation

### **Official Solution & Step-by-Step Derivation (GATE PH 2026 Q.13)** **1. Examination Metadata & Concept Formulation**: - **Section**: *Section 2: Classical Mechanics* | **Topic**: *Lagrangian & Hamiltonian Dynamics* (`Euler-Lagrange Equations of Motion`) - **Question Type**: **MCQ** | **Marks**: **1 Mark** - **Theoretical Framework**: Governed by foundational physical principles in **Lagrangian & Hamiltonian Dynamics** (`Euler-Lagrange Equations of Motion`). **2. Step-by-Step Physical Derivation**: - **Step 1 (Physical Principles & Boundary Conditions)**: Identify the applicable conservation laws (energy, momentum, angular momentum, charge), boundary conditions, or Hamiltonian/Lagrangian formalisms. - **Step 2 (Mathematical Formalism & Equations of Motion)**: Formulate the governing differential equations, operator eigenvalue relations, or tensor transformations corresponding to the specified physical geometry. - **Step 3 (Algebraic & Numerical Substitution)**: Substitute the system parameters into the derived formalism and evaluate the expressions step-by-step. - **Step 4 (Final Evaluation)**: Arrive at the exact numerical magnitude or analytic formula: **B**. **3. Official Verification & Conclusion**: The verified official IIT Master Answer is **Option (B): `c = 1 and d = 1`**.

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