TY - JOUR AB - We study the BCS gap equation for a Fermi gas with unequal population of spin-up and spin-down states. For cosh (δ μ/T) ≤ 2, with T the temperature and δμ the chemical potential difference, the question of existence of non-trivial solutions can be reduced to spectral properties of a linear operator, similar to the unpolarized case studied previously in [Frank, R. L., Hainzl, C., Naboko, S., and Seiringer, R., J., Geom. Anal.17, 559-567 (2007)10.1007/BF02937429; Hainzl, C., Hamza, E., Seiringer, R., and Solovej, J. P., Commun., Math. Phys.281, 349-367 (2008)10.1007/s00220-008-0489-2; and Hainzl, C. and Seiringer, R., Phys. Rev. B77, 184517-110 435 (2008)]10.1103/PhysRevB.77.184517. For cosh (δ μ/T) > 2 the phase diagram is more complicated, however. We derive upper and lower bounds for the critical temperature, and study their behavior in the small coupling limit. AU - Freiji, Abraham AU - Hainzl, Christian AU - Robert Seiringer ID - 2394 IS - 1 JF - Journal of Mathematical Physics TI - The gap equation for spin-polarized fermions VL - 53 ER - TY - JOUR AB - We give the first rigorous derivation of the celebrated Ginzburg-Landau (GL) theory, starting from the microscopic Bardeen-Cooper-Schrieffer (BCS) model. Close to the critical temperature, GL arises as an effective theory on the macroscopic scale. The relevant scaling limit is semiclassical in nature, and semiclassical analysis, with minimal regularity assumptions, plays an important part in our proof. AU - Frank, Rupert L AU - Hainzl, Christian AU - Robert Seiringer AU - Solovej, Jan P ID - 2395 IS - 3 JF - Journal of the American Mathematical Society TI - Microscopic derivation of Ginzburg-Landau theory VL - 25 ER - TY - JOUR AB - A positive temperature analogue of the scattering length of a potential V can be defined via integrating the difference of the heat kernels of -Δ and, with Δ the Laplacian. An upper bound on this quantity is a crucial input in the derivation of a bound on the critical temperature of a dilute Bose gas (Seiringer and Ueltschi in Phys Rev B 80:014502, 2009). In (Seiringer and Ueltschi in Phys Rev B 80:014502, 2009), a bound was given in the case of finite range potentials and sufficiently low temperature. In this paper, we improve the bound and extend it to potentials of infinite range. AU - Landon, Benjamin AU - Robert Seiringer ID - 2396 IS - 3 JF - Letters in Mathematical Physics TI - The scattering length at positive temperature VL - 100 ER - TY - GEN AB - We extend the mathematical theory of quantum hypothesis testing to the general W*-algebraic setting and explore its relation with recent developments in non-equilibrium quantum statistical mechanics. In particular, we relate the large deviation principle for the full counting statistics of entropy flow to quantum hypothesis testing of the arrow of time. AU - Jakšić, Vojkan AU - Ogata, Yoshiko AU - Pillet, Claude A AU - Robert Seiringer ID - 2398 IS - 6 T2 - Reviews in Mathematical Physics TI - Quantum hypothesis testing and non-equilibrium statistical mechanics VL - 24 ER - TY - JOUR AB - We consider the low-density limit of a Fermi gas in the BCS approximation. We show that if the interaction potential allows for a two-particle bound state, the system at zero temperature is well approximated by the Gross-Pitaevskii functional, describing a Bose-Einstein condensate of fermion pairs. AU - Hainzl, Christian AU - Robert Seiringer ID - 2397 IS - 2 JF - Letters in Mathematical Physics TI - Low density limit of BCS theory and Bose-Einstein condensation of Fermion pairs VL - 100 ER -