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Full-Text Articles in Physics
K ->Pi Pi Phenomenology In The Presence Of Electromagnetism, V Cirigliano, Jf Donoghue, Eugene Golowich
K ->Pi Pi Phenomenology In The Presence Of Electromagnetism, V Cirigliano, Jf Donoghue, Eugene Golowich
Physics Department Faculty Publication Series
We describe the influence of electromagnetism on the phenomenology of $K \to \pi\pi$ decays. This is required because the present data were analyzed without inclusion of electromagnetic radiative corrections, and hence contain several ambiguities and uncertainties which we describe in detail. Our presentation includes a full description of the infrared effects needed for a new experimental analysis. It also describes the general treatment of final state interaction phases, needed because Watson's theorem is no longer valid in the presence of electromagnetism. The phase of the isospin-two amplitude ${\cal A}_2$ may be modified by $50 \to 100\%$. We provide a tentative …
Internal Diffusion-Limited Aggregation: Parallel Algorithms And Complexity, C Moore, J Machta
Internal Diffusion-Limited Aggregation: Parallel Algorithms And Complexity, C Moore, J Machta
Physics Department Faculty Publication Series
The computational complexity of internal diffusion-limited aggregation (DLA) is examined from both a theoretical and a practical point of view. We show that for two or more dimensions, the problem of predicting the cluster from a given set of paths is complete for the complexity class CC, the subset of P characterized by circuits composed of comparator gates. CC-completeness is believed to imply that, in the worst case, growing a cluster of size n requires polynomial time in n even on a parallel computer. A parallel relaxation algorithm is presented that uses the fact that clusters are nearly spherical to …
Comprehensive Study Of Fröhlich Polaron, A Mishchenko, N Prokof'ev, B Svistunov, A Sakamoto
Comprehensive Study Of Fröhlich Polaron, A Mishchenko, N Prokof'ev, B Svistunov, A Sakamoto
Physics Department Faculty Publication Series
A study of the Fröhlich polaron model is performed on the basis of diagrammatic quantum Monte Carlo technique which is enhanced by novel method of spectral analysis of the polaron Green function. We make available for the first time precise data for the effective mass, including the region of intermediate and strong couplings, and analyze the structure of the polaron cloud. A non-trivial structure of the spectral density is observed: at high enough couplings the spectral continuum features pronounced peaks that we attribute to unstable excited states of the polaron.
Supercurrent Stability In A Quasi-One-Dimensional Weakly Interacting Bose Gas, Y Kagan, Nikolai Prokof'ev, B Svistunov
Supercurrent Stability In A Quasi-One-Dimensional Weakly Interacting Bose Gas, Y Kagan, Nikolai Prokof'ev, B Svistunov
Physics Department Faculty Publication Series
We discuss the possibility of observing superfluid phenomena in a quasi-one-dimensional weakly interacting Bose gas at finite temperature. The weakness of interaction in combination with generic properties of one-dimensional liquids can result in a situation where the relaxation time of the supercurrent flow is much longer than the system lifetime, and the behavior of the system is indistinguishable from that of a genuine superfluid.
Validity Of The Hohenberg Theorem For A Generalized Bose-Einstein Condensation In Two Dimensions, W. J. Mullin, M. Holzmann, F. Lalö
Validity Of The Hohenberg Theorem For A Generalized Bose-Einstein Condensation In Two Dimensions, W. J. Mullin, M. Holzmann, F. Lalö
Physics Department Faculty Publication Series
Several authors have considered the possibility of a generalized Bose-Einstein condensation (BEC) in which a band of low states is occupied so that the total occupation number is macroscopic, even if the occupation number of each state is not extensive. The Hohenberg theorem (HT) states that there is no BEC into a single state in 2D; we consider its validity for the case of a generalized condensation and find that, under certain conditions, the HT does not forbid a BEC in 2D. We discuss whether this situation actually occurs in any theoretical model system.
The Loop-Gas Approach To Bose-Einstein Condensation For Trapped Particles, Wj Mullin
The Loop-Gas Approach To Bose-Einstein Condensation For Trapped Particles, Wj Mullin
Physics Department Faculty Publication Series
We examine Bose–Einstein condensation (BEC) for particles trapped in a harmonic potential by considering it as a transition in the length of permutation cycles that arise from wave-function symmetry. This “loop-gas” approach was originally developed by Feynman in his path-integral study of BEC for a homogeneous gas in a box. For the harmonic oscillator potential it is possible to treat the ideal gas exactly so that one can easily see how standard approximations become more accurate in the thermodynamic limit (TDL). One clearly sees that the condensate is made up of very long permutation loops whose length fluctuates ever more …
A Brief Introduction To Chiral Perturbation Theory, Br Holstein
A Brief Introduction To Chiral Perturbation Theory, Br Holstein
Physics Department Faculty Publication Series
A brief introduction to the subject of chiral perturbation theory (Xpt) is presented, including a discussion of effective field theory and applications of Xpt in the arena of purely mesonic interactions as well as in the πN sector.
Theory Of The Spin Bath, Nikolai Prokof'ev, P.C.E Stamp
Theory Of The Spin Bath, Nikolai Prokof'ev, P.C.E Stamp
Physics Department Faculty Publication Series
The quantum dynamics of mesoscopic or macroscopic systems is always complicated by their coupling to many `environmental' modes. At low T these environmental effects are dominated by localized modes, such as nuclear and paramagnetic spins, and defects (which also dominate the entropy and specific heat). This environment, at low energies, maps onto a `spin bath' model. This contrasts with `oscillator bath' models (originated by Feynman and Vernon) which describe delocalized environmental modes such as electrons, phonons, photons, magnons, etc. The couplings to N spin bath modes are independent of N (rather than the ~O(1/(N )1/2 ) dependence typical of oscillator …
Instability In A Two-Dimensional Dilute Interacting Bose System, W. J. Mullin, M. Holzmann, F. Laloë
Instability In A Two-Dimensional Dilute Interacting Bose System, W. J. Mullin, M. Holzmann, F. Laloë
Physics Department Faculty Publication Series
The formalism of Ursell operators provides a self-consistent integral equation for the one-particle reduced operator. In three dimensions this technique yields values of the shift in the Bose-Einstein condensation (BEC) transition temperature, as a function of the scattering length, that are in good agreement with those of Green’s function and quantum Monte Carlo methods. We have applied the same equations to a uniform two-dimensional system and find that, as we alter the chemical potential, an instability develops so that the self-consistent equations no longer have a solution. This instability, which seems to indicate that interactions restore a transition, occurs at …