The microcanonical thermodynamics of finite systems: The microscopic origin of condensation and phase separations; and the conditions for heat flow from lower to higher temperatures

Microcanonical thermodynamics allows the application of statistical mechanics both to finite and even small systems and also to the largest, self-gravitating ones. However, one must reconsider the fundamental principles of statistical mechanics especially its key quantity, entropy. Whereas in conventional thermostatistics, the homogeneity and extensivity of the system and the concavity of its entropy are central conditions, these fail for the systems considered here. For example, at phase separation, the entropy, S(E), is necessarily convex to make exp[S(E)-E/T] bimodal in E. Particularly, as inhomogeneities and surface effects cannot be scaled away, one must be careful with the standard arguments of splitting a system into two subsystems, or bringing two systems into thermal contact with energy or particle exchange. Not only the volume part of the entropy must be considered. As will be shown here, when removing constraints in regions of a negative heat capacity, the system may even relax under a flow of heat (energy) against a temperature slope. Thus the Clausius formulation of the second law: ``Heat always flows from hot to cold'', can be violated. Temperature is not a necessary or fundamental control parameter of thermostatistics. However, the second law is still satisfied and the total Boltzmann entropy increases. In the final sections of this paper, the general microscopic mechanism leading to condensation and to the convexity of the microcanonical entropy at phase separation is sketched. Also the microscopic conditions for the existence (or non-existence) of a critical end-point of the phase-separation are discussed. This is explained for the liquid-gas and the solid-liquid transition.Comment: 23 pages, 2 figures, Accepted for publication in the Journal of Chemical Physic

Unzipping of DNA with correlated base-sequence

We consider force-induced unzipping transition for a heterogeneous DNA model with a correlated base-sequence. Both finite-range and long-range correlated situations are considered. It is shown that finite-range correlations increase stability of DNA with respect to the external unzipping force. Due to long-range correlations the number of unzipped base-pairs displays two widely different scenarios depending on the details of the base-sequence: either there is no unzipping phase-transition at all, or the transition is realized via a sequence of jumps with magnitude comparable to the size of the system. Both scenarios are different from the behavior of the average number of unzipped base-pairs (non-self-averaging). The results can be relevant for explaining the biological purpose of correlated structures in DNA.Comment: 22 pages, revtex4, 14 eps figures; reprinted in the June 15, 2004 issue of Virtual Journal of Biological Physics Researc

The Finite Temperature SU(2) Savvidy Model with a Non-trivial Polyakov Loop

We calculate the complete one-loop effective potential for SU(2) gauge bosons at temperature T as a function of two variables: phi, the angle associated with a non-trivial Polyakov loop, and H, a constant background chromomagnetic field. Using techniques broadly applicable to finite temperature field theories, we develop both low and high temperature expansions. At low temperatures, the real part of the effective potential V_R indicates a rich phase structure, with a discontinuous alternation between confined (phi=pi) and deconfined phases (phi=0). The background field H moves slowly upward from its zero-temperature value as T increases, in such a way that sqrt(gH)/(pi T) is approximately an integer. Beyond a certain temperature on the order of sqrt(gH), the deconfined phase is always preferred. At high temperatures, where asymptotic freedom applies, the deconfined phase phi=0 is always preferred, and sqrt(gH) is of order g^2(T)T. The imaginary part of the effective potential is non-zero at the global minimum of V_R for all temperatures. A non-perturbative magnetic screening mass of the form M_m = cg^2(T)T with a sufficiently large coefficient c removes this instability at high temperature, leading to a stable high-temperature phase with phi=0 and H=0, characteristic of a weakly-interacting gas of gauge particles. The value of M_m obtained is comparable with lattice estimates.Comment: 28 pages, 5 eps figures; RevTeX 3 with graphic

On the Spontaneous CP Breaking at Finite Temperature in a Nonminimal Supersymmetric Standard Model

We study the spontaneous CP breaking at finite temperature in the Higgs sector in the Minimal Supersymmetric Standard Model with a gauge singlet. We consider the contribution of the standard model particles and that of stops, charginos, neutralinos, charged and neutral Higgs boson to the one-loop effective potential. Plasma effects for all bosons are also included. Assuming CP conservation at zero temperature, so that experimental constraints coming from, {\it e.g.}, the electric dipole moment of the neutron are avoided, and the electroweak phase transition to be of the first order and proceeding via bubble nucleation, we show that spontaneous CP breaking cannot occur inside the bubble mainly due to large effects coming from the Higgs sector. However, spontaneous CP breaking can be present in the region of interest for the generation of the baryon asymmetry, namely inside the bubble wall. The important presence of very tiny explicit CP violating phases is also commented.Comment: 28 pages, 4 figures available upon request, DFPD 94/TH/38 and SISSA 94/81-A preprint

Yang-Mills Correlation Functions from Integrable Spin Chains

The relation between the dilatation operator of N=4 Yang-Mills theory and integrable spin chains makes it possible to compute the one-loop anomalous dimensions of all operators in the theory. In this paper we show how to apply the technology of integrable spin chains to the calculation of Yang-Mills correlation functions by expressing them in terms of matrix elements of spin operators on the corresponding spin chain. We illustrate this method with several examples in the SU(2) sector described by the XXX_1/2 chain.Comment: 27 pages, 3 figures, harvma

From Coherent Modes to Turbulence and Granulation of Trapped Gases

The process of exciting the gas of trapped bosons from an equilibrium initial state to strongly nonequilibrium states is described as a procedure of symmetry restoration caused by external perturbations. Initially, the trapped gas is cooled down to such low temperatures, when practically all atoms are in Bose-Einstein condensed state, which implies the broken global gauge symmetry. Excitations are realized either by imposing external alternating fields, modulating the trapping potential and shaking the cloud of trapped atoms, or it can be done by varying atomic interactions by means of Feshbach resonance techniques. Gradually increasing the amount of energy pumped into the system, which is realized either by strengthening the modulation amplitude or by increasing the excitation time, produces a series of nonequilibrium states, with the growing fraction of atoms for which the gauge symmetry is restored. In this way, the initial equilibrium system, with the broken gauge symmetry and all atoms condensed, can be excited to the state, where all atoms are in the normal state, with completely restored gauge symmetry. In this process, the system, starting from the regular superfluid state, passes through the states of vortex superfluid, turbulent superfluid, heterophase granular fluid, to the state of normal chaotic fluid in turbulent regime. Both theoretical and experimental studies are presented.Comment: Latex file, 25 pages, 4 figure

The modulation effect for supersymmetric dark matter detection with asymmetric velocity dispersion

The detection of the theoretically expected dark matter is central to particle physics cosmology. Current fashionable supersymmetric models provide a natural dark matter candidate which is the lightest supersymmetric particle (LSP). Such models combined with fairly well understood physics like the quark substructure of the nucleon and the nuclear form factor and the spin response function of the nucleus, permit the evaluation of the event rate for LSP-nucleus elastic scattering. The thus obtained event rates are, however, very low or even undetectable. So it is imperative to exploit the modulation effect, i.e. the dependence of the event rate on the earth's annual motion. In this review we study such a modulation effect in directional and undirectional experiments. We calculate both the differential and the total rates using symmetric as well as asymmetric velocity distributions. We find that in the symmetric case the modulation amplitude is small, less than 0.07. There exist, however, regions of the phase space and experimental conditions such that the effect can become larger. The inclusion of asymmetry, with a realistic enhanced velocity dispersion in the galactocentric direction, yields the bonus of an enhanced modulation effect, with an amplitude which for certain parameters can become as large as 0.46.Comment: 35 LATEX pages, 7 Tables, 8 PostScript Figures include

End-of-Life Care for Patients with Metastatic Renal Cell Carcinoma in the Era of Oral Anticancer Therapy

PURPOSE:New therapies including oral anticancer agents (OAAs) have improved outcomes for patients with metastatic renal cell carcinoma (mRCC). However, little is known about the quality of end-of-life (EOL) care and systemic therapy use at EOL in patients receiving OAAs or with mRCC.METHODS:We retrospectively analyzed EOL care for decedents with mRCC in two parallel cohorts: (1) patients (RCC diagnosed 2004-2015) from the University of North Carolina's Cancer Information and Population Health Resource (CIPHR) and (2) patients (diagnosed 2007-2015) from SEER-Medicare. We assessed hospice use in the last 30 days of life and existing measures of poor-quality EOL care: systemic therapy, hospital admission, intensive care unit admission, and > 1 ED visit in the last 30 days of life; hospice initiation in the last 3 days of life; and in-hospital death. Associations between OAA use, patient and provider characteristics, and EOL care were examined using multivariable logistic regression.RESULTS:We identified 410 decedents in the CIPHR cohort (53.4% received OAA) and 1,508 in SEER-Medicare (43.5% received OAA). Prior OAA use was associated with increased systemic therapy in the last 30 days of life in both cohorts (CIPHR: 26.5% v 11.0%; P <.001; SEER-Medicare: 23.4% v 11.7%; P <.001), increased in-hospital death in CIPHR, and increased hospice in the last 30 days in SEER-Medicare. Older patients were less likely to receive systemic therapy or be admitted in the last 30 days or die in hospital.CONCLUSION:Patients with mRCC who received OAAs and younger patients experienced more aggressive EOL care, suggesting opportunities to optimize high-quality EOL care in these groups

Severe neurological outcomes after very early bilateral nephrectomies in patients with autosomal recessive polycystic kidney disease (ARPKD)

To test the association between bilateral nephrectomies in patients with autosomal recessive polycystic kidney disease (ARPKD) and long-term clinical outcome and to identify risk factors for severe outcomes, a dataset comprising 504 patients from the international registry study ARegPKD was analyzed for characteristics and complications of patients with very early (� 3 months; VEBNE) and early (4�15 months; EBNE) bilateral nephrectomies. Patients with very early dialysis (VED, onset � 3 months) without bilateral nephrectomies and patients with total kidney volumes (TKV) comparable to VEBNE infants served as additional control groups. We identified 19 children with VEBNE, 9 with EBNE, 12 with VED and 11 in the TKV control group. VEBNE patients suffered more frequently from severe neurological complications in comparison to all control patients. Very early bilateral nephrectomies and documentation of severe hypotensive episodes were independent risk factors for severe neurological complications. Bilateral nephrectomies within the first 3 months of life are associated with a risk of severe neurological complications later in life. Our data support a very cautious indication of very early bilateral nephrectomies in ARPKD, especially in patients with residual kidney function, and emphasize the importance of avoiding severe hypotensive episodes in this at-risk cohort. © 2020, The Author(s)