Critical phenomena Research Papers - Academia.edu (original) (raw)

2025, Journal of Statistical Physics

The critical properties of the Potts model with q = 3 and 8 states in one-dimension on directed small-world networks are investigated. This disordered system is simulated by updating it with the Monte Carlo heat bath algorithm. The Potts model on these directed small-world networks presents in fact a second-order phase transition with a new set of critical exponents for q = 3 considering a rewiring probability p = 0.1. For q = 8 the system exhibits only a first-order phase transition independent of p.

2025, Physica B-Condensed Matter

Dynamic magnetic susceptibilities of permalloy antidot array film were studied using threedimensional (3D) object oriented micromagnetic framework (OOMMF) code with two dimensional periodic boundary condition (2DPBC) extension. Two major resonance peaks associated with different regions were found in the investigated systems. Both resonance frequencies decrease with increasing inter-hole distance. The frequency corresponding to lower resonance peak increases with increasing film thickness for to 20 nm, and then the resonance frequency varies weakly with the thickness. High frequency resonance peak increases with decreasing inner radius, and disappears when the inner radius is below 10 nm. Low resonance frequency varies from 1.72 to 6.4 GHz when inner radius changes from 5 to 40 nm.

2025, Physical review. E

In this article, we present an approach for the thermodynamics of phase oscillators induced by an internal multiplicative noise. We analytically derive the free energy, entropy, internal energy, and specific heat. In this framework, the formulation of the first law of thermodynamics requires the definition of a synchronization field acting on the phase oscillators. By introducing the synchronization field, we have consistently obtained the susceptibility and analyzed its behavior. This allows us to characterize distinct phases in the system, which we have denoted as synchronized and parasynchronized phases, in analogy with magnetism. The system also shows a rich complex behavior, exhibiting ideal gas characteristics for low temperatures and susceptibility anomalies that are similar to those present in complex fluids such as water.

2025, Physics Letters B

We find the precise relationship between the loop gas method and the matrix quantum mechanics approach to two-dimensional string theory. The two systems are distinguished by different target spaces (Z Z and IR, respectively) as far as observables are concerned. We argue that target space loop correlators should coincide in the two models and demonstrate this for a number of examples. As a consequence some interesting generic observations about the structure of two-dimensional string theory may be made: Restricting to a discrete target space leads to factorization of amplitudes and thus to very simple sewing rules. It is also demonstrated that the restriction to the discrete target space still allows to calculate the correlation functions of tachyon operators in the unrestricted theory.

2025, Physics Letters A

In our recent Letter [Phys. Lett. A 222 ( 1996) 3751, it is shown (using data taken from the CfA2 catalogue) that there exists a phase transition from fractality to homogeneity in the large-scale universe. In the present Letter it is shown that this phenomenon is a consequence of a generalized scaling (some kind of self-similarity of random systems). It is also shown, by analysis of data obtained by different authors, that the generalized scaling and the multifractal phase transition to homogeneity occur in diffusive and growth processes as well as in percolation. Finally, recent data from the Perseus-Pisces survey are used to demonstrate universality of this phenomenon for the luminosity-space galaxy distributions of the large-scale universe.

2025, The European Physical Journal B

Multifractal critical phenomena with infinite-temperature critical point and with complex coexistence of the infinite and finite temperature critical points are considered and it is shown that strange attractors generated by cascades of period-doubling bifurcations (Feigenbaum scenario) as well as fields of velocity differences in fluid turbulence belong to the former subclass of the multifractal critical phenomena, while the real traffic processes and real currency exchange processes belong to the last (complex) subclass of the multifractal critical phenomena. Data obtained by different authors are used for this purpose.

2025, Physical review

When differential real-space renormalization-group theory was proposed by Hilhorst, Schick, and van Leeuwen, they suggested that their approach could only be applied to lattice models for which a star-triangle transformation exists. However, differential renormalization-group equations for the square Ising model have recently been proposed whose derivation does not involve the star-triangle transformation. We show that the latter equations are not exact renormalization-group equations by an analysis that reveals some essential limitations of the present formulation of differential real-space renormalization. We investigate the structure of the renormalization-group flow equations obtained in this method and uncover a strong property of these equations that simplifies the calculations in actual applications of the theory. However, the status and implications of this property, which embodies the crux of the theory, are not yet fully understood.

2025, Physical Review Letters

Crystallization waves exist at the 4He solid-liquid interface at low temperatures that are analogous to capillary waves at a liquid-air interface. Standing capillary waves can also be excited parametrically leading to the so-called Faraday instability. We analyze here the analog of this instability for crystallization waves. The threshold for the instability is independent of the surface stiffness at low temperatures, and therefore also independent of the crystalline anisotropy. The symmetry of surface patterns above the instability threshold, on the other hand, is argued to be sensitive to crystalline anisotropy.

2025, Journal of Physics: Conference Series

Periodic modulation of the gravity acceleration makes a flat surface of a fluid unstable and standing waves are parametrically excited on the surface. This phenomenon is called Faraday instability. Since a crystal-superfluid interface of 4 He at low temperatures is very mobile and behaves like a fluid surface, Saarloos and Weeks predicted that Faraday instability of the crystallization waves exists in 4 He and that the threshold excitation for the instability depends on the crystal growth coefficient. We successfully observed the Faraday instability of the crystal-liquid interface at 160 mK. Faraday waves were parametrically generated at one half of the driving frequency 90 Hz. Amplitude of the Faraday wave becomes smaller at higher temperature due to decrease of the crystal growth coefficient and disappears above 200 mK.

2025, Physical review

The Martin-Siggia-Rose field theories associated with the critical dynamics of mode-coupling systems, are renormalized in a way which decouples statics from dynamics, through the minimal- renormalization procedure. This simplifies considerably the computations which are thus carried out to two-loop order for exponent and Wilson functions. We obtain all dynamic transients for helium, O(n) symmetric antiferromagnets, and liquid-gas systems. We also discuss the relevance for helium of a fixed point where dynamic scaling is weakly violated. ' 2 By, (t) Taking the average over 0, with the probability law 6'(e) yields the functional which generates the correlation functions z (() Jl ae, (=t-) tp(e) z"((} z"(0) If orle retIiembers that, from (1.5), Z"(0) = I, the in- tegration over 0; is readily done to yield t Z ((} -= J ay, (t) &y, (t) exp 8 (y, y}+ dt (;(t)y;(t) By, (t) --I 5K, (y) = Jt ay, (t)ay, (t) exp J dt (, (t)y, (t)+ty, ' +K, (y) y, (t)(ro)"y-, (t)

2025, Journal of physics

The semi-infinite generalised Blume-Emery-Griffiths model of 3He-4He mixtures with a vector order parameter is analysed by means of Migdal-Kadanoff recursion relations. Superfluid film formation near the wall is put into evidence as a Kosterlitz-Thouless type transition. At higher 'He concentrations one observes the separation of a 4He rich normal film near the wall. Superfluid film formation near the wall in 3He-4He mixtures, first observed many years ago by (see also Gearhart and Zimmermann 1974, Romagnan er a1 1978, Ruppeiner er a1 1980) has been recently considered within the general theory of surface and special transitions (see e.g. Binder 1984) by . The physical mechanism leading to this phenomenon is quite well understood (see e.g. Laheurte et a1 1977). The van der Waals interactions between the wall and 3He or 4He atoms are equal, but 3He atoms occupy a larger volume because of their larger zero-point motion. One observes therefore a higher 4He concentration near a wall, which may induce a local superfluid ordering. This phenomenon was investigated by mean field techniques (Laheurte er a1 1977, Leibler and Peliti 1984), and by real space renormalisation group, applied to a semi-infinite version of the model introduced by Blume er a1 (1971, BEG) to describe He-4He mixtures (Peliti and Leibler 1984). While the results were encouraging, as far as agreement of the calculated phase diagram with the experimental one was concerned, this approach was unsatisfactory, since the BEG model mimics superfluid ordering (the breaking of a continuous U( 1) symmetry) via ferromagnetic ordering in a Ising-like system (the breaking of a discrete Z, symmetry). This is especially relevant for two-dimensional systems, like the film we are concerned with, because the Mermin-Wagner-Hohenberg theorem (see e.g. Hohenberg 1967) states that no spontaneous breaking of a continuous symmetry may take place in two dimensions. As a consequence, the film is superfluid since it is in the low-temperature phase of a Kosterlitz-Thouless (KT) transition (see e.g. Kosterlitz 1980), and not because its order parameter is different from zero. (Recent high-quality measurements (McQueeney er a1 1984) have confirmed the apparentness of superfluid film formation, in a certain concentration range, to the KT universality class, putting into evidence the corresponding universal jump in superfluid density.) A similar problem arises in the description of twodimensional 3He-4He mixtures, and was solved by the introduction, due to Berker and

2025, Physical Review Letters

We present a study on the temperature dependence of the microscopic entanglement distance, the chain dimension, and the plateau modulus of poly(ethylene-propylene) alternating copolymer. The re- sults provide insight into the microscopic origin of entanglement constraints and favor packing and scal- ing models over the topological approach. Furthermore, these results are at variance with one of the basic relations of the Doi-Edwards theory of viscoelasticity which unites the elastic response of a polymer melt with the entanglement distance.

2025, Physical Review E

We present a comparison between finite differences schemes and a pseudospectral method applied to the numerical integration of stochastic partial differential equations that model surface growth. We have studied, in 1+1 dimensions, the Kardar, Parisi and Zhang model (KPZ) and the Lai, Das Sarma and Villain model (LDV). The pseudospectral method appears to be the most stable for a given time step for both models. This means that the time up to which we can follow the temporal evolution of a given system is larger for the pseudospectral method. Moreover, for the KPZ model, a pseudospectral scheme gives results closer to the predictions of the continuum model than those obtained through finite difference methods. On the other hand, some numerical instabilities appearing with finite difference methods for the LDV model are absent when a pseudospectral integration is performed. These numerical instabilities give rise to an approximate multiscaling observed in the numerical simulations. With the pseudospectral approach no multiscaling is seen in agreement with the continuum model.

2025

Chiral electroweak anomalies predict baryon (B) and lepton (L) violating fermion interactions, which can be dressed with large numbers of Higgs and gauge bosons. The estimation of the total B + L-violating rate from an initial two-particle state — potentially observable at colliders — has been the subject of an intense discussion, mainly centered on the resummation of boson emission, which is believed to contribute to the cross-section with an exponential function of the energy, yet with an exponent (the “holygrail” function) which is not fully known in the energy range of interest. In this article we focus instead on the effect of fermions beyond the Standard-Model (SM) in the polynomial contributions to the rate. It is shown that B+L processes involving the new fermions have a polynomial contribution that can be several orders of magnitude greater than in the SM, for high centre-of-mass energies and light enough masses. We also present calculations that hint at a simple dependence...

2025, Journal of Low Temperature Physics

Babkin et aI have Jbund a small curvature in facets of 4He crystals. As a possible explanation they consider a model where the curvature arises from thermally activated defects previously studied by Andreev. We criticize this model, and... more

2025, Physical Review Letters

We present a refractive-index-matched colloidal system that allows direct observation of critical Casimir induced aggregation with a confocal microscope. We show that in this system, in which van der Waals forces are negligible, a simple competition between repulsive screened Coulomb and attractive critical Casimir forces can account quantitatively for the reversible aggregation. Above the temperature T a , the critical Casimir force drives aggregation of the particles into fractal clusters, while below T a , the electrostatic repulsion between the particles breaks up the clusters, and the particles resuspend by thermal diffusion. The aggregation is observed in a remarkably wide temperature range of as much as 15 . We derive a simple expression for the particle pair potential that accounts quantitatively for the temperature-dependent aggregation and aggregate breakup.

2025, Physical Review Letters

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2025, International Letters of Chemistry, Physics and Astronomy

Using the Mean-field theory based on Bogoliubov inequality for the free energy, a ferrimagnetic mixed spin-3/2 and spin-5/2 Ising model with different anisotropies is investigated. The free energy of a mixed spin Ising ferrimagnetic system from MF approximation of the Hamiltonian is calculated. By minimizing the free energy, we obtain the equilibrium magnetizations and compensation points. In particular, we investigate the effect of a single-ion anisotropy on the magnetic properties including the compensation phenomenon, in order to clarify the characteristic behaviours in a series of molecular-based magnets . The phase diagram of the system is also discussed in the anisotropy dependence of transition temperature. Our results of this model predict the existence of many (two or three) compensation points in the ordered system on a simple cubic lattice.

2025, Physical Review E

We present a self-organized stochastic model for the dynamics of a single flux line in random media. The dynamics for the flux line in the longitudinal and the transversal direction to an averaged moving direction are coupled to each other. The roughness exponents of the flux line are measured for each direction, which are close to α ≈ 0.63 for the longitudinal and α ⊥ ≈ 0.5 for the transversal direction, respectively. The dynamic exponents are obtained as z ≈ 1 for both directions. We discuss the classification of universality for the stochastic model.

2025, Acta Materialia

Mechanical twinning has long been recognized as an important deformation mechanism in many intermetallics including g(TiAl) based alloys. The generation of a twin can be triggered by dislocations at grain boundaries. The reduction of the stored strain energy in relation to a configuration without any twins can be shown by applying an established transformation criterion, considering twinning as a transformation shearing process. In addition, the application of a thermodynamical extremal principle allows one to predict a distinct twin nucleus in good agreement with experimental observations. The concept is rather general and can be adapted to any initial eigenstress field produced by dislocations present at misfitting interfaces.

2025, Order, Disorder and Criticality

2025, Physical Review Letters

We study the critical exponents of the superconducting phase transition in the context of renormalization group theory starting from a dual formulation of the Ginzburg-Landau theory. The dual formulation describes a loop gas of Abrikosov ux tubes which proliferate when the critical temperature is approached from below. In contrast to the Ginzburg-Landau theory, it has a spontaneously broken global symmetry and possesses an infrared stable xed point. The exponents coincide with those of a super uid with reversed temperature axis. 7440, 6470

2025, Europhysics Letters (EPL)

By using a heterodyne two-cross-beam configuration, we develop a new light scattering technique to study critical fluctuations. This optical arrangement gives the possibility to measure the critical dependence of both the intensity linewidth and the correlation function of the phase time derivative, in SF 6 near its gas-liquid critical point. We showed both experimentally and theoretically that the critical behaviour of the phase time derivative correlation function is determined by the thermodiffusive mode critical dependence, similar to the intensity linewidth. A good agreement between the experimental results and the theory is found.

2025, Physica A: Statistical Mechanics and its Applications

In the past five to ten years mounting evidence has arisen indicating that the large-scale spatial number density of galaxies may be governed by fractal or multifractal statistics. In this paper we extend this idea by searching for multifractal behaviour in other density fields. Namely, generalized luminosity density fields (which we define here) constructed from information on both the angular position and the apparent luminosity of galaxies. Using data from the Center for Astrophysics' CfA2 catalogue, we perform various multifractal analyses that reveal that over broad angular scales, the fields studied present two important signatures of multifractal behavior: multiscaling and algebraic probability distributions associated with extreme fluctuations and first-order multifractal phase transitions. Since the presence of both of these phenomena is the defining feature of Self-Organized Criticality, we argue that the spatio-luminous distribution of galaxies in the observable universe may be described as a nonclassical self-organized critical phenomenon resulting from multifractal cascades.

2025

The Teoria Gravito-Informațională Universală (TGIU) offers a novel framework for understanding spacetime collapse through informational gradients, entropy dynamics, and 2D-3D geometric transitions. While previous approaches such as BKL (Belinski-Khalatnikov-Lifshitz), Mixmaster (Misner), and AdS/CFT chaos models offer partial insights into black hole interiors and singularities, TGIU unifies these dynamics within a broader, simpler, and visually coherent structure. This paper shows how TGIU subsumes these earlier models as local manifestations of a larger, relational gravitational collapse architecture governed by entropy gradients, memory states, and dimensional transitions. The simplicity of TGIU's equations and visual geometry renders it uniquely suited for future quantum gravity investigations, cosmic structure modeling, and energy-collapse technologies.

2025

In this paper, we will extend the fundamental group π1 from its context in topological spaces to the context of graphs. We will also give some examples of fundamental groups of certain graphs, e.g. Kn.

2025

The Pittsburgh Supercomputing Center (PSC) has created and maintains the web site for this project. The downloadable code distribution resulting from PSC's work is found in the Members Area of this web site.

2025, Canadian Mathematical Bulletin

This article discusses our recent proof that above eight dimensions the scaling limit of sufficiently spread-out lattice trees is the variant of super-Brownian motion calledintegrated super-Brownian excursion(ISE), as conjectured by Aldous. The same is true for nearest-neighbour lattice trees in sufficiently high dimensions. The proof, whose details will appear elsewhere, uses the lace expansion. Here, a related but simpler analysis is applied to show that the scaling limit of a mean-field theory is ISE, in all dimensions. A connection is drawn between ISE and certain generating functions and critical exponents, which may be useful for the study of high-dimensional percolation models at the critical point.

2025, Physical review

The special surface transition at (2+1)-dimensional quantum critical point is precluded in corresponding classical critical point. The mechanism of such behavior which is only found in dimerized Heisenberg models so far is still under debate. To illuminate the role of symmetry protected topological (SPT) phase in inducing such nonordinary behaviors, we study a system on a two-dimensional square lattice consisted by interacting spin-1 Haldane chains, which has a genuine SPT phase-the Haldane phase-at weak interchain interactions and a quantum critical point belonging to the classical 3D O(3) universality class to the Néel phase. Different from models studied previously, there is no dimerization in the current model. Cutting the system along the chain direction or perpendicular to the chain direction exposes two different surfaces. Using unbiased quantum Monte Carlo simulations, we find that the two different types of surface show completely different surface critical behaviors at the bulk critical point, resulted from different surface states in the SPT phase. For the system with surfaces along the chain direction, the surface critical behavior is of ordinary type of the bulk 3D O(3) critical point, while for the surfaces perpendicular to the chain direction, the surface critical behavior is nonordinary, consistent with special transitions found in dimerized Heisenberg models. Our numerical results demonstrate that the gapless surface state in the gapped SPT phase together with the gapless mode of critical point is a pure quantum scenario that leads to the nonordinary transition.

2025, Physical Review Letters

Surface critical behavior (SCB) refers to the singularities of physical quantities on the surface at the bulk phase transition. It is closely related to and even richer than the bulk critical behavior. In this work, we show that three types of SCB universality are realized in the dimerized Heisenberg models at the (2+1)-dimensional O(3) quantum critical points by engineering the surface configurations. The ordinary transition happens if the surface is gapped in the bulk disordered phase, while the gapless surface state generally leads to the multicritical special transition, even though the latter is precluded in classical phase transitions because the surface is in the lower critical dimension. An extraordinary transition is induced by the ferrimagnetic order on the surface of the staggered Heisenberg model, in which the surface critical exponents violate the results of the scaling theory and thus seriously challenge our current understanding of extraordinary transitions.

2025, arXiv (Cornell University)

Continuous phase transitions exhibit richer critical phenomena on the surface than in the bulk, because distinct surface universality classes can be realized at the same bulk critical point by tuning the surface interactions. The exploration of surface critical behavior provides a window looking into higher-dimensional boundary conformal field theories. In this work, we study the surface critical behavior of a two-dimensional (2D) quantum critical Heisenberg model by tuning the surface coupling strength, and discover a direct special transition on the surface from the ordinary phase into an extraordinary phase. The extraordinary phase has a long-range antiferromagnetic order on the surface, in sharp contrast to the logarithmic decaying spin correlations in the 3D classical O( ) model. The special transition point has a new set of critical exponents, y s = 0.86(4) and η = -0.33(1), which are distinct from the special transition of the classical O(3) model and indicate a new surface universality class of the 3D O(3) Wilson-Fisher theory.

2025, arXiv (Cornell University)

2025, Physical Review B

2025, Physical Review Letters

2025, AIP Conference Proceedings

We review our work on a discrete model of stochastic, phase-coupled oscillators that is sufficiently simple to be characterized in complete detail, lending insight into the universal critical behavior of the corresponding nonequilibrium phase transition to macroscopic synchrony. In the mean-field limit, the model exhibits a supercritical Hopf bifurcation and global oscillatory behavior as coupling eclipses a critical value. The simplicity of our model allows us to perform the first detailed characterization of stochastic phase coupled oscillators in the locally coupled regime, where the model undergoes a continuous phase transition which remarkably displays signatures of the XY equilibrium universality class, verifying recent analytical predictions. Finally, we examine the effects of spatial disorder and provide analytical and numerical evidence that such disorder does not destroy the capacity for synchronization.

2025, arXiv (Cornell University)

In a numerical Monte Carlo simulation of SU(2) Yang-Mills theory with dynamical gauginos we find evidence for two degenerate ground states at the supersymmetry point corresponding to zero gaugino mass. This is consistent with the expected... more

2025, Physical Review B

The properties of monolayer and multilayer deposits of N2 on graphite are calculated using a pattern optimization of the total lattice energy and a Monte Carlo procedure with continuously deformable periodic boundary conditions. It is confirmed that the monolayer ground state is a 2&3)& &3 registered in-plane herringbone structure and the molecular orientations with respect to the substrate are in good agreement with experiment, as is the predicted orientational orderdisorder transition at T =25+2 K. As the surface density is increased above its registered value (p=1), a uniaxial incommensurate (UI) phase is found which persists until p-1.06, at which point the monolayer is in coexistence with the bilayer. The top layer of this bilayer, whichis complete at p=2. 2, forms a "pinwheel" structure much like the (111) plane of bulk e-Nq, and the bottom layer is a somewhat distorted herringbone. It is established that the common tangent between the UI monolayer and the bilayer does not intercept the monolayer pinwheel phase, which is therefore never physically realized. It is also shown that the bilayer, trilayer, and bulk are essentially in coexistence with one another and thus bulk formation should occur at densities above bilayer com- pletion.

2025, Physical Review B

We have investigated the phases of the Sn/ Si͑111͒-͑ ͱ 3 ϫ ͱ 3͒R30°surface below 1 3 ML coverage at room temperature by means of atomic force microscopy ͑AFM͒ and density functional theory based first-principles calculations. By tuning the Sn concentration at the surface we have been able to discriminate between Sn and Si adatoms, and to assure that the AFM topography for the different phases resembles the one reported using scanning tunneling microscopy. In the mosaic and the intermediate phases, a dependence of the topographic height of the Si adatoms on the number of surrounding Sn adatoms has been identified. In the pure phase, however, variations in the measured height difference between the Sn adatoms and the substitutional Si defects, which are intrinsic to the AFM observation, are reported. Reliable room-temperature force spectroscopic measurements using the atom-tracking technique and first-principles calculations provide an explanation for these striking induced height variations on the pure phase in terms of both the different strength of the short-range chemical interaction and tip-induced atomic relaxations. Our results suggest that the corrugation measured with true atomic resolution AFM operated at low interaction forces and close to the onset of significant short-range chemical interactions provides direct access to the real structure of heterogeneous semiconductor surfaces.

2025, Physica D: Nonlinear Phenomena

We describe the formation and evolution of spatial and temporal patterns in cylindrical premixed flames. We consider the cellular regime, Le < 1, where the Lewis number Le is the ratio of thermal to mass diffusivity of a deficient component of the combustible mixture. A transition from stationary, axisymmetric flames to stationary cellular flames is predicted analytically if Le is decreased below a critical value. We present the results of numerical computations to show that as Le is further decreased, with all other parameters fixed, traveling waves (TWs) along the flame front arise via an infiniteperiod bifurcation which breaks the reflection symmetry of the cellular array. Upon further decreasing Le we find the development of different kinds of periodically modulated traveling waves (MTWs) as well as a branch of quasiperiodically modulated traveling waves (QPMTWs). These transitions are accompanied by the development of different spatial and temporal symmetries including period doublings and period halvings in appropriate coordinate systems. We also observe the apparently chaotic temporal behavior of a disordered cellular pattern involving creation and annihilation of cells. We analytically describe the stability of the TW solution near its onset using suitable phase-amplitude equations. Within this framework one of the M T W 's can be identified as a localized wave traveling through an underlying stationary, spatially periodic structure.

2025, AIChE Journal

The progress in predicting critical transitions in fluid mixtures is reviewed. The critical state provides a valuable insight into the general phase behavior of a fluid and is closely linked with the nature and strength of intermolecular interaction. Calculations of critical equilibria have been confined mainly to binary mixtures. The prediction of binary gas‐liquid critical properties was initially limited to empirical correlations. These techniques have been superseded by rigorous calculations of the critical conditions using realistic models of the fluid or equations of state. All of the known types of critical phenomena exhibited by binary mixtures can be, at least, qualitatively calculated. If an optimal combining rule parameter is allowed, continuous gas‐liquid properties can be calculated accurately for a wide variety of mixtures. Similarly, the pressure and composition dependence of upper critical solution phenomena can be accurately predicted. Progress has been achieved in ...

2025, arXiv (Cornell University)

In this work, we have studied the effect of higher order perturbations, particularly the second order in details, on the sonic horizon. We have considered two different schemes of perturbations which are velocity potential perturbation and mass acceleration rate perturbation. These two schemes give us qualitatively similar behaviour. We have found that the analogue gravity formalism also holds for the higher order perturbations.

2025, Physical Review Letters

We have investigated the recently reported structural phase transition at low temperature (LT) for -Pb=Ge111 [from a (3 3) symmetry to a disordered phase] using scanning tunneling microscopy (STM). By tracking exactly the same surface regions with atomic resolution while varying the sample temperature from 40 to 140 K, we have observed that substitutional point defects are not mobile, in clear contrast to previous assumptions. Moreover, STM data measured at the lowest temperatures ever reported for this system (10 K) show that while filled-state images display the apparent signature of a glassy phase with no long-range order, in empty-state images honeycomb patterns with (3 3) periodicity, and not distinguishable from data measured at much higher temperatures, are clearly resolved. These new observations cast serious doubts on the nature and/or on the existence of a disordered phase at LT.

2025, Practical Fruits of Econophysics

A phenomenon of the financial log-periodicity is discussed and the characteristics that amplify its predictive potential are elaborated. The principal one is self-similarity that obeys across all the time scales. Furthermore the same preferred scaling factor appears to provide the most consistent description of the market dynamics on all these scales both in the bull as well as in the bear market phases and is common to all the major markets. These ingredients set very desirable and useful constraints for understanding the past market behavior as well as in designing forecasting scenarios. One novel speculative example of a more detailed S&P500 development until 2010 is presented.

2025

behavior of weakly-disordered anisotropic systems in two dimensions

2025

Bianchi Type V inflationary cosmological model with massless scalar field and flat potential and decaying vacuum energy density is investigated. To get the deterministic solution in terms of cosmic time t, we assume that the decaying vacuum energy density where R is scale factor, α a constant, we find that the spatial volume increases exponentially indicating the inflationary scenario in the model. The model represents decelerating and accelerating phases both which matches with the recent astronomical observations. The anisotropy is maintained throughout in the model. However, for large values of time (T), the model isotropizes, where T is rescaling of cosmic time t. The rate of Higgs field decreases slowly with time. The model has Point Type Singularity at T = 0. (MacCallum(1971))

2025

String dust cosmological model for barotropoic fluid distribution with vacuum energy density in the frame work of FRW space-time is investigated. The model starts with a big-bang at  = 0 and the expansion in the model decreases with time. The spatial volume increases with time representing inflationary scenario. The vacuum energy density 2     which matches with the result as obtained by Bertolami [10]. The energy density and string tension density are initially large but decreases with time. The model also represents decelerating phase of universe. The special cases for dust model (p = 0), radiation dominated model and stiff fluid model are also discussed.

2025, Journal of physics

The Hamiltonian dynamics of the classical ϕ 4 model on a two-dimensional square lattice is investigated by means of numerical simulations. The macroscopic observables are computed as time averages. The results clearly reveal the presence of the continuous phase transition at a finite energy density and are consistent both qualitatively and quantitatively with the predictions of equilibrium statistical mechanics. The Hamiltonian microscopic dynamics also exhibits critical slowing down close to the transition. Moreover, the relationship between chaos and the phase transition is considered, and interpreted in the light of a geometrization of dynamics.

2025, International Journal of Geometric Methods in Modern Physics

We present the analytic Lifshitz solutions for a scalar field model minimally coupled with the abelian gauge field in N dimensions. We also consider the presence of cosmological constant Λ. The Lifshitz parameter z appearing in the solution plays the role of the Lorentz breaking parameter of the model. We investigate the thermodynamical properties of the solutions and discuss the energy issue. Furthermore, we study the hairy black hole solutions in which the abelian gauge field breaks the symmetry near to the horizon. In the holographic picture, it is equivalent to a second order phase transition. Explicitly we show that there exists a critical temperature which is a function of the Lifshitz parameter z. The system below the critical temperature becomes superconductor, but the critical exponent of the model remains the same of the usual holographic superconductors without the higher order gravitational corrections, in agreement with Ginzburg-Landau theories.

2025, arXiv (Cornell University)

We present the analytic Lifshitz solutions for a scalar field model minimally coupled with the abelian gauge field in NNN dimensions. We also consider the presence of cosmological constant Lambda\LambdaLambda. The Lifshitz parameter zzz appearing in the solution plays the role of the Lorentz breaking parameter of the model. We investigate the thermodynamical properties of the solutions and discuss the energy issue. Furthermore, we study the hairy black hole solutions in which the abelian gauge field breaks the symmetry near the horizon. In the holographic picture, it is equivalent to a second order phase transition. Explicitly we show that there exists a critical temperature which is a function of the Lifshitz parameter zzz. The system below the critical temperature becomes superconductor, but the critical exponent of the model remains the same of the usual holographic superconductors without the higher order gravitational corrections, in agreement with Ginzburg-Landau theories.

2025, Nuclear Physics A

This report summarizes the presentations and discussions during the Rapid Reaction Task Force "Dynamics of critical fluctuations: Theory -phenomenology -heavy-ion collisions", which was organized by the ExtreMe Matter Institute EMMI and held at GSI, Darmstadt, Germany in April 2019. We address the current understanding of the dynamics of critical fluctuations in QCD and their measurement in heavy-ion collision experiments. In addition, we outline what might be learned from studying correlations in other physical systems, such as cold atomic gases.