搜索结果：Creation

We consider the quantum creation of a universe with flat spatial sections and the topology of a 3-torus, taking into account the effect of Casimir energy. We show that the corresponding instantons are singular. Since these instantons describe universes originating in a state of infinite energy, we argue that they cannot be interpreted as quantum creation from `nothing'. If quantum corrections to the energy-momentum tensor are neglected, the spacetime of the toroidal universe reduces to de Sitter space with appropriate periodic identifications. Contrary to previous claims in the literature, this spacetime is geodesically incomplete. We argue that this spacetime describes a classical universe originating at a singularity, and not a quantum origin. We conclude that the quantum creation of a toroidal universe from nothing cannot be described in the context of semiclassical quantum gravity -- it is either impossible, or it depends essentially on Planck-scale physics. We therefore see no reasonable way to compare the probability of creation of a toroidal universe, if it is possible at all, with that of a spherical universe.

We define creation and annihilation operators for any 2D non-abelian anyon theory by studying the algebraic structure from the anyon diagrammatic formalism. We construct the creation operators for Fibonacci anyons explicitly. We obtain that a single creation operator per particle type is not enough; we need an extra creation operator for every alternative fusion channel. We express any physically allowed observable in terms of these creation and annihilation operators. Finally, we express the 2D Fibonacci Hubbard Hamiltonian in terms of the Fibonacci creation and annihilation operators, and we comment on developing methods for simulation based on these creation and annihilation operators.

The term 'neutrinoless' is a cornerstone of modern particle physics, yet it defines a fundamental process by what is missing rather than what is created. We trace the origins of this privative neologism to a 1953 experimental claim and show how a 'sociology of suspicion' transformed Ettore Majorana's affirmative ontology into an agnostic shorthand. By examining this linguistic shift, we argue that our current terminology may obscure the profound physical meaning of the search. Reclaiming the language of 'matter creation' is not merely a semantic choice, but a timely conceptual shift to bridge the gap between experimental caution and the radical character of the laws of nature we aim to uncover.

Short review of the Weyl geometry is given. To describe the phenomenological particle creation we suggest the modified perfect fluid model taking into account the back reaction on the geometry of both the already created particles and the very process of their creation. It is found that the relation for particle creation is conformal invariant. This requires the creation law consisting of the source terms as the Weyl Lagrangian plus two quite new terms depending of the particle number density.

Creativity is a fundamental aspect of intelligence, involving the ability to generate novel and appropriate solutions across diverse contexts. While Large Language Models (LLMs) have been extensively evaluated for their creative capabilities, the assessment of Multimodal Large Language Models (MLLMs) in this domain remains largely unexplored. To address this gap, we introduce Creation-MMBench, a multimodal benchmark specifically designed to evaluate the creative capabilities of MLLMs in real-world, image-based tasks. The benchmark comprises 765 test cases spanning 51 fine-grained tasks. To ensure rigorous evaluation, we define instance-specific evaluation criteria for each test case, guiding the assessment of both general response quality and factual consistency with visual inputs. Experimental results reveal that current open-source MLLMs significantly underperform compared to proprietary models in creative tasks. Furthermore, our analysis demonstrates that visual fine-tuning can negatively impact the base LLM's creative abilities. Creation-MMBench provides valuable insights for advancing MLLM creativity and establishes a foundation for future improvements in multimodal generative

The process of electron-positron pair creation and oscillation in uniform electric field is studied, taking into account Pauli exclusion principle. Generally, we find that pair creation is suppressed, hence coherent oscillations occur on longer time scales. Considering pair creation in already existing electron-positron plasma we find that the dynamics depends on pair distribution function. We considered Fermi-Dirac distribution of pairs and found that for small temperatures pair creation is suppressed, while for small chemical potentials it increases: heating leads to enhancement of pair creation.

Ultra strong electromagnetic fields can lead to spontaneous creation of single or multiple electron-positron pairs. A quantum field theoretical treatment of the pair creation process combined with numerical methods provides a description of the fermionic quantum field state, from which all observables of the multiple electron-positron pairs can be inferred. This allows to study the complex multi-particle dynamics of electron-positron pair creation in-depth, including multi-pair statistics as well as momentum distributions and spin. To illustrate the potential benefit of this approach, it is applied to the intermediate regime of pair creation between nonperturbative Schwinger pair creation and perturbative multiphoton pair creation where the creation of multi-pair states becomes nonnegligible but cascades do not yet set in. Furthermore, it is demonstrated how spin and helicity of the created electrons and positrons are affected by the polarization of the counterpropagating laser fields, which induce the creation of electron-positron pairs.

Sauter-Schwinger pair creation in electromagnetic fields is a fundamental prediction of QED and one of the motivations for the present efforts in constructing super-strong lasers. I will give a historical review of the subject, and then focus on two recent developments. The first one is the worldline instanton formalism, a sophisticated version of the WKB approximation that makes it possible to calculate the pair creation rate for complicated field configurations. The second one is an adaptation of the Dirac-Heisenberg-Wigner formalism suitable for a detailed study of the formation of real particles in time and space.

We study the Nash equilibrium and the price of anarchy in the max-distance network creation game. Network creation game, first introduced and studied by Fabrikant et al., is a classic model for real-world networks from a game-theoretic point of view. In a network creation game with n selfish vertex agents, each vertex can build undirected edges incident to a subset of the other vertices. The goal of every agent is to minimize its creation cost plus its usage cost, where the creation cost is the unit edge cost $α$ times the number of edges it builds, and the usage cost is the sum of distances to all other agents in the resulting network. The max-distance network creation game, introduced and studied by Demaine et al., is a key variant of the original game, where the usage cost takes into account the maximum distance instead. The main result of this paper shows that for $α> 19$ all equilibrium graphs in the max-distance network creation game must be trees, while the best bound in previous work is $α> 129$. We also improve the constant upper bound on the price of anarchy to 3 for tree equilibria. Our work brings new insights into the structure of Nash equilibria and takes one st

We use digital quantum computing to simulate the creation of particles in a dynamic spacetime. We consider a system consisting of a minimally coupled massive quantum scalar field in a spacetime undergoing homogeneous and isotropic expansion, transitioning from one stationary state to another through a brief inflationary period. We simulate two vibration modes, positive and negative for a given field momentum, by devising a quantum circuit that implements the time evolution. With this circuit, we study the number of particles created after the universe expands at a given rate, both by simulating the circuit and by actual experimental implementation on IBM quantum computers, consisting of hundreds of quantum gates. We find that state-of-the-art error mitigation techniques are useful to improve the estimation of the number of particles and the fidelity of the state.

In this work, I analyze the structure of the QED spacetime lattice and review the Schwinger pair creation process from a thermodynamic point of view. This viewpoint enables the dynamical mean-field calculation for the 3 + 1 dimensional Schwinger pair creation with the backreaction. As an example, I demonstrate how to evaluate the pair creation in a finite volume with external electric fields turned on at $t = 0$. The numerical results show how the backreaction responds to the external fields and influences the pair creation.

We consider the Hilbert scheme of points in the affine complex plane. We find explicit formulas for the Nakajima's creation operators and their K-theoretic counterparts in terms of the Kirwan map. We obtain a description of the action of Nakajima's creation operators on the Chern classes of the tautological bundle.

The common tunneling picture of electron-positron pair creation in a strong electric field is generalized to pair creation in combined crossed electric and magnetic fields. This enhanced picture, being symmetric for electrons and positrons, is formulated in a gauge-invariant and Lorentz-invariant manner for quasistatic fields. It may be used to infer qualitative features of the pair creation process. In particular, it allows for an intuitive interpretation of how the presence of a magnetic field modifies and, in particular cases, even enhances pair creation. The creation of electrons and positrons from the vacuum may be assisted by an energetic photon, which can also be incorporated into this picture of pair creation.

We discuss the interconnection between the Schwinger pair creation in electric field, Hawking radiation and particle creation in the Unruh effect. All three processes can be described in terms of the entropy and temperature. These thermodynamic like processes can be combined. We consider the combined process of creation of charged and electrically neutral particles in the electric field, which combine the Schwinger and Unruh effects. We also consider the creation of the charged black and white holes in electric field, which combines the Schwinger effect and the black hole entropy. The combined processes obey the sum rules for the entropy and for the inverse temperature. Some contributions to the entropy and to the temperature are negative, which reflects the quantum entanglement between the created objects.

We study numerically two versions of the monopole creation operators proposed by Frohlich and Marchetti. The disadvantage of the old version of the monopole creation operator is due to visibility of the Dirac string entering the definition of the creation operator in the theories with coexisting electric and magnetic charges. This problem does not exist for the new creation operator which is rather complicated. Using the Abelian Higgs model with a compact gauge field we show that both definitions of the monopole creation operator can serve as order parameters for the confinement--deconfinement phase transition. The value of the monopole condensate for the old version depends on the length of Dirac string. However, as soon as the length is fixed the old operator certainly discriminates between the phases with condensed and non--condensed monopoles.

We study particle creation in the presence of bulk viscosity of cosmic fluid in the early universe within the framework of open thermodynamical systems. Since the first-order theory of non-equilibrium thermodynamics is non-causal and unstable, we try to solve the bulk viscosity equation of the cosmic fluid with particle creation through the full causal theory. By adopting an appropriate function for particle creation rate of "Creation of Cold Dark Matter" model, we obtain analytical solutions which do not suffer from the initial singularity and are in agreement with equivalent solutions of Lambda-CDM model. We constrain the free parameter of particle creation in our model based on recent Planck data. It is also found that the inflationary solution is driven by bulk viscosity with or without particle creation.

In this paper we describe the Bayesian link between the cosmological mass function and the distribution of times at which isolated halos of a given mass exist. By assuming that clumps of dark matter undergo monotonic growth on the time-scales of interest, this distribution of times is also the distribution of `creation' times of the halos. This monotonic growth is an inevitable aspect of gravitational instability. The spherical top-hat collapse model is used to estimate the rate at which clumps of dark matter collapse. This gives the prior for the creation time given no information about halo mass. Applying Bayes' theorem then allows any mass function to be converted into a distribution of times at which halos of a given mass are created. This general result covers both Gaussian and non-Gaussian models. We also demonstrate how the mass function and the creation time distribution can be combined to give a joint density function, and discuss the relation between the time distribution of major merger events and the formula calculated. Finally, we determine the creation time of halos within three N-body simulations, and compare the link between the mass function and creation rate with

Cosmological evolution driven incorporating continuous particle creation by the time-varying gravitational field is investigated. We consider a spatially flat, homogeneous and isotropic universe with two matter fluids in the context of general relativity. One fluid is endowed with gravitationally induced `adiabatic' particle creation, while the second fluid simply satisfies the conservation of energy. We show that the dynamics of the two fluids is entirely controlled by a single nonlinear differential equation involving the particle creation rate, $Γ(t)$. We consider a very general particle creation rate, $Γ(t)$, that reduces to several special cases of cosmological interest, including $Γ=$ constant, $% Γ\propto 1/H^{n}$ ($n\in \mathbb{N}$), $Γ\propto \exp (1/H)$. Finally, we present singular algebraic solutions of the gravitational field equations for the two-fluid particle creation models and discuss their stability.

I consider a truncation of low-energy string theory which contains two $U(1)$ gauge fields. After making some general comments on the theory, I describe a previously-obtained instanton for the pair creation of black holes when both gauge fields are non-zero, and obtain the pair creation rate by calculating its action. This calculation agrees qualitatively with the earlier calculation of the pair creation rate for black holes in Einstein-Maxwell theory. That is, the pair creation is strongly suppressed in realizable circumstances, and it reduces to the Schwinger result in the point-particle limit. The pair creation of non-extreme black holes is enhanced over that of extreme black holes by $e^{{\cal A}_{bh}/4}$.