International Journal of Theoretical Physics最新文献

In this paper, we investigate the influence of perfect fluid dark matter and quantum corrections on the thermodynamics of nonlinear magnetic-charged black hole. We consider the metric of the static nonlinear magnetic-charged black hole in the background of perfect fluid dark matter. Starting with the black hole temperature and the corrected entropy, we use the event horizon propriety in order to find the temperature, and based on the surface gravity definition, we find the uncorrected entropy. However, using the definition of the corrected entropy due to thermal fluctuation, we find and plot the entropy of the black hole. We find that the entropy is affected for smaller nonlinear magnetic-charged black holes. Afterwards, we study the thermodynamic stability of the black hole by computing and plotting the evolution of heat capacity. The results show that second-order phase transition occurs, which appears more later as the dark matter parameter decreases, and leads the black hole to move from the stable phase to the unstable phase. Furthermore, we show that the heat capacity for smaller black holes are also affected, since it appears not being only an increasing function. We also find that the behavior of Gibbs energy is modified when taking into account quantum corrections.

Spin network technique is usually generalized to relativistic case by changing SO(varvec{(4)}) group – Euclidean counterpart of the Lorentz group – to its universal spin covering SU(varvec{(2)}times ) SU(varvec{(2)}), or by using the representations of SO(varvec{(3,1)}) Lorentz group. We extend this approach by using inhomogeneous Lorentz group (varvec{mathcal {P}}= {varvec{SO}}varvec{(3,1)}rtimes mathbb {R}^4), which results in the simplification of the spin network technique. The labels on the network graph corresponding to the subgroup of translations (mathbb {R}^4) make the intertwiners into the products of SU(varvec{(2)}) parts and the energy-momentum conservation delta functions. This maps relativistic spin networks to usual Feynman diagrams for the matter fields.

In Kallosh and Linde (Phys. Rev. D 73, 104033 2006), Kallosh and Linde discussed the SLOCC classification of black holes. However, the criteria for the SLOCC classification of black holes have not been given. In addition, the LU classification of black holes has not been studied in the past. In this paper we will consider both SLOCC and LU classification of the STU black holes with four integer electric charges (q_{i} ) and four integer magnetic charges (p^{i}), (i=0,1,2,3). Two STU black holes with eight charges are considered SLOCC (LU) equivalent if and only if their corresponding states of three qubits are SLOCC (LU) equivalent. Under this definition, we give criteria for the classification of the eight-charge STU black holes under SLOCC and under LU, respectively. We will study the classification of the black holes via the classification of SLOCC and LU entanglement of three qubits. We then identify a set of black holes corresponding to the state W of three qubits, which is of interest since it has the maximal average von Neumann entropy of entanglement. Via von Neumann entanglement entropy, we partition the STU black holes corresponding to pure states of GHZ SLOCC class into five families under LU.

Two simultaneous quantum teleportation schemes are proposed by utilizing the four-qubit cluster state as quantum channels. In each scheme, there are three legitimate participants, that is one sender Alice and two receivers Bob and Chris. Taking advantage of the pre-shared quantum entanglement resources and some necessary local quantum operations as well as classical communication, Alice can concurrently transmit two independent unknown target quantum states to Bob and Chris, respectively. In the first scheme, the target states are two arbitrary single-qubit states, while in the second scheme they are two unknown multi-qubit entangled states. The proposed schemes are simply to implement because of requiring only single-qubit measurements and Pauli operations as well as two-qubit unitary operations.

Nonlinear partial differential equations (NLPDEs) are used in a wide range of natural and applied sciences phenomena. A fascinating and rapidly developing scientific field is the study of soliton solutions to nonlinear evolution equations (NLEEs). In this research, different types of soliton solutions for the strain wave model (SWM) are derived by using the F-expansion method (FEM) and the Bernoulli Sub-ODE method (BSODE) scheme. This equation plays an important role in engineering and mathematical physics. The acquired solutions in this work include compactons, bell-shaped soliton, dark, bright, kink soliton and periodic solutions. These precise solutions help researchers to understand the physical phenomena of this wave equation.

Secure computational geometry (SCG) is an important type of secure multi-party computation (SMC) problem, which studies how to calculate the relationship of several geometric objects securely. Quantum SCG (QSCG) can achieve higher security than classical SCG protocols, but the achievements of QSCG are still limited at present. In this paper, we define a new SCG problem: the secure clockwise sorting (SCS) problem, and propose a quantum protocol to solve it. We first propose a quantum secure clockwise comparison subprotocol, where the cross and scalar products of two vectors are calculated by using a quantum secure two-party scalar product protocol, and then the relative clockwise order of two points is determined. Based on the subprotocol, we then give a quantum SCS protocol to determine the clockwise order of a series of points. Finally, we show the correctness, security, and efficiency of our protocol through detailed performance analysis.

In this paper, we present a novel bidirectional quantum teleportation protocol facilitating the simultaneous teleportation of pairs of EPR and GHZ states through entanglement swapping within a six-qubit GHZ channel. This protocol leverages pre-existing GHZ states within the channel, alongside the EPR and GHZ states intended for teleportation, to generate a new entangled state. Subsequently, this state undergoes measurement by Alice and Bob, with the measurement outcomes determining the teleported states. Finally, the successful teleportation of the EPR and GHZ states to each other is ensured through the utilization of CNOT operators, single-qubit and two-qubit measurements, and the application of the identity operator. The proposed protocol presents several advantages over existing protocols, including its bidirectional nature and higher efficiency.

As a typical quantum many body problem, we consider the time evolution of density matrix elements in the Bose-Hubbard model. For an arbitrary initial state, these quantities can be obtained from an SDE or stochastic differential equation system. To this SDE system, a Girsanov transformation can be applied. This has the effect that all the information from the initial state moves into the drift part, into the mean field part, of the transformed system. In the large N limit with (g=UN) fixed, the diffusive part of the transformed system vanishes and as a result, the exact quantum dynamics is given by an ODE system which turns out to be the time dependent discrete Gross Pitaevskii equation. For the two site Bose-Hubbard model, the GP equation reduces to the mathematical pendulum and the difference of expected number of particles at the two lattice sites is equal to the velocity of that pendulum which is either oscillatory or it can have rollovers which then corresponds to the self trapping or insulating phase. As a by-product, we also find an equivalence of the mathematical pendulum with a quartic double well potential. Collapse and revivals are a more subtle phenomenom, in order to see these the diffusive part of the SDE system or quantum corrections have to be taken into account. This can be done with an approximation and collapse and revivals can be reproduced, numerically and also through an analytic calculation. Since expectation values of Fresnel or Wiener diffusion processes, we write the density matrix elements exactly in this way, can be obtained from parabolic second order PDEs, we also obtain various exact PDE representations. The paper has been written with the goal to come up with an efficient calculation scheme for quantum many body systems and as such the formalism is generic and applies to arbitrary dimension, arbitrary hopping matrices and, with suitable adjustments, to fermionic models.

Monogamy of entanglement is the fundamental property and inherent nature of quantum systems. We study the monogamy properties of two fidelity based entanglement measures, the Bures measure of entanglement and the geometric measure of entanglement. Stronger monogamy relations are presented for the (alpha )th ((alpha ge 2)) power and the (beta )th ((0le beta le eta , eta ge 1)) power of these two entanglement measures. Moreover, for the case of the (gamma )th ((gamma <0)) power, we give the corresponding upper bounds for the two entanglement measures. Detailed examples are provided to illustrate that our newly established monogamy relations are stronger than the previous ones.