Physical properties of compact star-like systems harboring traversable wormholes: Effects of chaotic magnetic fields and anisotropic matter

summary

The gist

Neutron-star–wormhole (NSWH) systems supported by two scalar fields are formulated to investigate how chaotic magnetic fields and pressure anisotropy affect their mass, radius, surface redshift,

In short

This research investigates neutron-star–wormhole systems using two scalar fields to see how chaotic magnetic fields and matter anisotropy affect their properties. The study finds that these complex factors can create extremely massive configurations exceeding 8 solar masses and surface redshifts above 1.5, showing a dependence of the gravitational-wave echo time on the magnetic field strength.

Key concepts

Anisotropy Term ($\sigma$): This term quantifies the difference between tangential pressure ($p_t$) and radial pressure ($p_r$) within the neutron fluid. It is crucial because it modifies the standard Tolman-Oppenheimer-Volkoff equation, allowing researchers to model how the internal structure of a compact star deviates from simple isotropic models.
Chaotic Magnetic Field Approximation: The model incorporates chaotic magnetic fields by assuming that the magnetic pressure ($p_a$) is related to the magnetic field strength ($B$) through an effective isotropic pressure formula. This simplification allows the complex magnetic effects to be consistently included within a spherically symmetric mathematical framework.
Violation of Energy Conditions (NEC): The traversable nature of the wormhole geometry is guaranteed by violating energy conditions, specifically the Null Energy Condition (NEC), near the throat. This violation means that standard physical assumptions about energy density and pressure are not met in that region, which is necessary to maintain a stable, traversable wormhole.
Surface Redshift ($z$): Surface redshift measures how much gravity affects light escaping from the surface of the compact object. The calculation shows that these systems can exhibit very high redshifts (up to $z \simeq 1.5$), which is significantly larger than what is expected for normal neutron stars.

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This episode discusses

The paper

Physical properties of compact star-like systems harboring traversable wormholes: Effects of chaotic magnetic fields and anisotropic matter · Read on arXiv

Theoretical High Energy Physics Group, Department of Physics, Institut Teknologi Bandung · Indonesia Center for Theoretical and Mathematical Physics (ICTMP), Institut Teknologi Bandung · Research Center for Quantum Physics, National Research and Innovation Agency (BRIN), South Tangerang · High Energy Physics Theory Group, Department of Physics, Faculty of Science, Chulalongkorn University · Department of Physics and Astronomy, University of Waterloo · Perimeter Institute for Theoretical Physics, Waterloo

In this paper, we formulate exotic compact objects in form of compact star-like systems harboring traversable wormhole (CSSTW) supported by two scalar fields, allowing for both chaotic magnetic field and pressure anisotropy of the neutron fluid. The wormhole is traversable regardless of whether anisotropy of the neutron fluid and/or magnetic fields are included. In particular, the null energy condition (NEC) remains violated in the vicinity of the wormhole throat, ensuring the traversable nature of the geometry. The Kretschmann scalars for all considered configurations show that the entire spacetime is regular. The temporal metric functions for all considered configurations show that there are no horizons in any of the considered cases. For magnetized configurations, the resulting CSSTW can become extremely massive, with ADM masses exceeding 8,M, and can exhibit large surface redshifts exceeding Z 1.5. The system can also reach the ultracompact regime, which allows us to calculate echo time that might be produced the systems. Our calculations of the echo time indicate that it can vary depending on the chaotic magnetic field configuration and fluid anisotropy. For non-magnetized configurations, the gravitational-wave echo time is of the order of 10-2-10-1 ms. For the magnetized configurations, however, it ranges from the order of 10-1 μ s-10-1 ms, suggesting that magnetic fields broaden the range of echo time. Moreover, to investigate the direct impact of the magnetic field on the echo time, we derive an explicit expression for the echo time as a function of uniform magnetic field. The resulting relation shows that the echo time decreases as the magnetic field strength increases. The stability analysis of radial perturbations shows that all considered configurations with a surface magnetic field of B s=10 15 G are stable.

Transcript

Introduction to the show: ident: Astrophysics Radio. Generated commentary on the latest astrophysics papers.

Vera: Today's paper: "Physical properties of compact star-like systems harboring traversable wormholes".

Jocelyn: Neutron-star–wormhole (NSWH) systems supported by two scalar fields are formulated to investigate how chaotic magnetic fields and pressure anisotropy affect their mass, radius, surface redshift, and gravitational-wave echo time.

Vera: First, who's behind it and why it matters.

Paper summary: Vera: To summarize what this paper is about, "Physical properties of compact star-like systems harboring traversable wormholes: Effects of chaotic magnetic fields and anisotropic matter" form a model for NSWH systems using two scalar fields to investigate how chaotic magnetic fields and pressure anisotropy impact their mass, radius, surface redshift, and gravitational-wave echo time.

Jocelyn: They are essentially looking at how the anisotropy of the neutron fluid and the presence of chaotic magnetic fields alter these key physical properties. It claims that these effects can result in very massive configurations exceeding eight solar masses and surface redshifts greater than one point five, while also showing a dependence of the echo time on magnetic field strength.

Subrahmanyan: The core thesis seems to be that this formulation allows them to explore how these non-trivial physical inputs can drive the system into regimes with significantly altered macroscopic behavior, which is important for understanding exotic compact objects in the cosmos.

Vera: It matters because it challenges our previous understandings of what's physically possible within these hybrid systems, especially concerning their mass limits and how they would appear as gravitational wave echoes.

Jocelyn: And the way they handle the constraints—using Lagrange multipliers to eliminate ghosts—is a key part of establishing a valid formalism for these traversable geometries.

Subrahmanyan: The authors are addressing prior work that struggled with ghost instabilities, and this paper builds upon that by incorporating the anisotropy of the fluid as well, which they say was previously overlooked in similar formalisms.

Conclusion: Vera: Thinking about the title, "Physical properties of compact star-like systems harboring traversable wormholes: Effects of chaotic magnetic fields and anisotropic matter," it really captures the complexity they are tackling here with neutron-star–wormhole systems. The authors are Pattersonsa, Zena, Prihadic, and Saktid.

Jocelyn: And what's really striking is how they connect these microscopic details—the chaotic magnetic fields and fluid anisotropy—to macroscopic observables like the surface redshift and echo time. It shows that these internal properties matter a lot to what we actually measure from astrophysical events.

Subrahmanyan: The implication is that when we look for evidence of exotic environments, we can't just assume a simple, uniform fluid or field; the details of how matter is distributed and magnetized fundamentally shape the observable outcomes like the mass-radius relation they derived.

Vera: So, in simpler terms, this paper suggests that these complex physical ingredients don't just add noise; they create entirely different types of physical solutions for NSWH systems that we need to account for when interpreting any potential data we collect.

Jocelyn: And the finding about the echo time varying with magnetic field strength gives us a concrete prediction: if we observe an echo, the magnetic environment will tell us something specific about how strong it was.

Subrahmanyan: Ultimately, this work contributes to mapping out a broader landscape of possible compact objects, suggesting that incorporating realistic fluid dynamics and magnetic chaos is essential for building accurate theoretical models of these astrophysical phenomena.

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