Skip to Content
  • 2.5
    Impact Factor
  • 5.0
    CiteScore
  • 21 days
    Submission to First Decision
  • 3 days
    Acceptance to Publication
  • Congratulations to Prof. Roger Penrose, Advisory Board member of Universe, for receiving the Nobel Prize in Physics 2020.

Universe

Universe is a peer-reviewed, open access journal focused on theoretical, experimental, and observational progress in fundamental and applied physics, from circumterrestrial space to cosmological scenarios, and is published monthly online by MDPI.

Get Alerted

Add your email address to receive forthcoming issues of this journal.

All Articles (3,643)

  • Article
  • Open Access

We investigate the background dynamics of cubic Geometric Inflation coupled with radiation and a minimally coupled canonical scalar field with an exponential potential, using the cubic truncation as a minimal test of geometric-to-scalar inflationary cascades. We formulate the cosmological equations as an autonomous dynamical system and analyze its finite critical points and representative Hubble-flow trajectories. The cubic sector can generate an initial geometrically accelerated phase, but its duration grows only logarithmically with the initial curvature hierarchy and is insufficient to solve the horizon problem for moderate initial conditions. The subsequent scalar-field-dominated stage obeys the power-law relation under the standard GR-based first-order mapping, placing it in strong tension with current bounds on primordial tensor modes. Moreover, no value of the constant exponential-potential slope yields a graceful exit into a standard radiation-dominated epoch. The regular branch requires trans-Planckian radiation densities in the asymptotic past, whereas the alternative branch contains a finite-curvature dynamical degeneracy. Thus, although cascade-like background trajectories exist, the minimal cubic model does not satisfy the basic background requirements of a viable inflationary cosmology.

Universe

15 October 2026

Phase-space portraits of the autonomous system (66)–(68) for the regular positive branch, 
  
    s
    =
    +
    1
  
. The upper row shows the three-dimensional phase-space trajectories, while the lower row shows their corresponding projections on the x–z plane. Panels (a,d) correspond to 
  
    γ
    =
    0
  
, panels (b,e) to 
  
    γ
    =
    1
  
, and panels (c,f) to 
  
    
      γ
      2
    
    =
    4.2
  
. In particular, the plotted region in (b) should be understood as a finite visualization window rather than as the full physical phase space. Since the 
  
    s
    =
    +
    1
  
 domain is non-compact in the scalar variables as 
  
    x
    →
    
      1
      −
    
  
, some relevant asymptotic boundary configurations can lie outside the displayed box. For example, for 
  
    γ
    =
    1
  
, 
  
    P
    
      g
      ϕ
    
  
 has 
  
    z
    ≃
    1.02
  
, slightly outside the plotted interval. The dynamical trajectories are shown in blue, the critical points are marked by red spheres, and the reddish-orange surface corresponds to 
  
    q
    =
    0
  
, which separates accelerated and decelerated regions of the phase space. This surface is determined by the relation 
  
    
      u
      2
    
    −
    2
    
      z
      2
    
    =
    −
    1
    +
    
      
        
          s
          x
        
        
          1
          −
          x
        
      
    
  
. For the first two cases, with 
  
    
      γ
      2
    
    ≤
    4
  
, the model exhibits a cascade-like behavior, whereas for 
  
    
      γ
      2
    
    >
    4
  
, the trajectories approach a decelerated radiation-scalar scaling regime.
  • Article
  • Open Access

This study presents Solar Cycle (SC) 25 (2020–2025) results from the homogeneous Kanzelhöhe Solar Observatory (KSO) catalogue project and completes the analysis of SCs 19–25. Only SC18 remains to be processed before the catalogue is finalized. Using KSO white-light observations, we determined sidereal rotation velocities and solar differential rotation (DR) parameters A and B from day-to-day positional changes in sunspot-groups and from robust linear fits to their position–time measurements. Their temporal evolution and relationship with solar activity were analyzed using yearly mean Solar Index and Long-term Solar Observations (SILSO) sunspot numbers. Rotation velocity residuals were also analyzed as a function of time and heliographic latitude in search of possible torsional oscillation (TO) signatures. The obtained DR parameters are consistent with previously published results. For SC25, a strong anticorrelation between the yearly fitted parameters A and B was found, in agreement with earlier studies, although its interpretation is affected by the covariance between the two parameters introduced by the fitting procedure. The residual rotation velocities exhibit temporal behaviour similar to that reported in previous sunspot-group studies. Latitude–time residual maps reveal patterns that may represent TO signatures, however the limited temporal coverage of SC25, the characteristics of sunspot group tracers, and the use of interpolated data require a cautious interpretation.

Universe

13 October 2026

Dependence of sidereal rotation velocities on heliographic latitude for SC25 (2020–2025), i.e., solar DR profiles derived from Kanzelhöhe Solar Observatory (KSO) sunspot-group positions measured in white-light images and listed in the last row of Table 1. For the calculation of sidereal velocities daily shift (DS) and robust linear least-squares (rLSQ) methods have been used (top and bottom panels, respectively).
  • Article
  • Open Access

Radiative Corrections and Reheating in Supergravity Models of Inflation

  • John Ellis,
  • Tony Gherghetta and
  • Keith A. Olive
  • + 2 authors

We consider the effects of radiative corrections in Starobinsky-like models of inflation, concentrating on models of inflation formulated in N=1 no-scale supergravity. Inflaton couplings with matter fields are necessary for reheating and these have an impact on loop corrections due to the inflaton potential. Whilst corrections due to the supergravity couplings of the inflaton to Standard Model (MSSM) fields are negligible, we use Planck data to obtain interesting constraints on GUT bilinear couplings, vevs, and gauge boson masses that could be sharpened by future CMB measurements.

Universe

8 October 2026

(Left) The RG-improved effective potential as a function of 
  ϕ
 for various values of the inflaton decay coupling 
  
    y
    0
  
, compared to the tree-level potential. (Right) The spectral index 
  
    n
    s
  
 from the one-loop-corrected potential as a function of the decay coupling 
  
    y
    0
  
. The gray shaded region is the Planck constraint on 
  
    n
    s
  
 with its 
  
    ±
    2
    σ
  
 uncertainty, whilst the yellow band is the corresponding ACT constraint.
  • Article
  • Open Access

We present GalSpecCNN, a probabilistic deep-learning framework for estimating fiber-scale stellar mass (M*) and specific star formation rate (sSFR) from LAMOST galaxy spectra. The model uses a one-dimensional convolutional neural network to extract spectral features, followed by a probabilistic regression head that predicts a diagonal bivariate Gaussian distribution. Aleatoric uncertainty is modeled through the predicted variances, while epistemic uncertainty is approximated using Monte Carlo Dropout. On the test set, GalSpecCNN achieves residual scatters of 0.226 dex for M* and 0.319 dex for sSFR, with small mean residuals. The empirical coverages of the nominal 68% predictive intervals are 68.60% for M* and 71.58% for sSFR, indicating good overall calibration with mildly conservative coverage for sSFR. We apply the trained model to approximately 1.16×105 LAMOST DR7 galaxy spectra and construct a catalog of M* and sSFR estimates, together with their associated predictive intervals. This work provides a practical framework for uncertainty-aware estimation of galaxy physical properties from large spectroscopic surveys.

Universe

7 October 2026

Distributions of redshift and 
  
    S
    /
    
      N
      r
    
  
 for the learning sample and the main sample.

Highly Accessed Articles

News & Conferences

Latest Issues

Open for Submission

Journal Sections

New Insights into High-Energy Astrophysics, Galaxies, and Cosmology
Reprint

New Insights into High-Energy Astrophysics, Galaxies, and Cosmology

Celebrating the 10th Anniversary of the Re-establishment of the Department of Astronomy at Xiamen University (2012–2022)
Editors: Taotao Fang, Weimin Gu, Tong Liu, Beibei Liu
XFacebookLinkedIn
Universe - ISSN 2218-1997