physics

Varun Sahni

Varun Sahni is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Varun Sahni rather than just read about it. In short: Varun Bhisham Sahni (born 29 March 1956) is an Indian theoretical physicist, astrophysicist and a distinguished professor at the Inter-University Centre for Astronomy and Astrophysics. Known for his research on cosmology, Sahni is an elected fellow of all the three major Indian science academies viz.

Key takeaways

Varun Sahni belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Varun Sahni to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Varun Sahni from memory before moving on to harder problems.

Reference excerpt

Varun Bhisham Sahni (born 29 March 1956) is an Indian theoretical physicist, astrophysicist and a distinguished professor at the Inter-University Centre for Astronomy and Astrophysics. Known for his research on cosmology, Sahni is an elected fellow of all the three major Indian science academies viz. Indian Academy of Sciences, Indian National Science Academy and National Academy of Sciences, India. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards, for his contributions to physical sciences in 2000. Sahni is reported to have studied the universe, more specifically its large-scale structure, the early inflationary phase and cosmological constant. His achievements include the establishment of a cosmic no-hair theorem related to inflation, analysis of the universe structure using self-developed statistical methods, discovery of novel models of dark energy and dark matter, design of unified models of Inflation and dark energy and the elucidation of Big Bang theory using Braneworld physics. His studies have been documented by way of a number of articles and the online article repository of the Indian Academy of Sciences has listed 68 of them. Sahni is a member of the International Astronomical Union. He has delivered plenary addresses at many conferences and seminars; "Cosmology after the BOOMERANG experiment" delivered at the Astronomy Seminars 2000 of the Tata Institute of Fundamental Research and Frontiers of Cosmology and Gravitation (ICGC 2011) of the International Centre for Theoretical Sciences were two of them. The School of Applied Mathematical and Physical Sciences of the National Technical University of Athens has listed one of his talks on Dark matter and dark energy, delivered in March 2004, as the best cited among Aegean School talks. He is also a recipient of the Homi Bhabha Medal (2014) of the Indian National Science Academy.

Selected bibliography

Chapters Eleftherios Papantonopoulos; Varun Sahni (Chapter author) (7 January 2005). "Dark Matter and Dark Energy". The Physics of the Early Universe. Springer Science & Business Media. pp. 141–. ISBN 978-3-540-22712-0. {{cite book}}: |author2= has generic name (help)

Articles Varun Sahni, Peter Coles (1995). "Approximation Methods for Non-linear Gravitational Clustering". Phys. Rep. 262 (1–2): 1–135. arXiv:astro-ph/9505005. Bibcode:1995PhR...262....1S. doi:10.1016/0370-1573(95)00014-8. S2CID 119442929. Varun Sahni (2005). "Dark Matter and Dark Energy". In E. Papantonopoulos (ed.). The Physics of the Early Universe. Lecture Notes in Physics. Vol. 653. pp. 141–180. Bibcode:2005LNP...653....3T. doi:10.1007/b99562. ISBN 978-3-540-22712-0. Varun Sahni (2006). "Dark Energy". Journal of Physics: Conference Series. 31 (1): 115–122. Bibcode:2006JPhCS..31..115S. doi:10.1088/1742-6596/31/1/020. Varun Sahni, Arman Shafieloo, Alexei A. Starobinsky (2008). "Two new diagnostics of dark energy". Phys. Rev. D. 78 (10) 103502. arXiv:0807.3548. Bibcode:2008PhRvD..78j3502S. doi:10.1103/PhysRevD.78.103502. S2CID 118452106.{{cite journal}}: CS1 maint: multiple names: authors list (link) Varun Sahni (2014). "Ya. B. Zeldovich (1914-1987): Chemist, Nuclear Physicist, Cosmologist". Resonance. 16: 463–467. arXiv:1403.1537. Bibcode:2014arXiv1403.1537S.

Worked examples

Example 1 — a first encounter with Varun Sahni

Start with the simplest possible case. Write down what Varun Sahni claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Varun Sahni before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Varun Sahni ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Varun Sahni

In research: Varun Sahni appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Varun Sahni in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Varun Sahni is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1956 births, Fellows of the Indian Academy of Sciences, Fellows of the Indian National Science Academy, so understanding it makes those chapters shorter.
In everyday life: Look for Varun Sahni outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Varun Sahni in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Varun Sahni means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Varun Sahni out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Varun Sahni in simple terms?

Why does Varun Sahni matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Varun Sahni?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Varun Sahni.